gccrs:fix ICE with continue/break/return in while condition

gcc/rust/backend/rust-compile-expr.cc

@@ -803,7 +803,18 @@ CompileExpr::visit (HIR::WhileLoopExpr &expr)
   ctx->add_statement (loop_begin_label_decl);
   ctx->push_loop_begin_label (loop_begin_label);
 
-  tree condition = CompileExpr::Compile (expr.get_predicate_expr (), ctx);
+  HIR::Expr &predicate = expr.get_predicate_expr ();
+  TyTy::BaseType *predicate_type = nullptr;
+  bool ok
+    = ctx->get_tyctx ()->lookup_type (predicate.get_mappings ().get_hirid (),
+				      &predicate_type);
+  rust_assert (ok && predicate_type != nullptr);
+  tree condition = CompileExpr::Compile (predicate, ctx);
+  if (predicate_type->get_kind () == TyTy::TypeKind::NEVER)
+    {
+      ctx->add_statement (condition);
+      condition = boolean_true_node;
+    }
   tree exit_condition = fold_build1_loc (expr.get_locus (), TRUTH_NOT_EXPR,
 					 boolean_type_node, condition);
   tree exit_expr = Backend::exit_expression (exit_condition, expr.get_locus ());

gcc/rust/typecheck/rust-hir-type-check-expr.cc

@@ -1541,18 +1541,25 @@ void
 TypeCheckExpr::visit (HIR::WhileLoopExpr &expr)
 {
   context->push_new_while_loop_context (expr.get_mappings ().get_hirid ());
-
-  TypeCheckExpr::Resolve (expr.get_predicate_expr ());
+  TyTy::BaseType *predicate_type
+    = TypeCheckExpr::Resolve (expr.get_predicate_expr ());
+  if (predicate_type->get_kind () != TyTy::TypeKind::BOOL
+      && predicate_type->get_kind () != TyTy::TypeKind::NEVER)
+    {
+      rust_error_at (expr.get_predicate_expr ().get_locus (),
+		     "expected boolean expression in %<while%> condition");
+      context->pop_loop_context ();
+      return;
+    }
   TyTy::BaseType *block_expr = TypeCheckExpr::Resolve (expr.get_loop_block ());
-
   if (!block_expr->is_unit ())
     {
       rust_error_at (expr.get_loop_block ().get_locus (),
 		     "expected %<()%> got %s",
 		     block_expr->as_string ().c_str ());
+      context->pop_loop_context ();
       return;
     }
-
   context->pop_loop_context ();
   infered = TyTy::TupleType::get_unit_type ();
 }
@@ -1602,7 +1609,6 @@ TypeCheckExpr::visit (HIR::ContinueExpr &expr)
 		     "%<continue%> outside of a loop");
       return;
     }
-
   infered = new TyTy::NeverType (expr.get_mappings ().get_hirid ());
 }
 

gcc/testsuite/rust/compile/issue-3977.rs

@@ -0,0 +1,65 @@
+// Test for issue #3977 - ICE with continue/break/return in while condition
+
+fn diverge() -> ! {
+    loop {}
+}
+
+fn test_continue() {
+    loop {
+        while continue {}
+    }
+}
+
+fn test_break() {      
+    loop {
+        while break {}
+    }
+}
+
+fn test_return() {
+    loop {
+        while return {}
+    }
+}
+
+fn test_labeled_break() {
+    'outer: loop {
+        loop {
+            while break 'outer {}
+        }
+    }
+}
+
+fn test_labeled_continue() {
+    'outer: loop {
+        loop {
+            while continue 'outer {}
+        }
+    }
+}
+
+fn test_complex_if_else() {
+    loop {
+        while if true { continue } else { break } {}
+    }
+}
+
+fn foo() {
+    while diverge() {
+        break
+    }
+    let _x = 5;
+}
+
+fn main() {
+    // Just reference them so they're "used"
+    if false {
+        test_continue();
+        test_break();
+        test_return();
+        test_labeled_break();
+        test_labeled_continue();
+        test_complex_if_else();
+        foo();
+    }
+}