gccrs: Fix ICE when compiling path which resolves to trait constant

Fixes Rust-GCC#3552

gcc/rust/ChangeLog:

	* backend/rust-compile-resolve-path.cc (HIRCompileBase::query_compile): check for Expr trait
	* hir/rust-hir-dump.cc (Dump::visit): expr is optional

gcc/testsuite/ChangeLog:

	* rust/compile/issue-3552.rs: New test.

Signed-off-by: Philip Herron <herron.philip@googlemail.com>

1 files changed, 21 insertions, 0 deletions

diff --git a/gcc/rust/backend/rust-compile-resolve-path.cc b/gcc/rust/backend/rust-compile-resolve-path.cc
index 9423951..d4901a4 100644
--- a/gcc/rust/backend/rust-compile-resolve-path.cc
+++ b/gcc/rust/backend/rust-compile-resolve-path.cc
@@ -301,6 +301,27 @@ HIRCompileBase::query_compile (HirId ref, TyTy::BaseType *lookup,
 	    trait->get_mappings ().get_defid (), &trait_ref);
 	  rust_assert (ok);
 
+	  if (trait_item.value ()->get_item_kind ()
+	      == HIR::TraitItem::TraitItemKind::CONST)
+	    {
+	      auto &c
+		= *static_cast<HIR::TraitItemConst *> (trait_item.value ());
+	      if (!c.has_expr ())
+		{
+		  rich_location r (line_table, expr_locus);
+		  r.add_range (trait->get_locus ());
+		  r.add_range (c.get_locus ());
+		  rust_error_at (r, "no default expression on trait constant");
+		  return error_mark_node;
+		}
+
+	      return CompileExpr::Compile (c.get_expr (), ctx);
+	    }
+
+	  if (trait_item.value ()->get_item_kind ()
+	      != HIR::TraitItem::TraitItemKind::FUNC)
+	    return error_mark_node;
+
 	  // the type resolver can only resolve type bounds to their trait
 	  // item so its up to us to figure out if this path should resolve
 	  // to an trait-impl-block-item or if it can be defaulted to the