[COMMITTED 01/32] gccrs: Evaluate the enum's discriminant in a const context

[arthur . cohen]

From: Ryutaro Okada <1015ry...@gmail.com>

gcc/rust/ChangeLog:

        * backend/rust-compile-resolve-path.cc: Evaluate the enum's 
discriminant in a const context

gcc/testsuite/ChangeLog:

        * rust/compile/enum_discriminant1.rs: New test.

Signed-off-by: Ryutaro Okada <1015ry...@gmail.com>
---
 gcc/rust/backend/rust-compile-resolve-path.cc    | 2 ++
 gcc/testsuite/rust/compile/enum_discriminant1.rs | 7 +++++++
 2 files changed, 9 insertions(+)
 create mode 100644 gcc/testsuite/rust/compile/enum_discriminant1.rs

diff --git a/gcc/rust/backend/rust-compile-resolve-path.cc 
b/gcc/rust/backend/rust-compile-resolve-path.cc
index 115dd046465..3cb1eb6faa5 100644
--- a/gcc/rust/backend/rust-compile-resolve-path.cc
+++ b/gcc/rust/backend/rust-compile-resolve-path.cc
@@ -105,7 +105,9 @@ ResolvePathRef::attempt_constructor_expression_lookup (
 
   // make the ctor for the union
   HIR::Expr &discrim_expr = variant->get_discriminant ();
+  ctx->push_const_context ();
   tree discrim_expr_node = CompileExpr::Compile (discrim_expr, ctx);
+  ctx->pop_const_context ();
   tree folded_discrim_expr = fold_expr (discrim_expr_node);
   tree qualifier = folded_discrim_expr;
 
diff --git a/gcc/testsuite/rust/compile/enum_discriminant1.rs 
b/gcc/testsuite/rust/compile/enum_discriminant1.rs
new file mode 100644
index 00000000000..32092b2c2a5
--- /dev/null
+++ b/gcc/testsuite/rust/compile/enum_discriminant1.rs
@@ -0,0 +1,7 @@
+enum Foo {
+    Bar = 3 + 12,
+}
+
+fn test() -> Foo { // { dg-warning "function is never used" }
+    return Foo::Bar;
+}
\ No newline at end of file
-- 
2.49.0