- x'1234' +++ (ichar[1]) { 'A' } would fail due to missing const folding.

releasenotes.md

@@ -42,6 +42,7 @@
 - Assert when encountering a malformed module alias.
 - Assert when encountering a test function with raw vaarg parameters.
 - `foo.x` was not always handled correctly when `foo` was optional.
+- `x'1234' +++ (ichar[1]) { 'A' }` would fail due to missing const folding.
 
 ### Stdlib changes
 - Add `ThreadPool` join function to wait for all threads to finish in the pool without destroying the threads.

src/compiler/sema_const.c

@@ -187,6 +187,10 @@ static bool sema_concat_bytes_and_other(SemaContext *context, Expr *expr, Expr *
 		case CONST_SLICE:
 		case CONST_INITIALIZER:
 			if (!cast_implicit(context, right, type_get_inferred_array(indexed), false)) return false;
+			if (!sema_cast_const(right))
+			{
+				RETURN_SEMA_ERROR(right, "Could not concatenate with the right hand side.");
+			}
 			expr_contract_array(&right->const_expr, left->const_expr.const_kind);
 			goto RETRY;
 	}

test/test_suite/compile_time/concat_convert.c3

@@ -0,0 +1,5 @@
+fn int main()
+{
+	const A = x'1234' +++ (ichar[1]) { 'A' };
+	return 0;
+}