Disallow labelled branches in `defer` - fix #3960

src/check_stmt.cpp

@@ -199,6 +199,9 @@ gb_internal bool check_has_break(Ast *stmt, String const &label, bool implicit)
 		}
 		break;
 
+	case Ast_DeferStmt:
+		return check_has_break(stmt->DeferStmt.stmt, label, implicit);
+
 	case Ast_BlockStmt:
 		return check_has_break_list(stmt->BlockStmt.stmts, label, implicit);
 
@@ -2706,6 +2709,7 @@ gb_internal void check_stmt_internal(CheckerContext *ctx, Ast *node, u32 flags)
 				error(bs->label, "A branch statement's label name must be an identifier");
 				return;
 			}
+
 			Ast *ident = bs->label;
 			String name = ident->Ident.token.string;
 			Operand o = {};
@@ -2737,6 +2741,10 @@ gb_internal void check_stmt_internal(CheckerContext *ctx, Ast *node, u32 flags)
 				break;
 
 			}
+
+			if (ctx->in_defer) {
+				error(bs->label, "A labelled '%.*s' cannot be used within a 'defer'", LIT(token.string));
+			}
 		}
 
 	case_end;