Add support for constants within blocks

BlockExpr's can contain constants these are Items which can exist within
the BlockExpr Stmt list. Items like structs, functions and constants all
inherit from Item so there is some duplication of code but we still
do not support the forward declared Items within a stmt list so the
duplication will need to be fixed as part of that bug.

Fixes #711

5 files changed, 98 insertions, 0 deletions

diff --git a/gcc/rust/backend/rust-compile-stmt.h b/gcc/rust/backend/rust-compile-stmt.h
index 1a2f02c..21e5814 100644
--- a/gcc/rust/backend/rust-compile-stmt.h
+++ b/gcc/rust/backend/rust-compile-stmt.h
@@ -48,6 +48,33 @@ public:
     translated = CompileExpr::Compile (stmt.get_expr (), ctx);
   }
 
+  void visit (HIR::ConstantItem &constant) override
+  {
+    TyTy::BaseType *resolved_type = nullptr;
+    bool ok
+      = ctx->get_tyctx ()->lookup_type (constant.get_mappings ().get_hirid (),
+					&resolved_type);
+    rust_assert (ok);
+
+    ::Btype *type = TyTyResolveCompile::compile (ctx, resolved_type);
+    Bexpression *value = CompileExpr::Compile (constant.get_expr (), ctx);
+
+    const Resolver::CanonicalPath *canonical_path = nullptr;
+    rust_assert (ctx->get_mappings ()->lookup_canonical_path (
+      constant.get_mappings ().get_crate_num (),
+      constant.get_mappings ().get_nodeid (), &canonical_path));
+
+    std::string ident = canonical_path->get ();
+    Bexpression *const_expr
+      = ctx->get_backend ()->named_constant_expression (type, ident, value,
+							constant.get_locus ());
+
+    ctx->push_const (const_expr);
+    ctx->insert_const_decl (constant.get_mappings ().get_hirid (), const_expr);
+
+    translated = const_expr;
+  }
+
   void visit (HIR::LetStmt &stmt) override
   {
     // nothing to do
diff --git a/gcc/rust/hir/rust-ast-lower-stmt.h b/gcc/rust/hir/rust-ast-lower-stmt.h
index 50ccc9f..eab0922 100644
--- a/gcc/rust/hir/rust-ast-lower-stmt.h
+++ b/gcc/rust/hir/rust-ast-lower-stmt.h
@@ -83,6 +83,34 @@ public:
     mappings->insert_hir_stmt (crate_num, mapping.get_hirid (), translated);
   }
 
+  void visit (AST::ConstantItem &constant) override
+  {
+    HIR::Visibility vis = HIR::Visibility::create_public ();
+
+    HIR::Type *type = ASTLoweringType::translate (constant.get_type ().get ());
+    HIR::Expr *expr = ASTLoweringExpr::translate (constant.get_expr ().get ());
+
+    auto crate_num = mappings->get_current_crate ();
+    Analysis::NodeMapping mapping (crate_num, constant.get_node_id (),
+				   mappings->get_next_hir_id (crate_num),
+				   mappings->get_next_localdef_id (crate_num));
+
+    HIR::ConstantItem *constant_item
+      = new HIR::ConstantItem (mapping, constant.get_identifier (), vis,
+			       std::unique_ptr<HIR::Type> (type),
+			       std::unique_ptr<HIR::Expr> (expr),
+			       constant.get_outer_attrs (),
+			       constant.get_locus ());
+    translated = constant_item;
+
+    mappings->insert_hir_item (mapping.get_crate_num (), mapping.get_hirid (),
+			       constant_item);
+    mappings->insert_hir_stmt (mapping.get_crate_num (), mapping.get_hirid (),
+			       constant_item);
+    mappings->insert_location (crate_num, mapping.get_hirid (),
+			       constant.get_locus ());
+  }
+
   void visit (AST::LetStmt &stmt) override
   {
     HIR::Pattern *variables
diff --git a/gcc/rust/resolve/rust-ast-resolve-stmt.h b/gcc/rust/resolve/rust-ast-resolve-stmt.h
index 3a0904e..98fcaf2 100644
--- a/gcc/rust/resolve/rust-ast-resolve-stmt.h
+++ b/gcc/rust/resolve/rust-ast-resolve-stmt.h
@@ -51,6 +51,30 @@ public:
     ResolveExpr::go (stmt.get_expr ().get (), stmt.get_node_id ());
   }
 
+  void visit (AST::ConstantItem &constant) override
+  {
+    auto path = ResolveConstantItemToCanonicalPath::resolve (constant);
+    resolver->get_name_scope ().insert (
+      path, constant.get_node_id (), constant.get_locus (), false,
+      [&] (const CanonicalPath &, NodeId, Location locus) -> void {
+	RichLocation r (constant.get_locus ());
+	r.add_range (locus);
+	rust_error_at (r, "redefined multiple times");
+      });
+    resolver->insert_new_definition (constant.get_node_id (),
+				     Definition{constant.get_node_id (),
+						constant.get_node_id ()});
+
+    ResolveType::go (constant.get_type ().get (), constant.get_node_id ());
+    ResolveExpr::go (constant.get_expr ().get (), constant.get_node_id ());
+
+    // the mutability checker needs to verify for immutable decls the number
+    // of assignments are <1. This marks an implicit assignment
+    resolver->mark_decl_mutability (constant.get_node_id (), false);
+    resolver->mark_assignment_to_decl (constant.get_node_id (),
+				       constant.get_node_id ());
+  }
+
   void visit (AST::LetStmt &stmt) override
   {
     if (stmt.has_init_expr ())
diff --git a/gcc/rust/typecheck/rust-hir-type-check-stmt.h b/gcc/rust/typecheck/rust-hir-type-check-stmt.h
index 17def2b..74bc037 100644
--- a/gcc/rust/typecheck/rust-hir-type-check-stmt.h
+++ b/gcc/rust/typecheck/rust-hir-type-check-stmt.h
@@ -55,6 +55,19 @@ public:
       = TyTy::TupleType::get_unit_type (stmt.get_mappings ().get_hirid ());
   }
 
+  void visit (HIR::ConstantItem &constant) override
+  {
+    TyTy::BaseType *type = TypeCheckType::Resolve (constant.get_type ());
+    TyTy::BaseType *expr_type
+      = TypeCheckExpr::Resolve (constant.get_expr (), false);
+
+    infered = type->unify (expr_type);
+    context->insert_type (constant.get_mappings (), infered);
+
+    // notify the constant folder of this
+    ConstFold::ConstFoldItem::fold (constant);
+  }
+
   void visit (HIR::LetStmt &stmt) override
   {
     infered = new TyTy::TupleType (stmt.get_mappings ().get_hirid ());
diff --git a/gcc/testsuite/rust/compile/torture/constant2.rs b/gcc/testsuite/rust/compile/torture/constant2.rs
new file mode 100644
index 0000000..d06324e
--- /dev/null
+++ b/gcc/testsuite/rust/compile/torture/constant2.rs
@@ -0,0 +1,6 @@
+fn main() {
+    const C: usize = 42;
+
+    let _a = C;
+    let _b: [i32; C] = [0; C];
+}