[COMMITTED 32/43] gccrs: Fix missing error diag on const parser and crash in typecheck

[arthur.cohen@opensrcsec.com]

From: Philip Herron <herron.philip@googlemail.com>

We need to force braces on the default expression in the parser but also
the typecheck cant const eval when the typecheck fails otherwise it will
crash because invalid error mark node.

Fixes Rust-GCC/gccrs#4173

gcc/rust/ChangeLog:

	* parse/rust-parse-impl.hxx:
	* typecheck/rust-hir-type-check-base.cc:

gcc/testsuite/ChangeLog:

	* rust/compile/issue-4173-1.rs: New test.
	* rust/compile/issue-4173-2.rs: New test.
	* rust/compile/issue-4173-3.rs: New test.

Signed-off-by: Philip Herron <herron.philip@googlemail.com>
---
 gcc/rust/parse/rust-parse-impl.hxx             | 10 ++++++++++
 gcc/rust/typecheck/rust-hir-type-check-base.cc |  4 ++++
 gcc/testsuite/rust/compile/issue-4173-1.rs     |  8 ++++++++
 gcc/testsuite/rust/compile/issue-4173-2.rs     |  9 +++++++++
 gcc/testsuite/rust/compile/issue-4173-3.rs     |  9 +++++++++
 5 files changed, 40 insertions(+)
 create mode 100644 gcc/testsuite/rust/compile/issue-4173-1.rs
 create mode 100644 gcc/testsuite/rust/compile/issue-4173-2.rs
 create mode 100644 gcc/testsuite/rust/compile/issue-4173-3.rs

diff --git a/gcc/rust/parse/rust-parse-impl.hxx b/gcc/rust/parse/rust-parse-impl.hxx
index 9d7d529d4ee..49a5a45b9f4 100644
--- a/gcc/rust/parse/rust-parse-impl.hxx
+++ b/gcc/rust/parse/rust-parse-impl.hxx
@@ -2021,6 +2021,16 @@ Parser<ManagedTokenSource>::parse_generic_param (EndTokenPred is_end_token)
 	    if (default_expr.value ().get_kind ()
 		== AST::GenericArg::Kind::Either)
 	      default_expr = default_expr.value ().disambiguate_to_const ();
+	    else if (default_expr.value ().get_kind ()
+		     != AST::GenericArg::Kind::Const)
+	      {
+		Error error (
+		  default_expr.value ().get_locus (),
+		  "expressions must be enclosed in braces to be used as const "
+		  "generic arguments");
+		add_error (std::move (error));
+		default_expr = tl::nullopt;
+	      }
 	  }
 
 	param = std::unique_ptr<AST::ConstGenericParam> (
diff --git a/gcc/rust/typecheck/rust-hir-type-check-base.cc b/gcc/rust/typecheck/rust-hir-type-check-base.cc
index 4c276ce83d0..399b9594609 100644
--- a/gcc/rust/typecheck/rust-hir-type-check-base.cc
+++ b/gcc/rust/typecheck/rust-hir-type-check-base.cc
@@ -683,6 +683,10 @@ TypeCheckBase::resolve_generic_params (
 		auto expr_type
 		  = TypeCheckExpr::Resolve (param.get_default_expression ());
 
+		if (specified_type->is<TyTy::ErrorType> ()
+		    || expr_type->is<TyTy::ErrorType> ())
+		  break;
+
 		coercion_site (param.get_mappings ().get_hirid (),
 			       TyTy::TyWithLocation (specified_type),
 			       TyTy::TyWithLocation (
diff --git a/gcc/testsuite/rust/compile/issue-4173-1.rs b/gcc/testsuite/rust/compile/issue-4173-1.rs
new file mode 100644
index 00000000000..f5ec82bbc70
--- /dev/null
+++ b/gcc/testsuite/rust/compile/issue-4173-1.rs
@@ -0,0 +1,8 @@
+#![feature(no_core)]
+#![no_core]
+#![feature(lang_items)]
+
+#[lang = "sized"]
+trait Sized {}
+
+pub struct S<const N: u32 = { 1 }>;
diff --git a/gcc/testsuite/rust/compile/issue-4173-2.rs b/gcc/testsuite/rust/compile/issue-4173-2.rs
new file mode 100644
index 00000000000..d6e26bb54c6
--- /dev/null
+++ b/gcc/testsuite/rust/compile/issue-4173-2.rs
@@ -0,0 +1,9 @@
+#![feature(no_core)]
+#![no_core]
+#![feature(lang_items)]
+
+#[lang = "sized"]
+trait Sized {}
+
+pub struct S<const N: u32 = { u32::MAX }>;
+// { dg-error "failed to resolve path segment using an impl Probe" "" { target *-*-* } .-1 }
diff --git a/gcc/testsuite/rust/compile/issue-4173-3.rs b/gcc/testsuite/rust/compile/issue-4173-3.rs
new file mode 100644
index 00000000000..c4933c4ff97
--- /dev/null
+++ b/gcc/testsuite/rust/compile/issue-4173-3.rs
@@ -0,0 +1,9 @@
+#![feature(no_core)]
+#![no_core]
+#![feature(lang_items)]
+
+#[lang = "sized"]
+trait Sized {}
+
+pub struct S<const N: u32 = u32::MAX>;
+// { dg-error "expressions must be enclosed in braces to be used as const generic arguments" "" { target *-*-* } .-1 }
-- 
2.50.1