MIR - Cast PhandomData fields when doing CoerceUnsized

4 files changed, 59 insertions, 8 deletions

diff --git a/src/hir_typeck/static.cpp b/src/hir_typeck/static.cpp
index b9a302a6..d1dbc42e 100644
--- a/src/hir_typeck/static.cpp
+++ b/src/hir_typeck/static.cpp
@@ -1382,3 +1382,21 @@ const ::HIR::TypeRef* StaticTraitResolve::is_type_owned_box(const ::HIR::TypeRef
     // TODO: Properly assert?
     return &pe.m_params.m_types.at(0);
 }
+const ::HIR::TypeRef* StaticTraitResolve::is_type_phantom_data(const ::HIR::TypeRef& ty) const
+{
+    if( ! ty.m_data.is_Path() ) {
+        return nullptr;
+    }
+    const auto& te = ty.m_data.as_Path();
+    
+    if( ! te.path.m_data.is_Generic() ) {
+        return nullptr;
+    }
+    const auto& pe = te.path.m_data.as_Generic();
+    
+    if( pe.m_path != m_lang_PhantomData ) {
+        return nullptr;
+    }
+    // TODO: Properly assert?
+    return &pe.m_params.m_types.at(0);
+}
diff --git a/src/hir_typeck/static.hpp b/src/hir_typeck/static.hpp
index dd35df15..1fd1d51c 100644
--- a/src/hir_typeck/static.hpp
+++ b/src/hir_typeck/static.hpp
@@ -28,6 +28,7 @@ private:
     ::HIR::SimplePath   m_lang_FnMut;
     ::HIR::SimplePath   m_lang_FnOnce;
     ::HIR::SimplePath   m_lang_Box;
+    ::HIR::SimplePath   m_lang_PhantomData;
     
 public:
     StaticTraitResolve(const ::HIR::Crate& crate):
@@ -41,6 +42,7 @@ public:
         m_lang_FnMut = m_crate.get_lang_item_path_opt("fn_mut");
         m_lang_FnOnce = m_crate.get_lang_item_path_opt("fn_once");
         m_lang_Box = m_crate.get_lang_item_path_opt("owned_box");
+        m_lang_PhantomData = m_crate.get_lang_item_path_opt("phantom_data");
         prep_indexes();
     }
 
@@ -170,5 +172,6 @@ public:
     bool type_is_sized(const Span& sp, const ::HIR::TypeRef& ty) const;
     
     const ::HIR::TypeRef* is_type_owned_box(const ::HIR::TypeRef& ty) const;
+    const ::HIR::TypeRef* is_type_phantom_data(const ::HIR::TypeRef& ty) const;
 };
 
diff --git a/src/mir/cleanup.cpp b/src/mir/cleanup.cpp
index 88096704..c2394adb 100644
--- a/src/mir/cleanup.cpp
+++ b/src/mir/cleanup.cpp
@@ -264,8 +264,16 @@ const ::HIR::Literal* MIR_Cleanup_GetConstant(const Span& sp, const StaticTraitR
                     auto ty_s = monomorphise_type_with(state.sp, se[i].ent, monomorph_cb_s, false);
                     
                     auto new_rval = MIR_Cleanup_CoerceUnsized(state, mutator, ty_d, ty_s,  ::MIR::LValue::make_Field({ box$(value.clone()), i }));
-                    auto new_lval = mutator.new_temporary( mv$(ty_d) );
-                    mutator.push_statement( ::MIR::Statement::make_Assign({ new_lval.clone(), mv$(new_rval) }) );
+                    auto new_lval = mutator.in_temporary( mv$(ty_d), mv$(new_rval) );
+                    
+                    ents.push_back( mv$(new_lval) );
+                }
+                else if( state.m_resolve.is_type_phantom_data( se[i].ent ) )
+                {
+                    auto ty_d = monomorphise_type_with(state.sp, se[i].ent, monomorph_cb_d, false);
+                    
+                    auto new_rval = ::MIR::RValue::make_Cast({ ::MIR::LValue::make_Field({ box$(value.clone()), i }), ty_d.clone() });
+                    auto new_lval = mutator.in_temporary( mv$(ty_d), mv$(new_rval) );
                     
                     ents.push_back( mv$(new_lval) );
                 }
@@ -279,7 +287,8 @@ const ::HIR::Literal* MIR_Cleanup_GetConstant(const Span& sp, const StaticTraitR
             ents.reserve( se.size() );
             for(unsigned int i = 0; i < se.size(); i++)
             {
-                if( i == str.m_markings.coerce_unsized_index ) {
+                if( i == str.m_markings.coerce_unsized_index )
+                {
                     auto ty_d = monomorphise_type_with(state.sp, se[i].second.ent, monomorph_cb_d, false);
                     auto ty_s = monomorphise_type_with(state.sp, se[i].second.ent, monomorph_cb_s, false);
                     
@@ -289,7 +298,17 @@ const ::HIR::Literal* MIR_Cleanup_GetConstant(const Span& sp, const StaticTraitR
                     
                     ents.push_back( mv$(new_lval) );
                 }
-                else {
+                else if( state.m_resolve.is_type_phantom_data( se[i].second.ent ) )
+                {
+                    auto ty_d = monomorphise_type_with(state.sp, se[i].second.ent, monomorph_cb_d, false);
+                    
+                    auto new_rval = ::MIR::RValue::make_Cast({ ::MIR::LValue::make_Field({ box$(value.clone()), i }), ty_d.clone() });
+                    auto new_lval = mutator.in_temporary( mv$(ty_d), mv$(new_rval) );
+                    
+                    ents.push_back( mv$(new_lval) );
+                }
+                else
+                {
                     ents.push_back( ::MIR::LValue::make_Field({ box$(value.clone()), i}) );
                 }
             }
@@ -439,6 +458,12 @@ void MIR_Cleanup(const StaticTraitResolve& resolve, const ::HIR::ItemPath& path,
                         // (&-ptr being destination is otherwise invalid)
                         // TODO Share with the CoerceUnsized handling?
                     )
+                    // Casts to PhantomData are only valid from PhandomData, and are added by _CoerceUnsized
+                    else if( state.m_resolve.is_type_phantom_data(e.type) )
+                    {
+                        // Leave 
+                        MIR_ASSERT(state, state.m_resolve.is_type_phantom_data(src_ty) != nullptr, "PhandomData can only cast from PhantomData");
+                    }
                     // - CoerceUnsized should re-create the inner type if known.
                     else TU_IFLET( ::HIR::TypeRef::Data, e.type.m_data, Path, te,
                         TU_IFLET( ::HIR::TypeRef::Data, src_ty.m_data, Path, ste,
diff --git a/src/trans/codegen_c.cpp b/src/trans/codegen_c.cpp
index 37c96a83..1a0ba042 100644
--- a/src/trans/codegen_c.cpp
+++ b/src/trans/codegen_c.cpp
@@ -425,6 +425,11 @@ namespace {
                             }
                             ),
                         (Cast,
+                            if( m_resolve.is_type_phantom_data(ve.type) ) {
+                                m_of << "/* PhandomData cast */\n";
+                                continue ;
+                            }
+                            
                             emit_lvalue(e.dst);
                             m_of << " = ";
                             m_of << "("; emit_ctype(ve.type); m_of << ")";
@@ -758,10 +763,10 @@ namespace {
                 m_of << " " << inner;
                 ),
             (Path,
-                if( const auto* ity = m_resolve.is_type_owned_box(ty) ) {
-                    emit_ctype_ptr(*ity, inner);
-                    return ;
-                }
+                //if( const auto* ity = m_resolve.is_type_owned_box(ty) ) {
+                //    emit_ctype_ptr(*ity, inner);
+                //    return ;
+                //}
                 TU_MATCHA( (te.binding), (tpb),
                 (Struct,
                     m_of << "struct s_" << Trans_Mangle(te.path);