Merge #601

601: union support for hir type checking and gcc backend r=dkm a=dkm

From Mark Wielaard : https://gcc.gnu.org/pipermail/gcc-rust/2021-August/000107.html

> 
> Treat a union as a Struct variant like a tuple struct.  Add an
> iterator and get_identifier functions to the AST Union class.  Same
> for the HIR Union class, plus a get_generics_params method. Add a new
> ADTKind enum and adt_kind field to the ADTType to select the
> underlying abstract data type (struct struct, tuple struct or union,
> with enum as possible future variant).
> 
> An union constructor can have only one field. Add an union_index field
> to StructExprStruct which is set during type checking in the
> TypeCheckStructExpr HIR StructExprStructFields visitor.
> 
> For the Gcc_backend class rename fill_in_struct to fill_in_fields and
> use it from a new union_type method. Handle union_index in
> constructor_expression (so only one field is initialized).

Fixes #157 

Co-authored-by: Mark Wielaard <mark@klomp.org>

1 files changed, 32 insertions, 0 deletions

diff --git a/gcc/rust/resolve/rust-ast-resolve-stmt.h b/gcc/rust/resolve/rust-ast-resolve-stmt.h
index 210a9fc..b604432 100644
--- a/gcc/rust/resolve/rust-ast-resolve-stmt.h
+++ b/gcc/rust/resolve/rust-ast-resolve-stmt.h
@@ -131,6 +131,38 @@ public:
     resolver->get_type_scope ().pop ();
   }
 
+  void visit (AST::Union &union_decl) override
+  {
+    auto path = CanonicalPath::new_seg (union_decl.get_node_id (),
+					union_decl.get_identifier ());
+    resolver->get_type_scope ().insert (
+      path, union_decl.get_node_id (), union_decl.get_locus (), false,
+      [&] (const CanonicalPath &, NodeId, Location locus) -> void {
+	RichLocation r (union_decl.get_locus ());
+	r.add_range (locus);
+	rust_error_at (r, "redefined multiple times");
+      });
+
+    NodeId scope_node_id = union_decl.get_node_id ();
+    resolver->get_type_scope ().push (scope_node_id);
+
+    if (union_decl.has_generics ())
+      {
+	for (auto &generic : union_decl.get_generic_params ())
+	  {
+	    ResolveGenericParam::go (generic.get (), union_decl.get_node_id ());
+	  }
+      }
+
+    union_decl.iterate ([&] (AST::StructField &field) mutable -> bool {
+      ResolveType::go (field.get_field_type ().get (),
+		       union_decl.get_node_id ());
+      return true;
+    });
+
+    resolver->get_type_scope ().pop ();
+  }
+
   void visit (AST::Function &function) override
   {
     auto path = ResolveFunctionItemToCanonicalPath::resolve (function);