gccrs: Fix ICE when compiling block expressions in array capacity

We need to reuse the existing compile_constant_item helper which handles
the case if this is a simple expression, fn-call or a block expression.
The patch extracts out this helper as a static method so this can be used
in more places.

Fixes Rust-GCC#3566

gcc/rust/ChangeLog:

	* backend/rust-compile-base.cc (HIRCompileBase::address_expression): new helper constexpr
	* backend/rust-compile-base.h: prototype
	* backend/rust-compile-type.cc (TyTyResolveCompile::visit): call constexpr helper

gcc/testsuite/ChangeLog:

	* rust/compile/issue-3566-1.rs: New test.
	* rust/compile/issue-3566-2.rs: New test.

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

1 files changed, 6 insertions, 0 deletions

diff --git a/gcc/rust/backend/rust-compile-base.h b/gcc/rust/backend/rust-compile-base.h
index 3c50535..4d55407 100644
--- a/gcc/rust/backend/rust-compile-base.h
+++ b/gcc/rust/backend/rust-compile-base.h
@@ -31,6 +31,12 @@ public:
 
   static tree address_expression (tree expr, location_t locus);
 
+  static tree compile_constant_expr (
+    Context *ctx, HirId coercion_id, TyTy::BaseType *resolved_type,
+    TyTy::BaseType *expected_type,
+    const Resolver::CanonicalPath &canonical_path, HIR::Expr &const_value_expr,
+    location_t locus, location_t expr_locus);
+
 protected:
   HIRCompileBase (Context *ctx) : ctx (ctx) {}