HIR - Split hir.cpp a bit to allow hackery

2 files changed, 1062 insertions, 1046 deletions

diff --git a/src/hir/hir.cpp b/src/hir/hir.cpp
index fdd564d6..4b9aef10 100644
--- a/src/hir/hir.cpp
+++ b/src/hir/hir.cpp
@@ -150,932 +150,6 @@ uint32_t HIR::Enum::get_value(size_t idx) const
     }
 }
 
-namespace {
-    bool matches_genericpath(const ::HIR::GenericParams& params, const ::HIR::GenericPath& left, const ::HIR::GenericPath& right, ::HIR::t_cb_resolve_type ty_res, bool expand_generic);
-
-    bool matches_type_int(const ::HIR::GenericParams& params, const ::HIR::TypeRef& left,  const ::HIR::TypeRef& right_in, ::HIR::t_cb_resolve_type ty_res, bool expand_generic)
-    {
-        assert(! left.m_data.is_Infer() );
-        const auto& right = (right_in.m_data.is_Infer() || (right_in.m_data.is_Generic() && expand_generic) ? ty_res(right_in) : right_in);
-        if( right_in.m_data.is_Generic() )
-            expand_generic = false;
-
-        //DEBUG("left = " << left << ", right = " << right);
-
-        // TODO: What indicates what out of ty_res?
-
-        if( const auto* re = right.m_data.opt_Infer() )
-        {
-            //DEBUG("left = " << left << ", right = " << right);
-            switch(re->ty_class)
-            {
-            case ::HIR::InferClass::None:
-            case ::HIR::InferClass::Diverge:
-                //return left.m_data.is_Generic();
-                return true;
-            case ::HIR::InferClass::Integer:
-                TU_IFLET(::HIR::TypeRef::Data, left.m_data, Primitive, le,
-                    return is_integer(le);
-                )
-                else {
-                    return left.m_data.is_Generic();
-                }
-                break;
-            case ::HIR::InferClass::Float:
-                TU_IFLET(::HIR::TypeRef::Data, left.m_data, Primitive, le,
-                    return is_float(le);
-                )
-                else {
-                    return left.m_data.is_Generic();
-                }
-                break;
-            }
-            throw "";
-        }
-
-        // A local generic could match anything, leave that up to the caller
-        if( left.m_data.is_Generic() ) {
-            DEBUG("> Generic left, success");
-            return true;
-        }
-        // A local UfcsKnown can only be becuase it couldn't be expanded earlier, assume it could match
-        if( left.m_data.is_Path() && left.m_data.as_Path().path.m_data.is_UfcsKnown() ) {
-            // True?
-            //DEBUG("> UFCS Unknown left, success");
-            return true;
-        }
-
-        // If the RHS (provided) is generic, it can only match if it binds to a local type parameter
-        if( right.m_data.is_Generic() ) {
-            // TODO: This is handled above?
-            //DEBUG("> Generic right, only if left generic");
-            return left.m_data.is_Generic();
-        }
-        // If the RHS (provided) is generic, it can only match if it binds to a local type parameter
-        if( TU_TEST1(right.m_data, Path, .binding.is_Unbound()) ) {
-            //DEBUG("> UFCS Unknown right, fuzzy");
-            return true;
-        }
-
-        if( left.m_data.tag() != right.m_data.tag() ) {
-            //DEBUG("> Tag mismatch, failure");
-            return false;
-        }
-        TU_MATCH(::HIR::TypeRef::Data, (left.m_data, right.m_data), (le, re),
-        (Infer, assert(!"infer");),
-        (Diverge, return true; ),
-        (Primitive, return le == re;),
-        (Path,
-            if( le.path.m_data.tag() != re.path.m_data.tag() )
-                return false;
-            TU_MATCH_DEF(::HIR::Path::Data, (le.path.m_data, re.path.m_data), (ple, pre),
-            (
-                return false;
-                ),
-            (Generic,
-                return matches_genericpath(params, ple, pre, ty_res, expand_generic);
-                )
-            )
-            ),
-        (Generic,
-            throw "";
-            ),
-        (TraitObject,
-            if( !matches_genericpath(params, le.m_trait.m_path, re.m_trait.m_path, ty_res, expand_generic) )
-                return false;
-            if( le.m_markers.size() != re.m_markers.size() )
-                return false;
-            for(unsigned int i = 0; i < le.m_markers.size(); i ++)
-            {
-                const auto& lm = le.m_markers[i];
-                const auto& rm = re.m_markers[i];
-                if( !matches_genericpath(params, lm, rm, ty_res, expand_generic) )
-                    return false;
-            }
-            return true;
-            ),
-        (ErasedType,
-            throw "Unexpected ErasedType in matches_type_int";
-            ),
-        (Array,
-            if( ! matches_type_int(params, *le.inner, *re.inner, ty_res, expand_generic) )
-                return false;
-            if( le.size_val != re.size_val )
-                return false;
-            return true;
-            ),
-        (Slice,
-            return matches_type_int(params, *le.inner, *re.inner, ty_res, expand_generic);
-            ),
-        (Tuple,
-            if( le.size() != re.size() )
-                return false;
-            for( unsigned int i = 0; i < le.size(); i ++ )
-                if( !matches_type_int(params, le[i], re[i], ty_res, expand_generic) )
-                    return false;
-            return true;
-            ),
-        (Borrow,
-            if( le.type != re.type )
-                return false;
-            return matches_type_int(params, *le.inner, *re.inner, ty_res, expand_generic);
-            ),
-        (Pointer,
-            if( le.type != re.type )
-                return false;
-            return matches_type_int(params, *le.inner, *re.inner, ty_res, expand_generic);
-            ),
-        (Function,
-            if( le.is_unsafe != re.is_unsafe )
-                return false;
-            if( le.m_abi != re.m_abi )
-                return false;
-            if( le.m_arg_types.size() != re.m_arg_types.size() )
-                return false;
-            for( unsigned int i = 0; i < le.m_arg_types.size(); i ++ )
-                if( !matches_type_int(params, le.m_arg_types[i], re.m_arg_types[i], ty_res, expand_generic) )
-                    return false;
-            return matches_type_int(params, *le.m_rettype, *re.m_rettype, ty_res, expand_generic);
-            ),
-        (Closure,
-            return le.node == re.node;
-            )
-        )
-        return false;
-    }
-    bool matches_genericpath(const ::HIR::GenericParams& params, const ::HIR::GenericPath& left, const ::HIR::GenericPath& right, ::HIR::t_cb_resolve_type ty_res, bool expand_generic)
-    {
-        if( left.m_path.m_crate_name != right.m_path.m_crate_name )
-            return false;
-        if( left.m_path.m_components.size() != right.m_path.m_components.size() )
-            return false;
-        for(unsigned int i = 0; i < left.m_path.m_components.size(); i ++ )
-        {
-            if( left.m_path.m_components[i] != right.m_path.m_components[i] )
-                return false;
-        }
-
-        if( left.m_params.m_types.size() > 0 || right.m_params.m_types.size() > 0 )
-        {
-            // Count mismatch. Allow due to defaults.
-            if( left.m_params.m_types.size() != right.m_params.m_types.size() ) {
-                return true;
-                //TODO(Span(), "Match generic paths " << left << " and " << right << " - count mismatch");
-            }
-            for( unsigned int i = 0; i < right.m_params.m_types.size(); i ++ )
-            {
-                if( ! matches_type_int(params, left.m_params.m_types[i], right.m_params.m_types[i], ty_res, expand_generic) )
-                    return false;
-            }
-        }
-        return true;
-    }
-}
-
-//::HIR::TypeRef HIR::Function::make_ty(const Span& sp, const ::HIR::PathParams& params) const
-//{
-//    // TODO: Obtain function type for this function (i.e. a type that is specifically for this function)
-//    auto fcn_ty_data = ::HIR::FunctionType {
-//        m_is_unsafe,
-//        m_abi,
-//        box$( monomorphise_type(sp, m_params, params,  m_return) ),
-//        {}
-//        };
-//    fcn_ty_data.m_arg_types.reserve( m_args.size() );
-//    for(const auto& arg : m_args)
-//    {
-//        fcn_ty_data.m_arg_types.push_back( monomorphise_type(sp, m_params, params,  arg.second) );
-//    }
-//    return ::HIR::TypeRef( mv$(fcn_ty_data) );
-//}
-
-namespace {
-    bool is_unbounded_infer(const ::HIR::TypeRef& type) {
-        TU_IFLET( ::HIR::TypeRef::Data, type.m_data, Infer, e,
-            return e.ty_class == ::HIR::InferClass::None || e.ty_class == ::HIR::InferClass::Diverge;
-        )
-        else {
-            return false;
-        }
-    }
-}
-
-bool ::HIR::TraitImpl::matches_type(const ::HIR::TypeRef& type, ::HIR::t_cb_resolve_type ty_res) const
-{
-    // NOTE: Don't return any impls when the type is an unbouned ivar. Wouldn't be able to pick anything anyway
-    // TODO: For `Unbound`, it could be valid, if the target is a generic.
-    // - Pure infer could also be useful (for knowing if there's any other potential impls)
-    if( is_unbounded_infer(type) || TU_TEST1(type.m_data, Path, .binding.is_Unbound()) ) {
-        return false;
-    }
-    return matches_type_int(m_params, m_type, type, ty_res, true);
-}
-bool ::HIR::TypeImpl::matches_type(const ::HIR::TypeRef& type, ::HIR::t_cb_resolve_type ty_res) const
-{
-    if( is_unbounded_infer(type) || TU_TEST1(type.m_data, Path, .binding.is_Unbound()) ) {
-        return false;
-    }
-    return matches_type_int(m_params, m_type, type, ty_res, true);
-}
-bool ::HIR::MarkerImpl::matches_type(const ::HIR::TypeRef& type, ::HIR::t_cb_resolve_type ty_res) const
-{
-    if( is_unbounded_infer(type) || TU_TEST1(type.m_data, Path, .binding.is_Unbound()) ) {
-        return false;
-    }
-    return matches_type_int(m_params, m_type, type, ty_res, true);
-}
-
-namespace {
-
-    struct TypeOrdSpecific_MixedOrdering
-    {
-    };
-
-    ::Ordering typelist_ord_specific(const Span& sp, const ::std::vector<::HIR::TypeRef>& left, const ::std::vector<::HIR::TypeRef>& right);
-
-    ::Ordering type_ord_specific(const Span& sp, const ::HIR::TypeRef& left, const ::HIR::TypeRef& right)
-    {
-        // TODO: What happens if you get `impl<T> Foo<T> for T` vs `impl<T,U> Foo<U> for T`
-
-        // A generic can't be more specific than any other type we can see
-        // - It's equally as specific as another Generic, so still false
-        if( left.m_data.is_Generic() ) {
-            return right.m_data.is_Generic() ? ::OrdEqual : ::OrdLess;
-        }
-        // - A generic is always less specific than anything but itself (handled above)
-        if( right.m_data.is_Generic() ) {
-            return ::OrdGreater;
-        }
-
-        TU_MATCH(::HIR::TypeRef::Data, (left.m_data), (le),
-        (Generic,
-            throw "";
-            ),
-        (Infer,
-            BUG(sp, "Hit infer");
-            ),
-        (Diverge,
-            BUG(sp, "Hit diverge");
-            ),
-        (Closure,
-            BUG(sp, "Hit closure");
-            ),
-        (Primitive,
-            TU_IFLET(::HIR::TypeRef::Data, right.m_data, Primitive, re,
-                if( le != re )
-                    BUG(sp, "Mismatched types - " << left << " and " << right);
-                return ::OrdEqual;
-            )
-            else {
-                BUG(sp, "Mismatched types - " << left << " and " << right);
-            }
-            ),
-        (Path,
-            if( !right.m_data.is_Path() || le.path.m_data.tag() != right.m_data.as_Path().path.m_data.tag() )
-                BUG(sp, "Mismatched types - " << left << " and " << right);
-            TU_MATCHA( (le.path.m_data, right.m_data.as_Path().path.m_data), (lpe, rpe),
-            (Generic,
-                if( lpe.m_path != rpe.m_path )
-                    BUG(sp, "Mismatched types - " << left << " and " << right);
-                return typelist_ord_specific(sp, lpe.m_params.m_types, rpe.m_params.m_types);
-                ),
-            (UfcsUnknown,
-                ),
-            (UfcsKnown,
-                ),
-            (UfcsInherent,
-                )
-            )
-            TODO(sp, "Path - " << le.path << " and " << right);
-            ),
-        (TraitObject,
-            ASSERT_BUG(sp, right.m_data.is_TraitObject(), "Mismatched types - "<< left << " vs " << right);
-            const auto& re = right.m_data.as_TraitObject();
-            ASSERT_BUG(sp, le.m_trait.m_path.m_path == re.m_trait.m_path.m_path, "Mismatched types - "<< left << " vs " << right);
-            ASSERT_BUG(sp, le.m_markers.size() == re.m_markers.size(), "Mismatched types - "<< left << " vs " << right);
-
-            auto ord = typelist_ord_specific(sp, le.m_trait.m_path.m_params.m_types, re.m_trait.m_path.m_params.m_types);
-            if( ord != ::OrdEqual )
-                return ord;
-            for(size_t i = 0; i < le.m_markers.size(); i ++)
-            {
-                ASSERT_BUG(sp, le.m_markers[i].m_path == re.m_markers[i].m_path, "Mismatched types - " << left << " vs " << right);
-                ord = typelist_ord_specific(sp, le.m_markers[i].m_params.m_types, re.m_markers[i].m_params.m_types);
-                if(ord != ::OrdEqual)
-                    return ord;
-            }
-            return ::OrdEqual;
-            ),
-        (ErasedType,
-            TODO(sp, "ErasedType - " << left);
-            ),
-        (Function,
-            TU_IFLET(::HIR::TypeRef::Data, right.m_data, Function, re,
-                TODO(sp, "Function");
-                //return typelist_ord_specific(sp, le.arg_types, re.arg_types);
-            )
-            else {
-                BUG(sp, "Mismatched types - " << left << " and " << right);
-            }
-            ),
-        (Tuple,
-            TU_IFLET(::HIR::TypeRef::Data, right.m_data, Tuple, re,
-                return typelist_ord_specific(sp, le, re);
-            )
-            else {
-                BUG(sp, "Mismatched types - " << left << " and " << right);
-            }
-            ),
-        (Slice,
-            TU_IFLET(::HIR::TypeRef::Data, right.m_data, Slice, re,
-                return type_ord_specific(sp, *le.inner, *re.inner);
-            )
-            else {
-                BUG(sp, "Mismatched types - " << left << " and " << right);
-            }
-            ),
-        (Array,
-            TU_IFLET(::HIR::TypeRef::Data, right.m_data, Array, re,
-                if( le.size_val != re.size_val )
-                    BUG(sp, "Mismatched types - " << left << " and " << right);
-                return type_ord_specific(sp, *le.inner, *re.inner);
-            )
-            else {
-                BUG(sp, "Mismatched types - " << left << " and " << right);
-            }
-            ),
-        (Pointer,
-            TU_IFLET(::HIR::TypeRef::Data, right.m_data, Pointer, re,
-                if( le.type != re.type )
-                    BUG(sp, "Mismatched types - " << left << " and " << right);
-                return type_ord_specific(sp, *le.inner, *re.inner);
-            )
-            else {
-                BUG(sp, "Mismatched types - " << left << " and " << right);
-            }
-            ),
-        (Borrow,
-            TU_IFLET(::HIR::TypeRef::Data, right.m_data, Borrow, re,
-                if( le.type != re.type )
-                    BUG(sp, "Mismatched types - " << left << " and " << right);
-                return type_ord_specific(sp, *le.inner, *re.inner);
-            )
-            else {
-                BUG(sp, "Mismatched types - " << left << " and " << right);
-            }
-            )
-        )
-        throw "Fell off end of type_ord_specific";
-    }
-
-    ::Ordering typelist_ord_specific(const Span& sp, const ::std::vector<::HIR::TypeRef>& le, const ::std::vector<::HIR::TypeRef>& re)
-    {
-        auto rv = ::OrdEqual;
-        assert(le.size() == re.size());
-        for(unsigned int i = 0; i < le.size(); i ++) {
-            auto a = type_ord_specific(sp, le[i], re[i]);
-            if( a != ::OrdEqual ) {
-                if( rv != ::OrdEqual && a != rv )
-                {
-                    DEBUG("Inconsistent ordering between type lists - i=" << i << " [" << le << "] vs [" << re << "]");
-                    throw TypeOrdSpecific_MixedOrdering {};
-                }
-                rv = a;
-            }
-        }
-        return rv;
-    }
-}
-
-namespace {
-    void add_bound_from_trait(::std::vector< ::HIR::GenericBound>& rv,  const ::HIR::TypeRef& type, const ::HIR::TraitPath& cur_trait)
-    {
-        static Span sp;
-        assert( cur_trait.m_trait_ptr );
-        const auto& tr = *cur_trait.m_trait_ptr;
-        auto monomorph_cb = monomorphise_type_get_cb(sp, &type, &cur_trait.m_path.m_params, nullptr);
-
-        for(const auto& trait_path_raw : tr.m_all_parent_traits)
-        {
-            // 1. Monomorph
-            auto trait_path_mono = monomorphise_traitpath_with(sp, trait_path_raw, monomorph_cb, false);
-            // 2. Add
-            rv.push_back( ::HIR::GenericBound::make_TraitBound({ type.clone(), mv$(trait_path_mono) }) );
-        }
-
-        // TODO: Add traits from `Self: Foo` bounds?
-        // TODO: Move associated types to the source trait.
-    }
-    ::std::vector< ::HIR::GenericBound> flatten_bounds(const ::std::vector<::HIR::GenericBound>& bounds)
-    {
-        ::std::vector< ::HIR::GenericBound >    rv;
-        for(const auto& b : bounds)
-        {
-            TU_MATCHA( (b), (be),
-            (Lifetime,
-                rv.push_back( ::HIR::GenericBound(be) );
-                ),
-            (TypeLifetime,
-                rv.push_back( ::HIR::GenericBound::make_TypeLifetime({ be.type.clone(), be.valid_for }) );
-                ),
-            (TraitBound,
-                rv.push_back( ::HIR::GenericBound::make_TraitBound({ be.type.clone(), be.trait.clone() }) );
-                add_bound_from_trait(rv,  be.type, be.trait);
-                ),
-            (TypeEquality,
-                rv.push_back( ::HIR::GenericBound::make_TypeEquality({ be.type.clone(), be.other_type.clone() }) );
-                )
-            )
-        }
-        ::std::sort(rv.begin(), rv.end(), [](const auto& a, const auto& b){ return ::ord(a,b) == OrdLess; });
-        return rv;
-    }
-}
-
-bool ::HIR::TraitImpl::more_specific_than(const ::HIR::TraitImpl& other) const
-{
-    static const Span   _sp;
-    const Span& sp = _sp;
-    TRACE_FUNCTION;
-    //DEBUG("this  = " << *this);
-    //DEBUG("other = " << other);
-
-    // >> https://github.com/rust-lang/rfcs/blob/master/text/1210-impl-specialization.md#defining-the-precedence-rules
-    // 1. If this->m_type is less specific than other.m_type: return false
-    try
-    {
-        auto ord = type_ord_specific(sp, this->m_type, other.m_type);
-        // If `*this` < `other` : false
-        if( ord != ::OrdEqual ) {
-            DEBUG("- Type " << this->m_type << " " << (ord == ::OrdLess ? "less" : "more") << " specific than " << other.m_type);
-            return ord == ::OrdGreater;
-        }
-        // 2. If any in te.impl->m_params is less specific than oe.impl->m_params: return false
-        ord = typelist_ord_specific(sp, this->m_trait_args.m_types, other.m_trait_args.m_types);
-        if( ord != ::OrdEqual ) {
-            DEBUG("- Trait arguments " << (ord == ::OrdLess ? "less" : "more") << " specific");
-            return ord == ::OrdGreater;
-        }
-    }
-    catch(const TypeOrdSpecific_MixedOrdering& e)
-    {
-        BUG(sp, "Mixed ordering in more_specific_than");
-    }
-
-    //if( other.m_params.m_bounds.size() == 0 ) {
-    //    DEBUG("- Params (none in other, some in this)");
-    //    return m_params.m_bounds.size() > 0;
-    //}
-    // 3. Compare bound set, if there is a rule in oe that is missing from te; return false
-    // TODO: Cache these lists (calculate after outer typecheck?)
-    auto bounds_t = flatten_bounds(m_params.m_bounds);
-    auto bounds_o = flatten_bounds(other.m_params.m_bounds);
-
-    DEBUG("bounds_t = " << bounds_t);
-    DEBUG("bounds_o = " << bounds_o);
-
-    // If there are less bounds in this impl, it can't be more specific.
-    if( bounds_t.size() < bounds_o.size() )
-    {
-        DEBUG("Bound count");
-        return false;
-    }
-
-    auto it_t = bounds_t.begin();
-    auto it_o = bounds_o.begin();
-    while( it_t != bounds_t.end() && it_o != bounds_o.end() )
-    {
-        auto cmp = ::ord(*it_t, *it_o);
-        if( cmp == OrdEqual )
-        {
-            ++it_t;
-            ++it_o;
-            continue ;
-        }
-
-        // If the two bounds are similar
-        if( it_t->tag() == it_o->tag() && it_t->is_TraitBound() )
-        {
-            const auto& b_t = it_t->as_TraitBound();
-            const auto& b_o = it_o->as_TraitBound();
-            // Check if the type is equal
-            if( b_t.type == b_o.type && b_t.trait.m_path.m_path == b_o.trait.m_path.m_path )
-            {
-                const auto& params_t = b_t.trait.m_path.m_params;
-                const auto& params_o = b_o.trait.m_path.m_params;
-                switch( typelist_ord_specific(sp, params_t.m_types, params_o.m_types) )
-                {
-                case ::OrdLess: return false;
-                case ::OrdGreater: return true;
-                case ::OrdEqual:    break;
-                }
-                // TODO: Find cases where there's `T: Foo<T>` and `T: Foo<U>`
-                for(unsigned int i = 0; i < params_t.m_types.size(); i ++ )
-                {
-                    if( params_t.m_types[i] != params_o.m_types[i] && params_t.m_types[i] == b_t.type )
-                    {
-                        return true;
-                    }
-                }
-                TODO(sp, *it_t << " ?= " << *it_o);
-            }
-        }
-
-        if( cmp == OrdLess )
-        {
-            ++ it_t;
-        }
-        else
-        {
-            //++ it_o;
-            return false;
-        }
-    }
-    if( it_t != bounds_t.end() )
-    {
-        return true;
-    }
-    else
-    {
-        return false;
-    }
-}
-
-// Returns `true` if the two impls overlap in the types they will accept
-bool ::HIR::TraitImpl::overlaps_with(const Crate& crate, const ::HIR::TraitImpl& other) const
-{
-    // TODO: Pre-calculate impl trees (with pointers to parent impls)
-    struct H {
-        static bool types_overlap(const ::HIR::PathParams& a, const ::HIR::PathParams& b)
-        {
-            for(unsigned int i = 0; i < ::std::min(a.m_types.size(), b.m_types.size()); i ++)
-            {
-                if( ! H::types_overlap(a.m_types[i], b.m_types[i]) )
-                    return false;
-            }
-            return true;
-        }
-        static bool types_overlap(const ::HIR::TypeRef& a, const ::HIR::TypeRef& b)
-        {
-            static Span sp;
-            //DEBUG("(" << a << "," << b << ")");
-            if( a.m_data.is_Generic() || b.m_data.is_Generic() )
-                return true;
-            // TODO: Unbound/Opaque paths?
-            if( a.m_data.tag() != b.m_data.tag() )
-                return false;
-            TU_MATCHA( (a.m_data, b.m_data), (ae, be),
-            (Generic,
-                ),
-            (Infer,
-                ),
-            (Diverge,
-                ),
-            (Closure,
-                BUG(sp, "Hit closure");
-                ),
-            (Primitive,
-                if( ae != be )
-                    return false;
-                ),
-            (Path,
-                if( ae.path.m_data.tag() != be.path.m_data.tag() )
-                    return false;
-                TU_MATCHA( (ae.path.m_data, be.path.m_data), (ape, bpe),
-                (Generic,
-                    if( ape.m_path != bpe.m_path )
-                        return false;
-                    return H::types_overlap(ape.m_params, bpe.m_params);
-                    ),
-                (UfcsUnknown,
-                    ),
-                (UfcsKnown,
-                    ),
-                (UfcsInherent,
-                    )
-                )
-                TODO(sp, "Path - " << ae.path << " and " << be.path);
-                ),
-            (TraitObject,
-                if( ae.m_trait.m_path.m_path != be.m_trait.m_path.m_path )
-                    return false;
-                if( !H::types_overlap(ae.m_trait.m_path.m_params, be.m_trait.m_path.m_params) )
-                    return false;
-                // Marker traits only overlap if the lists are the same (with overlap)
-                if( ae.m_markers.size() != be.m_markers.size() )
-                    return false;
-                for(size_t i = 0; i < ae.m_markers.size(); i++)
-                {
-                    if( ae.m_markers[i].m_path != be.m_markers[i].m_path )
-                        return false;
-                    if( !H::types_overlap(ae.m_markers[i].m_params, be.m_markers[i].m_params) )
-                        return false;
-                }
-                return true;
-                ),
-            (ErasedType,
-                TODO(sp, "ErasedType - " << a);
-                ),
-            (Function,
-                if( ae.is_unsafe != be.is_unsafe )
-                    return false;
-                if( ae.m_abi != be.m_abi )
-                    return false;
-                if( ae.m_arg_types.size() != be.m_arg_types.size() )
-                    return false;
-                for(unsigned int i = 0; i < ae.m_arg_types.size(); i ++)
-                {
-                    if( ! H::types_overlap(ae.m_arg_types[i], be.m_arg_types[i]) )
-                        return false;
-                }
-                ),
-            (Tuple,
-                if( ae.size() != be.size() )
-                    return false;
-                for(unsigned int i = 0; i < ae.size(); i ++)
-                {
-                    if( ! H::types_overlap(ae[i], be[i]) )
-                        return false;
-                }
-                ),
-            (Slice,
-                return H::types_overlap( *ae.inner, *be.inner );
-                ),
-            (Array,
-                if( ae.size_val != be.size_val )
-                    return false;
-                return H::types_overlap( *ae.inner, *be.inner );
-                ),
-            (Pointer,
-                if( ae.type != be.type )
-                    return false;
-                return H::types_overlap( *ae.inner, *be.inner );
-                ),
-            (Borrow,
-                if( ae.type != be.type )
-                    return false;
-                return H::types_overlap( *ae.inner, *be.inner );
-                )
-            )
-            return true;
-        }
-    };
-
-    // Quick Check: If the types are equal, they do overlap
-    if(this->m_type == other.m_type && this->m_trait_args == other.m_trait_args)
-    {
-        return true;
-    }
-
-    // 1. Are the impl types of the same form (or is one generic)
-    if( ! H::types_overlap(this->m_type, other.m_type) )
-        return false;
-    if( ! H::types_overlap(this->m_trait_args, other.m_trait_args) )
-        return false;
-
-    DEBUG("TODO: Handle potential overlap (when not exactly equal)");
-    //return this->m_type == other.m_type && this->m_trait_args == other.m_trait_args;
-    Span    sp;
-
-    // TODO: Use `type_ord_specific` but treat any case of mixed ordering as this returning `false`
-    try
-    {
-        type_ord_specific(sp, this->m_type, other.m_type);
-        typelist_ord_specific(sp, this->m_trait_args.m_types, other.m_trait_args.m_types);
-    }
-    catch(const TypeOrdSpecific_MixedOrdering& /*e*/)
-    {
-        return false;
-    }
-
-    // TODO: Detect `impl<T> Foo<T> for Bar<T>` vs `impl<T> Foo<&T> for Bar<T>`
-    // > Create values for impl params from the type, then check if the trait params are compatible
-    // > Requires two lists, and telling which one to use by the end
-    auto cb_ident = [](const ::HIR::TypeRef& x)->const ::HIR::TypeRef& { return x; };
-    bool is_reversed = false;
-    ::std::vector<const ::HIR::TypeRef*>    impl_tys;
-    auto cb_match = [&](unsigned int idx, const auto& /*name*/, const ::HIR::TypeRef& x)->::HIR::Compare {
-        assert(idx < impl_tys.size());
-        if( impl_tys.at(idx) )
-        {
-            DEBUG("Compare " << x << " and " << *impl_tys.at(idx));
-            return (x == *impl_tys.at(idx) ? ::HIR::Compare::Equal : ::HIR::Compare::Unequal);
-        }
-        else
-        {
-            impl_tys.at(idx) = &x;
-            return ::HIR::Compare::Equal;
-        }
-        };
-    impl_tys.resize( this->m_params.m_types.size() );
-    if( ! this->m_type.match_test_generics(sp, other.m_type, cb_ident, cb_match) )
-    {
-        DEBUG("- Type mismatch, try other ordering");
-        is_reversed = true;
-        impl_tys.clear(); impl_tys.resize( other.m_params.m_types.size() );
-        if( !other.m_type.match_test_generics(sp, this->m_type, cb_ident, cb_match) )
-        {
-            DEBUG("- Type mismatch in both orderings");
-            return false;
-        }
-        if( other.m_trait_args.match_test_generics_fuzz(sp, this->m_trait_args, cb_ident, cb_match) != ::HIR::Compare::Equal )
-        {
-            DEBUG("- Params mismatch");
-            return false;
-        }
-        // Matched with second ording
-    }
-    else if( this->m_trait_args.match_test_generics_fuzz(sp, other.m_trait_args, cb_ident, cb_match) != ::HIR::Compare::Equal )
-    {
-        DEBUG("- Param mismatch, try other ordering");
-        is_reversed = true;
-        impl_tys.clear(); impl_tys.resize( other.m_params.m_types.size() );
-        if( !other.m_type.match_test_generics(sp, this->m_type, cb_ident, cb_match) )
-        {
-            DEBUG("- Type mismatch in alt ordering");
-            return false;
-        }
-        if( other.m_trait_args.match_test_generics_fuzz(sp, this->m_trait_args, cb_ident, cb_match) != ::HIR::Compare::Equal )
-        {
-            DEBUG("- Params mismatch in alt ordering");
-            return false;
-        }
-        // Matched with second ordering
-    }
-    else
-    {
-        // Matched with first ordering
-    }
-
-    struct H2 {
-        static const ::HIR::TypeRef& monomorph(const Span& sp, const ::HIR::TypeRef& in_ty, const ::std::vector<const ::HIR::TypeRef*>& args, ::HIR::TypeRef& tmp)
-        {
-            if( ! monomorphise_type_needed(in_ty) ) {
-                return in_ty;
-            }
-            else if( const auto* tep = in_ty.m_data.opt_Generic() ) {
-                ASSERT_BUG(sp, tep->binding < args.size(), "");
-                ASSERT_BUG(sp, args[tep->binding], "");
-                return *args[tep->binding];
-            }
-            else {
-                auto monomorph_cb = [&](const auto& t)->const auto& {
-                    const auto& te = t.m_data.as_Generic();
-                    assert(te.binding < args.size());
-                    ASSERT_BUG(sp, te.binding < args.size(), "");
-                    ASSERT_BUG(sp, args[te.binding], "");
-                    return *args[te.binding];
-                    };
-                tmp = monomorphise_type_with(sp, in_ty, monomorph_cb);
-                // TODO: EAT?
-                return tmp;
-            }
-        }
-        static const ::HIR::TraitPath& monomorph(const Span& sp, const ::HIR::TraitPath& in, const ::std::vector<const ::HIR::TypeRef*>& args, ::HIR::TraitPath& tmp)
-        {
-            if( ! monomorphise_traitpath_needed(in) ) {
-                return in;
-            }
-            else {
-                auto monomorph_cb = [&](const auto& t)->const auto& {
-                    const auto& te = t.m_data.as_Generic();
-                    assert(te.binding < args.size());
-                    ASSERT_BUG(sp, te.binding < args.size(), "");
-                    ASSERT_BUG(sp, args[te.binding], "");
-                    return *args[te.binding];
-                    };
-                tmp = monomorphise_traitpath_with(sp, in, monomorph_cb, true);
-                // TODO: EAT?
-                return tmp;
-            }
-        }
-        static bool check_bounds(const ::HIR::Crate& crate, const ::HIR::TraitImpl& id, const ::std::vector<const ::HIR::TypeRef*>& args, const ::HIR::TraitImpl& g_src)
-        {
-            TRACE_FUNCTION;
-            static Span sp;
-            for(const auto& tb : id.m_params.m_bounds)
-            {
-                if(tb.is_TraitBound())
-                {
-                    ::HIR::TypeRef  tmp_ty;
-                    ::HIR::TraitPath    tmp_tp;
-                    const auto& ty = H2::monomorph(sp, tb.as_TraitBound().type, args, tmp_ty);
-                    const auto& trait = H2::monomorph(sp, tb.as_TraitBound().trait, args, tmp_tp);;
-
-                    // Determine if `ty` would be bounded (it's an ATY or generic)
-                    if( ty.m_data.is_Generic() ) {
-                        bool found = false;
-                        for(const auto& bound : g_src.m_params.m_bounds)
-                        {
-                            if(const auto* be = bound.opt_TraitBound())
-                            {
-                                if( be->type != ty ) continue;
-                                if( be->trait != trait ) continue;
-                                found = true;
-                            }
-                        }
-                        if( !found )
-                        {
-                            DEBUG("No matching bound for " << ty << " : " << trait << " in source bounds - " << g_src.m_params.fmt_bounds());
-                            return false;
-                        }
-                    }
-                    else if( TU_TEST1(ty.m_data, Path, .binding.is_Opaque()) ) {
-                        TODO(Span(), "Check bound " << ty << " : " << trait << " in source bounds or trait bounds");
-                    }
-                    else {
-                        // Search the crate for an impl
-                        bool rv = crate.find_trait_impls(trait.m_path.m_path, ty, [](const auto&t)->const auto&{ return t; }, [&](const ::HIR::TraitImpl& ti)->bool {
-                                DEBUG("impl" << ti.m_params.fmt_args() << " " << trait.m_path.m_path << ti.m_trait_args << " for " << ti.m_type << ti.m_params.fmt_bounds());
-
-                                ::std::vector<const ::HIR::TypeRef*>   impl_tys { ti.m_params.m_types.size() };
-                                auto cb_ident = [](const ::HIR::TypeRef& x)->const ::HIR::TypeRef& { return x; };
-                                auto cb_match = [&](unsigned int idx, const auto& /*name*/, const ::HIR::TypeRef& x)->::HIR::Compare {
-                                    assert(idx < impl_tys.size());
-                                    if( impl_tys.at(idx) )
-                                    {
-                                        DEBUG("Compare " << x << " and " << *impl_tys.at(idx));
-                                        return (x == *impl_tys.at(idx) ? ::HIR::Compare::Equal : ::HIR::Compare::Unequal);
-                                    }
-                                    else
-                                    {
-                                        impl_tys.at(idx) = &x;
-                                        return ::HIR::Compare::Equal;
-                                    }
-                                    };
-                                // 1. Triple-check the type matches (and get generics)
-                                if( ! ti.m_type.match_test_generics(sp, ty, cb_ident, cb_match) )
-                                    return false;
-                                // 2. Check trait params
-                                assert(trait.m_path.m_params.m_types.size() == ti.m_trait_args.m_types.size());
-                                for(size_t i = 0; i < trait.m_path.m_params.m_types.size(); i ++)
-                                {
-                                    if( !ti.m_trait_args.m_types[i].match_test_generics(sp, trait.m_path.m_params.m_types[i], cb_ident, cb_match) )
-                                        return false;
-                                }
-                                // 3. Check bounds on the impl
-                                if( !H2::check_bounds(crate, ti, impl_tys, g_src) )
-                                    return false;
-                                // 4. Check ATY bounds on the trait path
-                                for(const auto& atyb : trait.m_type_bounds)
-                                {
-                                    const auto& aty = ti.m_types.at(atyb.first);
-                                    if( !aty.data.match_test_generics(sp, atyb.second, cb_ident, cb_match) )
-                                        return false;
-                                }
-                                // All those pass? It's good.
-                                return true;
-                            });
-                        if( !rv )
-                        {
-                            return false;
-                        }
-                    }
-                }
-                else
-                {
-                    // TODO: Other bound types?
-                }
-            }
-            // No bounds failed, it's good
-            return true;
-        }
-    };
-
-    // The two impls could overlap, pending on trait bounds
-    if(is_reversed)
-    {
-        DEBUG("(reversed) impl params " << FMT_CB(os,
-                for(auto* p : impl_tys)
-                {
-                    if(p)
-                        os << *p;
-                    else
-                        os << "?";
-                    os << ",";
-                }
-                ));
-        // Check bounds on `other` using these params
-        // TODO: Take a callback that does the checks. Or somehow return a "maybe overlaps" result?
-        return H2::check_bounds(crate, other, impl_tys, *this);
-    }
-    else
-    {
-        DEBUG("impl params " << FMT_CB(os,
-                for(auto* p : impl_tys)
-                {
-                    if(p)
-                        os << *p;
-                    else
-                        os << "?";
-                    os << ",";
-                }
-                ));
-        // Check bounds on `*this`
-        return H2::check_bounds(crate, *this, impl_tys, other);
-    }
-}
-
 
 const ::HIR::SimplePath& ::HIR::Crate::get_lang_item_path(const Span& sp, const char* name) const
 {
@@ -1248,123 +322,3 @@ const ::HIR::Function& ::HIR::Crate::get_function_by_path(const Span& sp, const
     }
 }
 
-bool ::HIR::Crate::find_trait_impls(const ::HIR::SimplePath& trait, const ::HIR::TypeRef& type, t_cb_resolve_type ty_res, ::std::function<bool(const ::HIR::TraitImpl&)> callback) const
-{
-    auto its = this->m_trait_impls.equal_range( trait );
-    for( auto it = its.first; it != its.second; ++ it )
-    {
-        const auto& impl = it->second;
-        if( impl.matches_type(type, ty_res) ) {
-            if( callback(impl) ) {
-                return true;
-            }
-        }
-    }
-    for( const auto& ec : this->m_ext_crates )
-    {
-        if( ec.second.m_data->find_trait_impls(trait, type, ty_res, callback) ) {
-            return true;
-        }
-    }
-    return false;
-}
-bool ::HIR::Crate::find_auto_trait_impls(const ::HIR::SimplePath& trait, const ::HIR::TypeRef& type, t_cb_resolve_type ty_res, ::std::function<bool(const ::HIR::MarkerImpl&)> callback) const
-{
-    auto its = this->m_marker_impls.equal_range( trait );
-    for( auto it = its.first; it != its.second; ++ it )
-    {
-        const auto& impl = it->second;
-        if( impl.matches_type(type, ty_res) ) {
-            if( callback(impl) ) {
-                return true;
-            }
-        }
-    }
-    for( const auto& ec : this->m_ext_crates )
-    {
-        if( ec.second.m_data->find_auto_trait_impls(trait, type, ty_res, callback) ) {
-            return true;
-        }
-    }
-    return false;
-}
-bool ::HIR::Crate::find_type_impls(const ::HIR::TypeRef& type, t_cb_resolve_type ty_res, ::std::function<bool(const ::HIR::TypeImpl&)> callback) const
-{
-    // TODO: Restrict which crate is searched based on the type.
-    for( const auto& impl : this->m_type_impls )
-    {
-        if( impl.matches_type(type, ty_res) ) {
-            if( callback(impl) ) {
-                return true;
-            }
-        }
-    }
-    for( const auto& ec : this->m_ext_crates )
-    {
-        //DEBUG("- " << ec.first);
-        if( ec.second.m_data->find_type_impls(type, ty_res, callback) ) {
-            return true;
-        }
-    }
-    return false;
-}
-
-const ::MIR::Function* HIR::Crate::get_or_gen_mir(const ::HIR::ItemPath& ip, const ::HIR::ExprPtr& ep, const ::HIR::Function::args_t& args, const ::HIR::TypeRef& ret_ty) const
-{
-    if( !ep )
-    {
-        return &*ep.m_mir;
-    }
-    else
-    {
-        if( !ep.m_mir )
-        {
-            TRACE_FUNCTION_F(ip);
-            ASSERT_BUG(Span(), ep.m_state, "No ExprState for " << ip);
-
-            auto& ep_mut = const_cast<::HIR::ExprPtr&>(ep);
-
-            // Ensure typechecked
-            if( ep.m_state->stage < ::HIR::ExprState::Stage::Typecheck )
-            {
-                if( ep.m_state->stage == ::HIR::ExprState::Stage::TypecheckRequest )
-                    ERROR(Span(), E0000, "Loop in constant evaluation");
-                ep.m_state->stage = ::HIR::ExprState::Stage::TypecheckRequest;
-
-                // TODO: Set debug/timing stage
-                //Debug_SetStagePre("HIR Typecheck");
-                // - Can store that on the Expr, OR get it from the item path
-                typeck::ModuleState ms { const_cast<::HIR::Crate&>(*this) };
-                ms.m_impl_generics = ep.m_state->m_impl_generics;
-                ms.m_item_generics = ep.m_state->m_item_generics;
-                ms.m_traits = ep.m_state->m_traits;
-                Typecheck_Code(ms, const_cast<::HIR::Function::args_t&>(args), ret_ty, ep_mut);
-                //Debug_SetStagePre("Expand HIR Annotate");
-                HIR_Expand_AnnotateUsage_Expr(*this, ep_mut);
-                //Debug_SetStagePre("Expand HIR Closures");
-                HIR_Expand_Closures_Expr(*this, ep_mut);
-                //Debug_SetStagePre("Expand HIR Calls");
-                HIR_Expand_UfcsEverything_Expr(*this, ep_mut);
-                //Debug_SetStagePre("Expand HIR Reborrows");
-                HIR_Expand_Reborrows_Expr(*this, ep_mut);
-                //Debug_SetStagePre("Expand HIR ErasedType");
-                //HIR_Expand_ErasedType(*this, ep_mut);    // - Maybe?
-                //Typecheck_Expressions_Validate(*hir_crate);
-
-                ep.m_state->stage = ::HIR::ExprState::Stage::Typecheck;
-            }
-            // Generate MIR
-            if( ep.m_state->stage < ::HIR::ExprState::Stage::Mir )
-            {
-                if( ep.m_state->stage == ::HIR::ExprState::Stage::MirRequest )
-                    ERROR(Span(), E0000, "Loop in constant evaluation");
-                ep.m_state->stage = ::HIR::ExprState::Stage::MirRequest;
-                //Debug_SetStage("Lower MIR");
-                HIR_GenerateMIR_Expr(*this, ip, ep_mut, args, ret_ty);
-                ep.m_state->stage = ::HIR::ExprState::Stage::Mir;
-            }
-            assert(ep.m_mir);
-        }
-        return &*ep.m_mir;
-    }
-}
diff --git a/src/hir/hir_ops.cpp b/src/hir/hir_ops.cpp
new file mode 100644
index 00000000..a082becd
--- /dev/null
+++ b/src/hir/hir_ops.cpp
@@ -0,0 +1,1062 @@
+/*
+ * MRustC - Rust Compiler
+ * - By John Hodge (Mutabah/thePowersGang)
+ *
+ * hir/hir_ops.cpp
+ * - Complex operations on the HIR
+ */
+#include "hir.hpp"
+#include <algorithm>
+#include <hir_typeck/common.hpp>
+#include <hir_typeck/expr_visit.hpp>    // for invoking typecheck
+#include "item_path.hpp"
+#include "expr_state.hpp"
+#include <hir_expand/main_bindings.hpp>
+#include <mir/main_bindings.hpp>
+
+namespace {
+    bool matches_genericpath(const ::HIR::GenericParams& params, const ::HIR::GenericPath& left, const ::HIR::GenericPath& right, ::HIR::t_cb_resolve_type ty_res, bool expand_generic);
+
+    bool matches_type_int(const ::HIR::GenericParams& params, const ::HIR::TypeRef& left,  const ::HIR::TypeRef& right_in, ::HIR::t_cb_resolve_type ty_res, bool expand_generic)
+    {
+        assert(! left.m_data.is_Infer() );
+        const auto& right = (right_in.m_data.is_Infer() || (right_in.m_data.is_Generic() && expand_generic) ? ty_res(right_in) : right_in);
+        if( right_in.m_data.is_Generic() )
+            expand_generic = false;
+
+        //DEBUG("left = " << left << ", right = " << right);
+
+        // TODO: What indicates what out of ty_res?
+
+        if( const auto* re = right.m_data.opt_Infer() )
+        {
+            //DEBUG("left = " << left << ", right = " << right);
+            switch(re->ty_class)
+            {
+            case ::HIR::InferClass::None:
+            case ::HIR::InferClass::Diverge:
+                //return left.m_data.is_Generic();
+                return true;
+            case ::HIR::InferClass::Integer:
+                TU_IFLET(::HIR::TypeRef::Data, left.m_data, Primitive, le,
+                    return is_integer(le);
+                )
+                else {
+                    return left.m_data.is_Generic();
+                }
+                break;
+            case ::HIR::InferClass::Float:
+                TU_IFLET(::HIR::TypeRef::Data, left.m_data, Primitive, le,
+                    return is_float(le);
+                )
+                else {
+                    return left.m_data.is_Generic();
+                }
+                break;
+            }
+            throw "";
+        }
+
+        // A local generic could match anything, leave that up to the caller
+        if( left.m_data.is_Generic() ) {
+            DEBUG("> Generic left, success");
+            return true;
+        }
+        // A local UfcsKnown can only be becuase it couldn't be expanded earlier, assume it could match
+        if( left.m_data.is_Path() && left.m_data.as_Path().path.m_data.is_UfcsKnown() ) {
+            // True?
+            //DEBUG("> UFCS Unknown left, success");
+            return true;
+        }
+
+        // If the RHS (provided) is generic, it can only match if it binds to a local type parameter
+        if( right.m_data.is_Generic() ) {
+            // TODO: This is handled above?
+            //DEBUG("> Generic right, only if left generic");
+            return left.m_data.is_Generic();
+        }
+        // If the RHS (provided) is generic, it can only match if it binds to a local type parameter
+        if( TU_TEST1(right.m_data, Path, .binding.is_Unbound()) ) {
+            //DEBUG("> UFCS Unknown right, fuzzy");
+            return true;
+        }
+
+        if( left.m_data.tag() != right.m_data.tag() ) {
+            //DEBUG("> Tag mismatch, failure");
+            return false;
+        }
+        TU_MATCH(::HIR::TypeRef::Data, (left.m_data, right.m_data), (le, re),
+        (Infer, assert(!"infer");),
+        (Diverge, return true; ),
+        (Primitive, return le == re;),
+        (Path,
+            if( le.path.m_data.tag() != re.path.m_data.tag() )
+                return false;
+            TU_MATCH_DEF(::HIR::Path::Data, (le.path.m_data, re.path.m_data), (ple, pre),
+            (
+                return false;
+                ),
+            (Generic,
+                return matches_genericpath(params, ple, pre, ty_res, expand_generic);
+                )
+            )
+            ),
+        (Generic,
+            throw "";
+            ),
+        (TraitObject,
+            if( !matches_genericpath(params, le.m_trait.m_path, re.m_trait.m_path, ty_res, expand_generic) )
+                return false;
+            if( le.m_markers.size() != re.m_markers.size() )
+                return false;
+            for(unsigned int i = 0; i < le.m_markers.size(); i ++)
+            {
+                const auto& lm = le.m_markers[i];
+                const auto& rm = re.m_markers[i];
+                if( !matches_genericpath(params, lm, rm, ty_res, expand_generic) )
+                    return false;
+            }
+            return true;
+            ),
+        (ErasedType,
+            throw "Unexpected ErasedType in matches_type_int";
+            ),
+        (Array,
+            if( ! matches_type_int(params, *le.inner, *re.inner, ty_res, expand_generic) )
+                return false;
+            if( le.size_val != re.size_val )
+                return false;
+            return true;
+            ),
+        (Slice,
+            return matches_type_int(params, *le.inner, *re.inner, ty_res, expand_generic);
+            ),
+        (Tuple,
+            if( le.size() != re.size() )
+                return false;
+            for( unsigned int i = 0; i < le.size(); i ++ )
+                if( !matches_type_int(params, le[i], re[i], ty_res, expand_generic) )
+                    return false;
+            return true;
+            ),
+        (Borrow,
+            if( le.type != re.type )
+                return false;
+            return matches_type_int(params, *le.inner, *re.inner, ty_res, expand_generic);
+            ),
+        (Pointer,
+            if( le.type != re.type )
+                return false;
+            return matches_type_int(params, *le.inner, *re.inner, ty_res, expand_generic);
+            ),
+        (Function,
+            if( le.is_unsafe != re.is_unsafe )
+                return false;
+            if( le.m_abi != re.m_abi )
+                return false;
+            if( le.m_arg_types.size() != re.m_arg_types.size() )
+                return false;
+            for( unsigned int i = 0; i < le.m_arg_types.size(); i ++ )
+                if( !matches_type_int(params, le.m_arg_types[i], re.m_arg_types[i], ty_res, expand_generic) )
+                    return false;
+            return matches_type_int(params, *le.m_rettype, *re.m_rettype, ty_res, expand_generic);
+            ),
+        (Closure,
+            return le.node == re.node;
+            )
+        )
+        return false;
+    }
+    bool matches_genericpath(const ::HIR::GenericParams& params, const ::HIR::GenericPath& left, const ::HIR::GenericPath& right, ::HIR::t_cb_resolve_type ty_res, bool expand_generic)
+    {
+        if( left.m_path.m_crate_name != right.m_path.m_crate_name )
+            return false;
+        if( left.m_path.m_components.size() != right.m_path.m_components.size() )
+            return false;
+        for(unsigned int i = 0; i < left.m_path.m_components.size(); i ++ )
+        {
+            if( left.m_path.m_components[i] != right.m_path.m_components[i] )
+                return false;
+        }
+
+        if( left.m_params.m_types.size() > 0 || right.m_params.m_types.size() > 0 )
+        {
+            // Count mismatch. Allow due to defaults.
+            if( left.m_params.m_types.size() != right.m_params.m_types.size() ) {
+                return true;
+                //TODO(Span(), "Match generic paths " << left << " and " << right << " - count mismatch");
+            }
+            for( unsigned int i = 0; i < right.m_params.m_types.size(); i ++ )
+            {
+                if( ! matches_type_int(params, left.m_params.m_types[i], right.m_params.m_types[i], ty_res, expand_generic) )
+                    return false;
+            }
+        }
+        return true;
+    }
+}
+
+//::HIR::TypeRef HIR::Function::make_ty(const Span& sp, const ::HIR::PathParams& params) const
+//{
+//    // TODO: Obtain function type for this function (i.e. a type that is specifically for this function)
+//    auto fcn_ty_data = ::HIR::FunctionType {
+//        m_is_unsafe,
+//        m_abi,
+//        box$( monomorphise_type(sp, m_params, params,  m_return) ),
+//        {}
+//        };
+//    fcn_ty_data.m_arg_types.reserve( m_args.size() );
+//    for(const auto& arg : m_args)
+//    {
+//        fcn_ty_data.m_arg_types.push_back( monomorphise_type(sp, m_params, params,  arg.second) );
+//    }
+//    return ::HIR::TypeRef( mv$(fcn_ty_data) );
+//}
+
+namespace {
+    bool is_unbounded_infer(const ::HIR::TypeRef& type) {
+        TU_IFLET( ::HIR::TypeRef::Data, type.m_data, Infer, e,
+            return e.ty_class == ::HIR::InferClass::None || e.ty_class == ::HIR::InferClass::Diverge;
+        )
+        else {
+            return false;
+        }
+    }
+}
+
+bool ::HIR::TraitImpl::matches_type(const ::HIR::TypeRef& type, ::HIR::t_cb_resolve_type ty_res) const
+{
+    // NOTE: Don't return any impls when the type is an unbouned ivar. Wouldn't be able to pick anything anyway
+    // TODO: For `Unbound`, it could be valid, if the target is a generic.
+    // - Pure infer could also be useful (for knowing if there's any other potential impls)
+    if( is_unbounded_infer(type) || TU_TEST1(type.m_data, Path, .binding.is_Unbound()) ) {
+        return false;
+    }
+    return matches_type_int(m_params, m_type, type, ty_res, true);
+}
+bool ::HIR::TypeImpl::matches_type(const ::HIR::TypeRef& type, ::HIR::t_cb_resolve_type ty_res) const
+{
+    if( is_unbounded_infer(type) || TU_TEST1(type.m_data, Path, .binding.is_Unbound()) ) {
+        return false;
+    }
+    return matches_type_int(m_params, m_type, type, ty_res, true);
+}
+bool ::HIR::MarkerImpl::matches_type(const ::HIR::TypeRef& type, ::HIR::t_cb_resolve_type ty_res) const
+{
+    if( is_unbounded_infer(type) || TU_TEST1(type.m_data, Path, .binding.is_Unbound()) ) {
+        return false;
+    }
+    return matches_type_int(m_params, m_type, type, ty_res, true);
+}
+
+namespace {
+
+    struct TypeOrdSpecific_MixedOrdering
+    {
+    };
+
+    ::Ordering typelist_ord_specific(const Span& sp, const ::std::vector<::HIR::TypeRef>& left, const ::std::vector<::HIR::TypeRef>& right);
+
+    ::Ordering type_ord_specific(const Span& sp, const ::HIR::TypeRef& left, const ::HIR::TypeRef& right)
+    {
+        // TODO: What happens if you get `impl<T> Foo<T> for T` vs `impl<T,U> Foo<U> for T`
+
+        // A generic can't be more specific than any other type we can see
+        // - It's equally as specific as another Generic, so still false
+        if( left.m_data.is_Generic() ) {
+            return right.m_data.is_Generic() ? ::OrdEqual : ::OrdLess;
+        }
+        // - A generic is always less specific than anything but itself (handled above)
+        if( right.m_data.is_Generic() ) {
+            return ::OrdGreater;
+        }
+
+        TU_MATCH(::HIR::TypeRef::Data, (left.m_data), (le),
+        (Generic,
+            throw "";
+            ),
+        (Infer,
+            BUG(sp, "Hit infer");
+            ),
+        (Diverge,
+            BUG(sp, "Hit diverge");
+            ),
+        (Closure,
+            BUG(sp, "Hit closure");
+            ),
+        (Primitive,
+            TU_IFLET(::HIR::TypeRef::Data, right.m_data, Primitive, re,
+                if( le != re )
+                    BUG(sp, "Mismatched types - " << left << " and " << right);
+                return ::OrdEqual;
+            )
+            else {
+                BUG(sp, "Mismatched types - " << left << " and " << right);
+            }
+            ),
+        (Path,
+            if( !right.m_data.is_Path() || le.path.m_data.tag() != right.m_data.as_Path().path.m_data.tag() )
+                BUG(sp, "Mismatched types - " << left << " and " << right);
+            TU_MATCHA( (le.path.m_data, right.m_data.as_Path().path.m_data), (lpe, rpe),
+            (Generic,
+                if( lpe.m_path != rpe.m_path )
+                    BUG(sp, "Mismatched types - " << left << " and " << right);
+                return typelist_ord_specific(sp, lpe.m_params.m_types, rpe.m_params.m_types);
+                ),
+            (UfcsUnknown,
+                ),
+            (UfcsKnown,
+                ),
+            (UfcsInherent,
+                )
+            )
+            TODO(sp, "Path - " << le.path << " and " << right);
+            ),
+        (TraitObject,
+            ASSERT_BUG(sp, right.m_data.is_TraitObject(), "Mismatched types - "<< left << " vs " << right);
+            const auto& re = right.m_data.as_TraitObject();
+            ASSERT_BUG(sp, le.m_trait.m_path.m_path == re.m_trait.m_path.m_path, "Mismatched types - "<< left << " vs " << right);
+            ASSERT_BUG(sp, le.m_markers.size() == re.m_markers.size(), "Mismatched types - "<< left << " vs " << right);
+
+            auto ord = typelist_ord_specific(sp, le.m_trait.m_path.m_params.m_types, re.m_trait.m_path.m_params.m_types);
+            if( ord != ::OrdEqual )
+                return ord;
+            for(size_t i = 0; i < le.m_markers.size(); i ++)
+            {
+                ASSERT_BUG(sp, le.m_markers[i].m_path == re.m_markers[i].m_path, "Mismatched types - " << left << " vs " << right);
+                ord = typelist_ord_specific(sp, le.m_markers[i].m_params.m_types, re.m_markers[i].m_params.m_types);
+                if(ord != ::OrdEqual)
+                    return ord;
+            }
+            return ::OrdEqual;
+            ),
+        (ErasedType,
+            TODO(sp, "ErasedType - " << left);
+            ),
+        (Function,
+            TU_IFLET(::HIR::TypeRef::Data, right.m_data, Function, re,
+                TODO(sp, "Function");
+                //return typelist_ord_specific(sp, le.arg_types, re.arg_types);
+            )
+            else {
+                BUG(sp, "Mismatched types - " << left << " and " << right);
+            }
+            ),
+        (Tuple,
+            TU_IFLET(::HIR::TypeRef::Data, right.m_data, Tuple, re,
+                return typelist_ord_specific(sp, le, re);
+            )
+            else {
+                BUG(sp, "Mismatched types - " << left << " and " << right);
+            }
+            ),
+        (Slice,
+            TU_IFLET(::HIR::TypeRef::Data, right.m_data, Slice, re,
+                return type_ord_specific(sp, *le.inner, *re.inner);
+            )
+            else {
+                BUG(sp, "Mismatched types - " << left << " and " << right);
+            }
+            ),
+        (Array,
+            TU_IFLET(::HIR::TypeRef::Data, right.m_data, Array, re,
+                if( le.size_val != re.size_val )
+                    BUG(sp, "Mismatched types - " << left << " and " << right);
+                return type_ord_specific(sp, *le.inner, *re.inner);
+            )
+            else {
+                BUG(sp, "Mismatched types - " << left << " and " << right);
+            }
+            ),
+        (Pointer,
+            TU_IFLET(::HIR::TypeRef::Data, right.m_data, Pointer, re,
+                if( le.type != re.type )
+                    BUG(sp, "Mismatched types - " << left << " and " << right);
+                return type_ord_specific(sp, *le.inner, *re.inner);
+            )
+            else {
+                BUG(sp, "Mismatched types - " << left << " and " << right);
+            }
+            ),
+        (Borrow,
+            TU_IFLET(::HIR::TypeRef::Data, right.m_data, Borrow, re,
+                if( le.type != re.type )
+                    BUG(sp, "Mismatched types - " << left << " and " << right);
+                return type_ord_specific(sp, *le.inner, *re.inner);
+            )
+            else {
+                BUG(sp, "Mismatched types - " << left << " and " << right);
+            }
+            )
+        )
+        throw "Fell off end of type_ord_specific";
+    }
+
+    ::Ordering typelist_ord_specific(const Span& sp, const ::std::vector<::HIR::TypeRef>& le, const ::std::vector<::HIR::TypeRef>& re)
+    {
+        auto rv = ::OrdEqual;
+        assert(le.size() == re.size());
+        for(unsigned int i = 0; i < le.size(); i ++) {
+            auto a = type_ord_specific(sp, le[i], re[i]);
+            if( a != ::OrdEqual ) {
+                if( rv != ::OrdEqual && a != rv )
+                {
+                    DEBUG("Inconsistent ordering between type lists - i=" << i << " [" << le << "] vs [" << re << "]");
+                    throw TypeOrdSpecific_MixedOrdering {};
+                }
+                rv = a;
+            }
+        }
+        return rv;
+    }
+}
+
+namespace {
+    void add_bound_from_trait(::std::vector< ::HIR::GenericBound>& rv,  const ::HIR::TypeRef& type, const ::HIR::TraitPath& cur_trait)
+    {
+        static Span sp;
+        assert( cur_trait.m_trait_ptr );
+        const auto& tr = *cur_trait.m_trait_ptr;
+        auto monomorph_cb = monomorphise_type_get_cb(sp, &type, &cur_trait.m_path.m_params, nullptr);
+
+        for(const auto& trait_path_raw : tr.m_all_parent_traits)
+        {
+            // 1. Monomorph
+            auto trait_path_mono = monomorphise_traitpath_with(sp, trait_path_raw, monomorph_cb, false);
+            // 2. Add
+            rv.push_back( ::HIR::GenericBound::make_TraitBound({ type.clone(), mv$(trait_path_mono) }) );
+        }
+
+        // TODO: Add traits from `Self: Foo` bounds?
+        // TODO: Move associated types to the source trait.
+    }
+    ::std::vector< ::HIR::GenericBound> flatten_bounds(const ::std::vector<::HIR::GenericBound>& bounds)
+    {
+        ::std::vector< ::HIR::GenericBound >    rv;
+        for(const auto& b : bounds)
+        {
+            TU_MATCHA( (b), (be),
+            (Lifetime,
+                rv.push_back( ::HIR::GenericBound(be) );
+                ),
+            (TypeLifetime,
+                rv.push_back( ::HIR::GenericBound::make_TypeLifetime({ be.type.clone(), be.valid_for }) );
+                ),
+            (TraitBound,
+                rv.push_back( ::HIR::GenericBound::make_TraitBound({ be.type.clone(), be.trait.clone() }) );
+                add_bound_from_trait(rv,  be.type, be.trait);
+                ),
+            (TypeEquality,
+                rv.push_back( ::HIR::GenericBound::make_TypeEquality({ be.type.clone(), be.other_type.clone() }) );
+                )
+            )
+        }
+        ::std::sort(rv.begin(), rv.end(), [](const auto& a, const auto& b){ return ::ord(a,b) == OrdLess; });
+        return rv;
+    }
+}
+
+bool ::HIR::TraitImpl::more_specific_than(const ::HIR::TraitImpl& other) const
+{
+    static const Span   _sp;
+    const Span& sp = _sp;
+    TRACE_FUNCTION;
+    //DEBUG("this  = " << *this);
+    //DEBUG("other = " << other);
+
+    // >> https://github.com/rust-lang/rfcs/blob/master/text/1210-impl-specialization.md#defining-the-precedence-rules
+    // 1. If this->m_type is less specific than other.m_type: return false
+    try
+    {
+        auto ord = type_ord_specific(sp, this->m_type, other.m_type);
+        // If `*this` < `other` : false
+        if( ord != ::OrdEqual ) {
+            DEBUG("- Type " << this->m_type << " " << (ord == ::OrdLess ? "less" : "more") << " specific than " << other.m_type);
+            return ord == ::OrdGreater;
+        }
+        // 2. If any in te.impl->m_params is less specific than oe.impl->m_params: return false
+        ord = typelist_ord_specific(sp, this->m_trait_args.m_types, other.m_trait_args.m_types);
+        if( ord != ::OrdEqual ) {
+            DEBUG("- Trait arguments " << (ord == ::OrdLess ? "less" : "more") << " specific");
+            return ord == ::OrdGreater;
+        }
+    }
+    catch(const TypeOrdSpecific_MixedOrdering& e)
+    {
+        BUG(sp, "Mixed ordering in more_specific_than");
+    }
+
+    //if( other.m_params.m_bounds.size() == 0 ) {
+    //    DEBUG("- Params (none in other, some in this)");
+    //    return m_params.m_bounds.size() > 0;
+    //}
+    // 3. Compare bound set, if there is a rule in oe that is missing from te; return false
+    // TODO: Cache these lists (calculate after outer typecheck?)
+    auto bounds_t = flatten_bounds(m_params.m_bounds);
+    auto bounds_o = flatten_bounds(other.m_params.m_bounds);
+
+    DEBUG("bounds_t = " << bounds_t);
+    DEBUG("bounds_o = " << bounds_o);
+
+    // If there are less bounds in this impl, it can't be more specific.
+    if( bounds_t.size() < bounds_o.size() )
+    {
+        DEBUG("Bound count");
+        return false;
+    }
+
+    auto it_t = bounds_t.begin();
+    auto it_o = bounds_o.begin();
+    while( it_t != bounds_t.end() && it_o != bounds_o.end() )
+    {
+        auto cmp = ::ord(*it_t, *it_o);
+        if( cmp == OrdEqual )
+        {
+            ++it_t;
+            ++it_o;
+            continue ;
+        }
+
+        // If the two bounds are similar
+        if( it_t->tag() == it_o->tag() && it_t->is_TraitBound() )
+        {
+            const auto& b_t = it_t->as_TraitBound();
+            const auto& b_o = it_o->as_TraitBound();
+            // Check if the type is equal
+            if( b_t.type == b_o.type && b_t.trait.m_path.m_path == b_o.trait.m_path.m_path )
+            {
+                const auto& params_t = b_t.trait.m_path.m_params;
+                const auto& params_o = b_o.trait.m_path.m_params;
+                switch( typelist_ord_specific(sp, params_t.m_types, params_o.m_types) )
+                {
+                case ::OrdLess: return false;
+                case ::OrdGreater: return true;
+                case ::OrdEqual:    break;
+                }
+                // TODO: Find cases where there's `T: Foo<T>` and `T: Foo<U>`
+                for(unsigned int i = 0; i < params_t.m_types.size(); i ++ )
+                {
+                    if( params_t.m_types[i] != params_o.m_types[i] && params_t.m_types[i] == b_t.type )
+                    {
+                        return true;
+                    }
+                }
+                TODO(sp, *it_t << " ?= " << *it_o);
+            }
+        }
+
+        if( cmp == OrdLess )
+        {
+            ++ it_t;
+        }
+        else
+        {
+            //++ it_o;
+            return false;
+        }
+    }
+    if( it_t != bounds_t.end() )
+    {
+        return true;
+    }
+    else
+    {
+        return false;
+    }
+}
+
+// Returns `true` if the two impls overlap in the types they will accept
+bool ::HIR::TraitImpl::overlaps_with(const Crate& crate, const ::HIR::TraitImpl& other) const
+{
+    // TODO: Pre-calculate impl trees (with pointers to parent impls)
+    struct H {
+        static bool types_overlap(const ::HIR::PathParams& a, const ::HIR::PathParams& b)
+        {
+            for(unsigned int i = 0; i < ::std::min(a.m_types.size(), b.m_types.size()); i ++)
+            {
+                if( ! H::types_overlap(a.m_types[i], b.m_types[i]) )
+                    return false;
+            }
+            return true;
+        }
+        static bool types_overlap(const ::HIR::TypeRef& a, const ::HIR::TypeRef& b)
+        {
+            static Span sp;
+            //DEBUG("(" << a << "," << b << ")");
+            if( a.m_data.is_Generic() || b.m_data.is_Generic() )
+                return true;
+            // TODO: Unbound/Opaque paths?
+            if( a.m_data.tag() != b.m_data.tag() )
+                return false;
+            TU_MATCHA( (a.m_data, b.m_data), (ae, be),
+            (Generic,
+                ),
+            (Infer,
+                ),
+            (Diverge,
+                ),
+            (Closure,
+                BUG(sp, "Hit closure");
+                ),
+            (Primitive,
+                if( ae != be )
+                    return false;
+                ),
+            (Path,
+                if( ae.path.m_data.tag() != be.path.m_data.tag() )
+                    return false;
+                TU_MATCHA( (ae.path.m_data, be.path.m_data), (ape, bpe),
+                (Generic,
+                    if( ape.m_path != bpe.m_path )
+                        return false;
+                    return H::types_overlap(ape.m_params, bpe.m_params);
+                    ),
+                (UfcsUnknown,
+                    ),
+                (UfcsKnown,
+                    ),
+                (UfcsInherent,
+                    )
+                )
+                TODO(sp, "Path - " << ae.path << " and " << be.path);
+                ),
+            (TraitObject,
+                if( ae.m_trait.m_path.m_path != be.m_trait.m_path.m_path )
+                    return false;
+                if( !H::types_overlap(ae.m_trait.m_path.m_params, be.m_trait.m_path.m_params) )
+                    return false;
+                // Marker traits only overlap if the lists are the same (with overlap)
+                if( ae.m_markers.size() != be.m_markers.size() )
+                    return false;
+                for(size_t i = 0; i < ae.m_markers.size(); i++)
+                {
+                    if( ae.m_markers[i].m_path != be.m_markers[i].m_path )
+                        return false;
+                    if( !H::types_overlap(ae.m_markers[i].m_params, be.m_markers[i].m_params) )
+                        return false;
+                }
+                return true;
+                ),
+            (ErasedType,
+                TODO(sp, "ErasedType - " << a);
+                ),
+            (Function,
+                if( ae.is_unsafe != be.is_unsafe )
+                    return false;
+                if( ae.m_abi != be.m_abi )
+                    return false;
+                if( ae.m_arg_types.size() != be.m_arg_types.size() )
+                    return false;
+                for(unsigned int i = 0; i < ae.m_arg_types.size(); i ++)
+                {
+                    if( ! H::types_overlap(ae.m_arg_types[i], be.m_arg_types[i]) )
+                        return false;
+                }
+                ),
+            (Tuple,
+                if( ae.size() != be.size() )
+                    return false;
+                for(unsigned int i = 0; i < ae.size(); i ++)
+                {
+                    if( ! H::types_overlap(ae[i], be[i]) )
+                        return false;
+                }
+                ),
+            (Slice,
+                return H::types_overlap( *ae.inner, *be.inner );
+                ),
+            (Array,
+                if( ae.size_val != be.size_val )
+                    return false;
+                return H::types_overlap( *ae.inner, *be.inner );
+                ),
+            (Pointer,
+                if( ae.type != be.type )
+                    return false;
+                return H::types_overlap( *ae.inner, *be.inner );
+                ),
+            (Borrow,
+                if( ae.type != be.type )
+                    return false;
+                return H::types_overlap( *ae.inner, *be.inner );
+                )
+            )
+            return true;
+        }
+    };
+
+    // Quick Check: If the types are equal, they do overlap
+    if(this->m_type == other.m_type && this->m_trait_args == other.m_trait_args)
+    {
+        return true;
+    }
+
+    // 1. Are the impl types of the same form (or is one generic)
+    if( ! H::types_overlap(this->m_type, other.m_type) )
+        return false;
+    if( ! H::types_overlap(this->m_trait_args, other.m_trait_args) )
+        return false;
+
+    DEBUG("TODO: Handle potential overlap (when not exactly equal)");
+    //return this->m_type == other.m_type && this->m_trait_args == other.m_trait_args;
+    Span    sp;
+
+    // TODO: Use `type_ord_specific` but treat any case of mixed ordering as this returning `false`
+    try
+    {
+        type_ord_specific(sp, this->m_type, other.m_type);
+        typelist_ord_specific(sp, this->m_trait_args.m_types, other.m_trait_args.m_types);
+    }
+    catch(const TypeOrdSpecific_MixedOrdering& /*e*/)
+    {
+        return false;
+    }
+
+    // TODO: Detect `impl<T> Foo<T> for Bar<T>` vs `impl<T> Foo<&T> for Bar<T>`
+    // > Create values for impl params from the type, then check if the trait params are compatible
+    // > Requires two lists, and telling which one to use by the end
+    auto cb_ident = [](const ::HIR::TypeRef& x)->const ::HIR::TypeRef& { return x; };
+    bool is_reversed = false;
+    ::std::vector<const ::HIR::TypeRef*>    impl_tys;
+    auto cb_match = [&](unsigned int idx, const auto& /*name*/, const ::HIR::TypeRef& x)->::HIR::Compare {
+        assert(idx < impl_tys.size());
+        if( impl_tys.at(idx) )
+        {
+            DEBUG("Compare " << x << " and " << *impl_tys.at(idx));
+            return (x == *impl_tys.at(idx) ? ::HIR::Compare::Equal : ::HIR::Compare::Unequal);
+        }
+        else
+        {
+            impl_tys.at(idx) = &x;
+            return ::HIR::Compare::Equal;
+        }
+        };
+    impl_tys.resize( this->m_params.m_types.size() );
+    if( ! this->m_type.match_test_generics(sp, other.m_type, cb_ident, cb_match) )
+    {
+        DEBUG("- Type mismatch, try other ordering");
+        is_reversed = true;
+        impl_tys.clear(); impl_tys.resize( other.m_params.m_types.size() );
+        if( !other.m_type.match_test_generics(sp, this->m_type, cb_ident, cb_match) )
+        {
+            DEBUG("- Type mismatch in both orderings");
+            return false;
+        }
+        if( other.m_trait_args.match_test_generics_fuzz(sp, this->m_trait_args, cb_ident, cb_match) != ::HIR::Compare::Equal )
+        {
+            DEBUG("- Params mismatch");
+            return false;
+        }
+        // Matched with second ording
+    }
+    else if( this->m_trait_args.match_test_generics_fuzz(sp, other.m_trait_args, cb_ident, cb_match) != ::HIR::Compare::Equal )
+    {
+        DEBUG("- Param mismatch, try other ordering");
+        is_reversed = true;
+        impl_tys.clear(); impl_tys.resize( other.m_params.m_types.size() );
+        if( !other.m_type.match_test_generics(sp, this->m_type, cb_ident, cb_match) )
+        {
+            DEBUG("- Type mismatch in alt ordering");
+            return false;
+        }
+        if( other.m_trait_args.match_test_generics_fuzz(sp, this->m_trait_args, cb_ident, cb_match) != ::HIR::Compare::Equal )
+        {
+            DEBUG("- Params mismatch in alt ordering");
+            return false;
+        }
+        // Matched with second ordering
+    }
+    else
+    {
+        // Matched with first ordering
+    }
+
+    struct H2 {
+        static const ::HIR::TypeRef& monomorph(const Span& sp, const ::HIR::TypeRef& in_ty, const ::std::vector<const ::HIR::TypeRef*>& args, ::HIR::TypeRef& tmp)
+        {
+            if( ! monomorphise_type_needed(in_ty) ) {
+                return in_ty;
+            }
+            else if( const auto* tep = in_ty.m_data.opt_Generic() ) {
+                ASSERT_BUG(sp, tep->binding < args.size(), "");
+                ASSERT_BUG(sp, args[tep->binding], "");
+                return *args[tep->binding];
+            }
+            else {
+                auto monomorph_cb = [&](const auto& t)->const auto& {
+                    const auto& te = t.m_data.as_Generic();
+                    assert(te.binding < args.size());
+                    ASSERT_BUG(sp, te.binding < args.size(), "");
+                    ASSERT_BUG(sp, args[te.binding], "");
+                    return *args[te.binding];
+                    };
+                tmp = monomorphise_type_with(sp, in_ty, monomorph_cb);
+                // TODO: EAT?
+                return tmp;
+            }
+        }
+        static const ::HIR::TraitPath& monomorph(const Span& sp, const ::HIR::TraitPath& in, const ::std::vector<const ::HIR::TypeRef*>& args, ::HIR::TraitPath& tmp)
+        {
+            if( ! monomorphise_traitpath_needed(in) ) {
+                return in;
+            }
+            else {
+                auto monomorph_cb = [&](const auto& t)->const auto& {
+                    const auto& te = t.m_data.as_Generic();
+                    assert(te.binding < args.size());
+                    ASSERT_BUG(sp, te.binding < args.size(), "");
+                    ASSERT_BUG(sp, args[te.binding], "");
+                    return *args[te.binding];
+                    };
+                tmp = monomorphise_traitpath_with(sp, in, monomorph_cb, true);
+                // TODO: EAT?
+                return tmp;
+            }
+        }
+        static bool check_bounds(const ::HIR::Crate& crate, const ::HIR::TraitImpl& id, const ::std::vector<const ::HIR::TypeRef*>& args, const ::HIR::TraitImpl& g_src)
+        {
+            TRACE_FUNCTION;
+            static Span sp;
+            for(const auto& tb : id.m_params.m_bounds)
+            {
+                if(tb.is_TraitBound())
+                {
+                    ::HIR::TypeRef  tmp_ty;
+                    ::HIR::TraitPath    tmp_tp;
+                    const auto& ty = H2::monomorph(sp, tb.as_TraitBound().type, args, tmp_ty);
+                    const auto& trait = H2::monomorph(sp, tb.as_TraitBound().trait, args, tmp_tp);;
+
+                    // Determine if `ty` would be bounded (it's an ATY or generic)
+                    if( ty.m_data.is_Generic() ) {
+                        bool found = false;
+                        for(const auto& bound : g_src.m_params.m_bounds)
+                        {
+                            if(const auto* be = bound.opt_TraitBound())
+                            {
+                                if( be->type != ty ) continue;
+                                if( be->trait != trait ) continue;
+                                found = true;
+                            }
+                        }
+                        if( !found )
+                        {
+                            DEBUG("No matching bound for " << ty << " : " << trait << " in source bounds - " << g_src.m_params.fmt_bounds());
+                            return false;
+                        }
+                    }
+                    else if( TU_TEST1(ty.m_data, Path, .binding.is_Opaque()) ) {
+                        TODO(Span(), "Check bound " << ty << " : " << trait << " in source bounds or trait bounds");
+                    }
+                    else {
+                        // Search the crate for an impl
+                        bool rv = crate.find_trait_impls(trait.m_path.m_path, ty, [](const auto&t)->const auto&{ return t; }, [&](const ::HIR::TraitImpl& ti)->bool {
+                                DEBUG("impl" << ti.m_params.fmt_args() << " " << trait.m_path.m_path << ti.m_trait_args << " for " << ti.m_type << ti.m_params.fmt_bounds());
+
+                                ::std::vector<const ::HIR::TypeRef*>   impl_tys { ti.m_params.m_types.size() };
+                                auto cb_ident = [](const ::HIR::TypeRef& x)->const ::HIR::TypeRef& { return x; };
+                                auto cb_match = [&](unsigned int idx, const auto& /*name*/, const ::HIR::TypeRef& x)->::HIR::Compare {
+                                    assert(idx < impl_tys.size());
+                                    if( impl_tys.at(idx) )
+                                    {
+                                        DEBUG("Compare " << x << " and " << *impl_tys.at(idx));
+                                        return (x == *impl_tys.at(idx) ? ::HIR::Compare::Equal : ::HIR::Compare::Unequal);
+                                    }
+                                    else
+                                    {
+                                        impl_tys.at(idx) = &x;
+                                        return ::HIR::Compare::Equal;
+                                    }
+                                    };
+                                // 1. Triple-check the type matches (and get generics)
+                                if( ! ti.m_type.match_test_generics(sp, ty, cb_ident, cb_match) )
+                                    return false;
+                                // 2. Check trait params
+                                assert(trait.m_path.m_params.m_types.size() == ti.m_trait_args.m_types.size());
+                                for(size_t i = 0; i < trait.m_path.m_params.m_types.size(); i ++)
+                                {
+                                    if( !ti.m_trait_args.m_types[i].match_test_generics(sp, trait.m_path.m_params.m_types[i], cb_ident, cb_match) )
+                                        return false;
+                                }
+                                // 3. Check bounds on the impl
+                                if( !H2::check_bounds(crate, ti, impl_tys, g_src) )
+                                    return false;
+                                // 4. Check ATY bounds on the trait path
+                                for(const auto& atyb : trait.m_type_bounds)
+                                {
+                                    const auto& aty = ti.m_types.at(atyb.first);
+                                    if( !aty.data.match_test_generics(sp, atyb.second, cb_ident, cb_match) )
+                                        return false;
+                                }
+                                // All those pass? It's good.
+                                return true;
+                            });
+                        if( !rv )
+                        {
+                            return false;
+                        }
+                    }
+                }
+                else
+                {
+                    // TODO: Other bound types?
+                }
+            }
+            // No bounds failed, it's good
+            return true;
+        }
+    };
+
+    // The two impls could overlap, pending on trait bounds
+    if(is_reversed)
+    {
+        DEBUG("(reversed) impl params " << FMT_CB(os,
+                for(auto* p : impl_tys)
+                {
+                    if(p)
+                        os << *p;
+                    else
+                        os << "?";
+                    os << ",";
+                }
+                ));
+        // Check bounds on `other` using these params
+        // TODO: Take a callback that does the checks. Or somehow return a "maybe overlaps" result?
+        return H2::check_bounds(crate, other, impl_tys, *this);
+    }
+    else
+    {
+        DEBUG("impl params " << FMT_CB(os,
+                for(auto* p : impl_tys)
+                {
+                    if(p)
+                        os << *p;
+                    else
+                        os << "?";
+                    os << ",";
+                }
+                ));
+        // Check bounds on `*this`
+        return H2::check_bounds(crate, *this, impl_tys, other);
+    }
+}
+
+bool ::HIR::Crate::find_trait_impls(const ::HIR::SimplePath& trait, const ::HIR::TypeRef& type, t_cb_resolve_type ty_res, ::std::function<bool(const ::HIR::TraitImpl&)> callback) const
+{
+    auto its = this->m_trait_impls.equal_range( trait );
+    for( auto it = its.first; it != its.second; ++ it )
+    {
+        const auto& impl = it->second;
+        if( impl.matches_type(type, ty_res) ) {
+            if( callback(impl) ) {
+                return true;
+            }
+        }
+    }
+    for( const auto& ec : this->m_ext_crates )
+    {
+        if( ec.second.m_data->find_trait_impls(trait, type, ty_res, callback) ) {
+            return true;
+        }
+    }
+    return false;
+}
+bool ::HIR::Crate::find_auto_trait_impls(const ::HIR::SimplePath& trait, const ::HIR::TypeRef& type, t_cb_resolve_type ty_res, ::std::function<bool(const ::HIR::MarkerImpl&)> callback) const
+{
+    auto its = this->m_marker_impls.equal_range( trait );
+    for( auto it = its.first; it != its.second; ++ it )
+    {
+        const auto& impl = it->second;
+        if( impl.matches_type(type, ty_res) ) {
+            if( callback(impl) ) {
+                return true;
+            }
+        }
+    }
+    for( const auto& ec : this->m_ext_crates )
+    {
+        if( ec.second.m_data->find_auto_trait_impls(trait, type, ty_res, callback) ) {
+            return true;
+        }
+    }
+    return false;
+}
+bool ::HIR::Crate::find_type_impls(const ::HIR::TypeRef& type, t_cb_resolve_type ty_res, ::std::function<bool(const ::HIR::TypeImpl&)> callback) const
+{
+    // TODO: Restrict which crate is searched based on the type.
+    for( const auto& impl : this->m_type_impls )
+    {
+        if( impl.matches_type(type, ty_res) ) {
+            if( callback(impl) ) {
+                return true;
+            }
+        }
+    }
+    for( const auto& ec : this->m_ext_crates )
+    {
+        //DEBUG("- " << ec.first);
+        if( ec.second.m_data->find_type_impls(type, ty_res, callback) ) {
+            return true;
+        }
+    }
+    return false;
+}
+
+const ::MIR::Function* HIR::Crate::get_or_gen_mir(const ::HIR::ItemPath& ip, const ::HIR::ExprPtr& ep, const ::HIR::Function::args_t& args, const ::HIR::TypeRef& ret_ty) const
+{
+    if( !ep )
+    {
+        return &*ep.m_mir;
+    }
+    else
+    {
+        if( !ep.m_mir )
+        {
+            TRACE_FUNCTION_F(ip);
+            ASSERT_BUG(Span(), ep.m_state, "No ExprState for " << ip);
+
+            auto& ep_mut = const_cast<::HIR::ExprPtr&>(ep);
+
+            // Ensure typechecked
+            if( ep.m_state->stage < ::HIR::ExprState::Stage::Typecheck )
+            {
+                if( ep.m_state->stage == ::HIR::ExprState::Stage::TypecheckRequest )
+                    ERROR(Span(), E0000, "Loop in constant evaluation");
+                ep.m_state->stage = ::HIR::ExprState::Stage::TypecheckRequest;
+
+                // TODO: Set debug/timing stage
+                //Debug_SetStagePre("HIR Typecheck");
+                // - Can store that on the Expr, OR get it from the item path
+                typeck::ModuleState ms { const_cast<::HIR::Crate&>(*this) };
+                ms.m_impl_generics = ep.m_state->m_impl_generics;
+                ms.m_item_generics = ep.m_state->m_item_generics;
+                ms.m_traits = ep.m_state->m_traits;
+                Typecheck_Code(ms, const_cast<::HIR::Function::args_t&>(args), ret_ty, ep_mut);
+                //Debug_SetStagePre("Expand HIR Annotate");
+                HIR_Expand_AnnotateUsage_Expr(*this, ep_mut);
+                //Debug_SetStagePre("Expand HIR Closures");
+                HIR_Expand_Closures_Expr(*this, ep_mut);
+                //Debug_SetStagePre("Expand HIR Calls");
+                HIR_Expand_UfcsEverything_Expr(*this, ep_mut);
+                //Debug_SetStagePre("Expand HIR Reborrows");
+                HIR_Expand_Reborrows_Expr(*this, ep_mut);
+                //Debug_SetStagePre("Expand HIR ErasedType");
+                //HIR_Expand_ErasedType(*this, ep_mut);    // - Maybe?
+                //Typecheck_Expressions_Validate(*hir_crate);
+
+                ep.m_state->stage = ::HIR::ExprState::Stage::Typecheck;
+            }
+            // Generate MIR
+            if( ep.m_state->stage < ::HIR::ExprState::Stage::Mir )
+            {
+                if( ep.m_state->stage == ::HIR::ExprState::Stage::MirRequest )
+                    ERROR(Span(), E0000, "Loop in constant evaluation");
+                ep.m_state->stage = ::HIR::ExprState::Stage::MirRequest;
+                //Debug_SetStage("Lower MIR");
+                HIR_GenerateMIR_Expr(*this, ip, ep_mut, args, ret_ty);
+                ep.m_state->stage = ::HIR::ExprState::Stage::Mir;
+            }
+            assert(ep.m_mir);
+        }
+        return &*ep.m_mir;
+    }
+}