Fix ICE with continue/break/return in while condition,Fixes #3977

Author: Harishankar14

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

@@ -1537,24 +1537,44 @@ TypeCheckExpr::visit (HIR::LoopExpr &expr)
 				      : TyTy::TupleType::get_unit_type ();
 }
 
-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 *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 ());
+void TypeCheckExpr::visit(HIR::WhileLoopExpr &expr) {
+  context->push_new_while_loop_context(expr.get_mappings().get_hirid());
+  TyTy::BaseType *predicate_type =
+      TypeCheckExpr::Resolve(expr.get_predicate_expr());
+  if (predicate_type->get_kind() == TyTy::TypeKind::ERROR) {
+      infered = TyTy::TupleType::get_unit_type();
+      context->pop_loop_context();
       return;
-    }
-
-  context->pop_loop_context ();
-  infered = TyTy::TupleType::get_unit_type ();
+  }
+  if (predicate_type->get_kind() == TyTy::TypeKind::NEVER) {
+      rust_error_at(expr.get_predicate_expr().get_locus(),
+                    "expected boolean expression in %<while%> condition");
+      infered = TyTy::TupleType::get_unit_type();
+      context->pop_loop_context();
+      return;
+  }
+  if (predicate_type->get_kind() != TyTy::TypeKind::BOOL) {
+      rust_error_at(expr.get_predicate_expr().get_locus(),
+                    "expected boolean expression in %<while%> condition");
+      infered = TyTy::TupleType::get_unit_type();
+      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());
+      infered = TyTy::TupleType::get_unit_type();
+      context->pop_loop_context();
+      return;
+  }
+  if (block_expr->get_kind() == TyTy::TypeKind::ERROR) {
+      infered = TyTy::TupleType::get_unit_type();
+      context->pop_loop_context();
+      return;
+  }
+  context->pop_loop_context();
+  infered = TyTy::TupleType::get_unit_type();
 }
 
 void

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

@@ -0,0 +1,72 @@
+// Test for issue #3977: ICE in fold_convert_loc with diverging expressions in while conditions
+// { dg-excess-errors "expected boolean expression" }
+
+fn test_continue() {
+    loop {
+        while continue {} // { dg-error "expected boolean expression in 'while' condition" }
+    }
+}
+
+fn test_break() {
+    loop {
+        while break {} // { dg-error "expected boolean expression in 'while' condition" }
+    }
+}
+
+fn test_return() {
+    while return {} // { dg-error "expected boolean expression in 'while' condition" }
+}
+
+fn test_return_with_value() {
+    while return 42 {} // { dg-error "expected boolean expression in 'while' condition" }
+}
+
+fn test_infinite_loop() {
+    while loop {} {} // { dg-error "expected boolean expression in 'while' condition" }
+}
+
+fn test_nested_continue() {
+    loop {
+        loop {
+            while continue {} // { dg-error "expected boolean expression in 'while' condition" }
+        }
+    }
+}
+
+fn test_labeled_break() {
+    'outer: loop {
+        while break 'outer {} // { dg-error "expected boolean expression in 'while' condition" }
+    }
+}
+
+fn test_labeled_continue() {
+    'outer: loop {
+        while continue 'outer {} // { dg-error "expected boolean expression in 'while' condition" }
+    }
+}
+
+// Valid cases that should NOT error
+fn test_valid_boolean() {
+    while true {}
+    while false {}
+}
+
+fn test_valid_expression() {
+    let x = 5;
+    while x > 0 {}
+}
+
+fn test_valid_function_call() -> bool {
+    fn condition() -> bool { true }
+    while condition() {}
+    true
+}
+
+fn main() {
+    test_valid_boolean();
+    test_valid_expression();
+    test_valid_function_call();
+    
+    // The error cases would cause compilation to fail
+    // so they're tested separately
+}