MIR - Remove Deref from inputs to RValue::DstMeta/DstPtr

7 files changed, 94 insertions, 25 deletions

diff --git a/src/mir/check.cpp b/src/mir/check.cpp
index 382694a7..ad8c9613 100644
--- a/src/mir/check.cpp
+++ b/src/mir/check.cpp
@@ -542,13 +542,65 @@ void MIR_Validate(const StaticTraitResolve& resolve, const ::HIR::ItemPath& path
                         // TODO: Check return type
                         ),
                     (DstMeta,
-                        // TODO: Ensure that the input type is a: Generic, Array, or DST
-                        MIR_ASSERT(state, e.val.is_Deref(), "DstMeta requires a deref as input");
+                        ::HIR::TypeRef  tmp;
+                        const auto& ty = state.get_lvalue_type(tmp, e.val);
+                        const ::HIR::TypeRef*   ity_p = nullptr;
+                        if( (ity_p = state.is_type_owned_box(ty)) )
+                            ;
+                        else if( ty.m_data.is_Borrow() )
+                            ity_p = &*ty.m_data.as_Borrow().inner;
+                        else if( ty.m_data.is_Pointer() )
+                            ity_p = &*ty.m_data.as_Pointer().inner;
+                        else
+                            MIR_BUG(state, "DstMeta requires a &-ptr as input, got " << ty);
+                        const auto& ity = *ity_p;
+                        if( ity.m_data.is_Generic() )
+                            ;
+                        else if( ity.m_data.is_Path() && ity.m_data.as_Path().binding.is_Opaque() )
+                            ;
+                        else if( ity.m_data.is_Array() )
+                            ;
+                        else if( ity.m_data.is_Slice() )
+                            ;
+                        else if( ity.m_data.is_TraitObject() )
+                            ;
+                        else if( ity.m_data.is_Path() )
+                        {
+                            // TODO: Check DST type of this path
+                        }
+                        else
+                        {
+                            MIR_BUG(state, "DstMeta on invalid type - " << ty);
+                        }
                         // TODO: Check return type
                         ),
                     (DstPtr,
-                        // TODO: Ensure that the input type is a DST
-                        MIR_ASSERT(state, e.val.is_Deref(), "DstPtr requires a deref as input");
+                        ::HIR::TypeRef  tmp;
+                        const auto& ty = state.get_lvalue_type(tmp, e.val);
+                        const ::HIR::TypeRef*   ity_p = nullptr;
+                        if( (ity_p = state.is_type_owned_box(ty)) )
+                            ;
+                        else if( ty.m_data.is_Borrow() )
+                            ity_p = &*ty.m_data.as_Borrow().inner;
+                        else if( ty.m_data.is_Pointer() )
+                            ity_p = &*ty.m_data.as_Pointer().inner;
+                        else
+                            MIR_BUG(state, "DstPtr requires a &-ptr as input, got " << ty);
+                        const auto& ity = *ity_p;
+                        if( ity.m_data.is_Slice() )
+                            ;
+                        else if( ity.m_data.is_TraitObject() )
+                            ;
+                        else if( ity.m_data.is_Path() && ity.m_data.as_Path().binding.is_Opaque() )
+                            ;
+                        else if( ity.m_data.is_Path() )
+                        {
+                            // TODO: Check DST type of this path
+                        }
+                        else
+                        {
+                            MIR_BUG(state, "DstPtr on invalid type - " << ty);
+                        }
                         // TODO: Check return type
                         ),
                     (MakeDst,
diff --git a/src/mir/cleanup.cpp b/src/mir/cleanup.cpp
index 3dc7f418..8056ae27 100644
--- a/src/mir/cleanup.cpp
+++ b/src/mir/cleanup.cpp
@@ -418,7 +418,7 @@ const ::HIR::Literal* MIR_Cleanup_GetConstant(const Span& sp, const StaticTraitR
     // Allocate a temporary for the vtable pointer itself
     auto vtable_lv = mutator.new_temporary( mv$(vtable_ty) );
     // - Load the vtable and store it
-    auto vtable_rval = ::MIR::RValue::make_DstMeta({ ::MIR::LValue::make_Deref({ box$(receiver_lvp.clone()) }) });
+    auto vtable_rval = ::MIR::RValue::make_DstMeta({ receiver_lvp.clone() });
     mutator.push_statement( ::MIR::Statement::make_Assign({ vtable_lv.clone(), mv$(vtable_rval) }) );
 
     auto fcn_lval = ::MIR::LValue::make_Field({ box$(::MIR::LValue::make_Deref({ box$(vtable_lv) })), vtable_idx });
@@ -478,7 +478,7 @@ const ::HIR::Literal* MIR_Cleanup_GetConstant(const Span& sp, const StaticTraitR
                 {
                     return mutator.in_temporary(
                         ::HIR::TypeRef::new_pointer(::HIR::BorrowType::Shared, ::HIR::TypeRef::new_unit()),
-                        ::MIR::RValue::make_DstPtr({ ::MIR::LValue::make_Deref({ box$(lv) }) })
+                        ::MIR::RValue::make_DstPtr({ mv$(lv) })
                         );
                 }
                 else
@@ -492,7 +492,7 @@ const ::HIR::Literal* MIR_Cleanup_GetConstant(const Span& sp, const StaticTraitR
     }
     else
     {
-        auto ptr_rval = ::MIR::RValue::make_DstPtr({ ::MIR::LValue::make_Deref({ box$(receiver_lvp.clone()) }) });
+        auto ptr_rval = ::MIR::RValue::make_DstPtr({ receiver_lvp.clone() });
 
         auto ptr_lv = mutator.new_temporary( ::HIR::TypeRef::new_pointer(::HIR::BorrowType::Shared, ::HIR::TypeRef::new_unit()) );
         mutator.push_statement( ::MIR::Statement::make_Assign({ ptr_lv.clone(), mv$(ptr_rval) }) );
@@ -618,8 +618,7 @@ bool MIR_Cleanup_Unsize_GetMetadata(const ::MIR::TypeResolve& state, MirMutator&
             if( src_ty.m_data.is_TraitObject() )
             {
                 out_src_is_dst = true;
-                auto deref_ptr_val = ::MIR::LValue::make_Deref({ box$(ptr_value.clone()) });
-                out_meta_val = ::MIR::RValue::make_DstMeta({ mv$(deref_ptr_val) });
+                out_meta_val = ::MIR::RValue::make_DstMeta({ ptr_value.clone() });
             }
             else
             {
@@ -648,8 +647,7 @@ bool MIR_Cleanup_Unsize_GetMetadata(const ::MIR::TypeResolve& state, MirMutator&
         if( source_is_dst )
         {
             auto ty_unit_ptr = ::HIR::TypeRef::new_pointer(::HIR::BorrowType::Shared, ::HIR::TypeRef::new_unit());
-            auto deref_ptr_val = ::MIR::LValue::make_Deref({ box$(ptr_value) });
-            auto thin_ptr_lval = mutator.in_temporary( mv$(ty_unit_ptr), ::MIR::RValue::make_DstPtr({ mv$(deref_ptr_val) }) );
+            auto thin_ptr_lval = mutator.in_temporary( mv$(ty_unit_ptr), ::MIR::RValue::make_DstPtr({ mv$(ptr_value) }) );
 
             return ::MIR::RValue::make_MakeDst({ mv$(thin_ptr_lval), mv$(meta_lval) });
         }
@@ -913,10 +911,16 @@ void MIR_Cleanup(const StaticTraitResolve& resolve, const ::HIR::ItemPath& path,
                     MIR_Cleanup_LValue(state, mutator,  re.val);
                     ),
                 (DstMeta,
-                    MIR_Cleanup_LValue(state, mutator,  re.val);
+                    // HACK: Ensure that the box Deref conversion fires here.
+                    auto v = ::MIR::LValue::make_Deref({ box$(re.val) });
+                    MIR_Cleanup_LValue(state, mutator,  v);
+                    re.val = mv$( *v.as_Deref().val );
                     ),
                 (DstPtr,
-                    MIR_Cleanup_LValue(state, mutator,  re.val);
+                    // HACK: Ensure that the box Deref conversion fires here.
+                    auto v = ::MIR::LValue::make_Deref({ box$(re.val) });
+                    MIR_Cleanup_LValue(state, mutator,  v);
+                    re.val = mv$( *v.as_Deref().val );
                     ),
                 (MakeDst,
                     MIR_Cleanup_LValue(state, mutator,  re.ptr_val);
diff --git a/src/mir/from_hir.cpp b/src/mir/from_hir.cpp
index e130f60e..6eb91386 100644
--- a/src/mir/from_hir.cpp
+++ b/src/mir/from_hir.cpp
@@ -320,7 +320,7 @@ namespace {
                     ::MIR::LValue   len_lval;
                     if( e.extra_bind.is_valid() || e.trailing.size() > 0 )
                     {
-                        len_lval = m_builder.lvalue_or_temp(sp, ::HIR::CoreType::Usize, ::MIR::RValue::make_DstMeta({ lval.clone() }));
+                        len_lval = m_builder.lvalue_or_temp(sp, ::HIR::CoreType::Usize, ::MIR::RValue::make_DstMeta({ m_builder.get_ptr_to_dst(sp, lval).clone() }));
                     }
 
                     for(unsigned int i = 0; i < e.leading.size(); i ++)
@@ -1181,7 +1181,7 @@ namespace {
                     {
                         // HACK: FixedSizeArray uses `A: Unsize<[T]>` which will lead to the above code not working (as the size isn't known).
                         // - Maybe _Meta on the `&A` would work as a stopgap (since A: Sized, it won't collide with &[T] or similar)
-                        auto size_lval = m_builder.lvalue_or_temp( node.span(), ::HIR::TypeRef(::HIR::CoreType::Usize), ::MIR::RValue::make_DstMeta({ ::MIR::LValue::make_Deref({ box$(ptr_lval.clone()) }) }) );
+                        auto size_lval = m_builder.lvalue_or_temp( node.span(), ::HIR::TypeRef(::HIR::CoreType::Usize), ::MIR::RValue::make_DstMeta({ ptr_lval.clone() }) );
                         m_builder.set_result( node.span(), ::MIR::RValue::make_MakeDst({ mv$(ptr_lval), mv$(size_lval) }) );
                     }
                     else
@@ -1227,9 +1227,7 @@ namespace {
                 limit_val = ::MIR::Constant( e.size_val );
                 ),
             (Slice,
-                // TODO: What if this is of an unsized field? Later checks require that the inner be a LValue::Deref
-                //ASSERT_BUG(node.span(), value.is_Deref(), "Slice index not via a deref");
-                limit_val = ::MIR::RValue::make_DstMeta({ value.clone() });
+                limit_val = ::MIR::RValue::make_DstMeta({ m_builder.get_ptr_to_dst(node.m_value->span(), value).clone() });
                 )
             )
 
diff --git a/src/mir/from_hir.hpp b/src/mir/from_hir.hpp
index dc11232e..b644e66f 100644
--- a/src/mir/from_hir.hpp
+++ b/src/mir/from_hir.hpp
@@ -226,6 +226,9 @@ private:
 public:
     void with_val_type(const Span& sp, const ::MIR::LValue& val, ::std::function<void(const ::HIR::TypeRef&)> cb) const;
     bool lvalue_is_copy(const Span& sp, const ::MIR::LValue& lv) const;
+
+    // Obtain the base fat poiner for a dst reference. Errors if it wasn't via a fat pointer
+    const ::MIR::LValue& get_ptr_to_dst(const Span& sp, const ::MIR::LValue& lv) const;
 };
 
 class MirConverter:
diff --git a/src/mir/from_hir_match.cpp b/src/mir/from_hir_match.cpp
index 008bef0c..3940a1c1 100644
--- a/src/mir/from_hir_match.cpp
+++ b/src/mir/from_hir_match.cpp
@@ -1775,7 +1775,7 @@ int MIR_LowerHIR_Match_Simple__GeneratePattern(MirBuilder& builder, const Span&
 
                 // Compare length
                 auto test_lval = builder.lvalue_or_temp(sp, ::HIR::CoreType::Usize, ::MIR::RValue( ::MIR::Constant::make_Uint(re.len) ));
-                auto len_val = builder.lvalue_or_temp(sp, ::HIR::CoreType::Usize, ::MIR::RValue::make_DstMeta({ val.clone() }));
+                auto len_val = builder.lvalue_or_temp(sp, ::HIR::CoreType::Usize, ::MIR::RValue::make_DstMeta({ builder.get_ptr_to_dst(sp, val).clone() }));
                 auto cmp_lval = builder.lvalue_or_temp(sp, ::HIR::CoreType::Bool, ::MIR::RValue::make_BinOp({ mv$(len_val), ::MIR::eBinOp::EQ, mv$(test_lval) }));
 
                 auto len_succ_bb = builder.new_bb_unlinked();
@@ -1794,7 +1794,7 @@ int MIR_LowerHIR_Match_Simple__GeneratePattern(MirBuilder& builder, const Span&
 
                 // Compare length
                 auto test_lval = builder.lvalue_or_temp(sp, ::HIR::CoreType::Usize, ::MIR::RValue( ::MIR::Constant::make_Uint(re.min_len) ));
-                auto len_val = builder.lvalue_or_temp(sp, ::HIR::CoreType::Usize, ::MIR::RValue::make_DstMeta({ val.clone() }));
+                auto len_val = builder.lvalue_or_temp(sp, ::HIR::CoreType::Usize, ::MIR::RValue::make_DstMeta({ builder.get_ptr_to_dst(sp, val).clone() }));
                 auto cmp_lval = builder.lvalue_or_temp(sp, ::HIR::CoreType::Bool, ::MIR::RValue::make_BinOp({ mv$(len_val), ::MIR::eBinOp::LT, mv$(test_lval) }));
 
                 auto len_succ_bb = builder.new_bb_unlinked();
@@ -3677,7 +3677,7 @@ void DecisionTreeGen::generate_branches_Slice(
         ERROR(sp, E0000, "Non-exhaustive match over " << ty);
     }
 
-    auto val_len = m_builder.lvalue_or_temp(sp, ::HIR::CoreType::Usize, ::MIR::RValue::make_DstMeta({ val.clone() }));
+    auto val_len = m_builder.lvalue_or_temp(sp, ::HIR::CoreType::Usize, ::MIR::RValue::make_DstMeta({ m_builder.get_ptr_to_dst(sp, val).clone() }));
 
     // NOTE: Un-deref the slice
     ASSERT_BUG(sp, val.is_Deref(), "slice matches must be passed a deref");
diff --git a/src/mir/mir_builder.cpp b/src/mir/mir_builder.cpp
index 6df64a0e..530ee0e9 100644
--- a/src/mir/mir_builder.cpp
+++ b/src/mir/mir_builder.cpp
@@ -1419,6 +1419,20 @@ void MirBuilder::moved_lvalue(const Span& sp, const ::MIR::LValue& lv)
     )
 }
 
+const ::MIR::LValue& MirBuilder::get_ptr_to_dst(const Span& sp, const ::MIR::LValue& lv) const
+{
+    // Undo field accesses
+    const auto* lvp = &lv;
+    while(lvp->is_Field())
+        lvp = &*lvp->as_Field().val;
+
+    // TODO: Enum variants?
+
+    ASSERT_BUG(sp, lvp->is_Deref(), "Access of an unsized field without a dereference - " << lv);
+
+    return *lvp->as_Deref().val;
+}
+
 // --------------------------------------------------------------------
 
 ScopeHandle::~ScopeHandle()
diff --git a/src/trans/codegen_c.cpp b/src/trans/codegen_c.cpp
index a376721d..83e2ab8a 100644
--- a/src/trans/codegen_c.cpp
+++ b/src/trans/codegen_c.cpp
@@ -1267,15 +1267,13 @@ namespace {
                         (DstMeta,
                             emit_lvalue(e.dst);
                             m_of << " = ";
-                            MIR_ASSERT(mir_res, ve.val.is_Deref(), "DstMeta on non-deref");
-                            emit_lvalue(*ve.val.as_Deref().val);
+                            emit_lvalue(ve.val);
                             m_of << ".META";
                             ),
                         (DstPtr,
                             emit_lvalue(e.dst);
                             m_of << " = ";
-                            MIR_ASSERT(mir_res, ve.val.is_Deref(), "DstPtr on non-deref");
-                            emit_lvalue(*ve.val.as_Deref().val);
+                            emit_lvalue(ve.val);
                             m_of << ".PTR";
                             ),
                         (MakeDst,