Allow for `foo() or_else unreachable()` and other diverging procedures

1 files changed, 23 insertions, 3 deletions

diff --git a/src/check_expr.cpp b/src/check_expr.cpp
index cf9f2f751..96adde013 100644
--- a/src/check_expr.cpp
+++ b/src/check_expr.cpp
@@ -119,6 +119,7 @@ void check_or_else_split_types(CheckerContext *c, Operand *x, String const &name
 void check_or_else_expr_no_value_error(CheckerContext *c, String const &name, Operand const &x, Type *type_hint);
 void check_or_return_split_types(CheckerContext *c, Operand *x, String const &name, Type **left_type_, Type **right_type_);
 
+bool is_diverging_expr(Ast *expr);
 
 void check_did_you_mean_print(DidYouMeanAnswers *d, char const *prefix = "") {
 	auto results = did_you_mean_results(d);
@@ -7399,8 +7400,25 @@ ExprKind check_or_else_expr(CheckerContext *c, Operand *o, Ast *node, Type *type
 		return Expr_Expr;
 	}
 
-	check_multi_expr_with_type_hint(c, &y, default_value, x.type);
-	error_operand_no_value(&y);
+	bool y_is_diverging = false;
+	check_expr_base(c, &y, default_value, x.type);
+	switch (y.mode) {
+	case Addressing_NoValue:
+		if (is_diverging_expr(y.expr)) {
+			// Allow
+			y.mode = Addressing_Value;
+			y_is_diverging = true;
+		} else {
+			error_operand_no_value(&y);
+			y.mode = Addressing_Invalid;
+		}
+		break;
+	case Addressing_Type:
+		error_operand_not_expression(&y);
+		y.mode = Addressing_Invalid;
+		break;
+	}
+
 	if (y.mode == Addressing_Invalid) {
 		o->mode = Addressing_Value;
 		o->type = t_invalid;
@@ -7414,7 +7432,9 @@ ExprKind check_or_else_expr(CheckerContext *c, Operand *o, Ast *node, Type *type
 	add_type_and_value(&c->checker->info, arg, x.mode, x.type, x.value);
 
 	if (left_type != nullptr) {
-		check_assignment(c, &y, left_type, name);
+		if (!y_is_diverging) {
+			check_assignment(c, &y, left_type, name);
+		}
 	} else {
 		check_or_else_expr_no_value_error(c, name, x, type_hint);
 	}