Allow omitting = true for designated initializers of bitstruct bools.

resources/grammar/grammar.y

@@ -441,6 +441,7 @@ param_path
 
 arg
 	: param_path '=' expr
+	| param_path
 	| type
 	| param_path '=' type
 	| expr

src/compiler/expr.c

@@ -211,6 +211,7 @@ bool expr_is_constant_eval(Expr *expr, ConstantEvalKind eval_kind)
 			return expr_list_is_constant_eval(expr->cond_expr, eval_kind);
 		case EXPR_DESIGNATOR:
 			expr = expr->designator_expr.value;
+			if (!expr) return true;
 			goto RETRY;
 		case EXPR_EXPR_BLOCK:
 		case EXPR_DECL:

src/compiler/parse_expr.c

@@ -465,7 +465,7 @@ Expr *parse_vasplat(ParseContext *c)
 /**
  * param_list ::= ('...' arg | arg (',' arg)*)?
  *
- * parameter ::= (param_path '=')? expr
+ * parameter ::= ((param_path '=')? expr) | param_path
  */
 bool parse_arg_list(ParseContext *c, Expr ***result, TokenType param_end, bool *splat, bool vasplat)
 {
@@ -483,11 +483,9 @@ bool parse_arg_list(ParseContext *c, Expr ***result, TokenType param_end, bool *
 			expr = expr_new(EXPR_DESIGNATOR, start_span);
 			expr->designator_expr.path = path;
 
-			// Expect the '=' after.
-			CONSUME_OR_RET(TOKEN_EQ, false);
-
-			// Now parse the rest
-			ASSIGN_EXPR_OR_RET(expr->designator_expr.value, parse_expr(c), false);
+			if (try_consume(c, TOKEN_EQ)) {
+				ASSIGN_EXPR_OR_RET(expr->designator_expr.value, parse_expr(c), false);
+			}
 
 			RANGE_EXTEND_PREV(expr);
 		}

src/compiler/sema_expr.c

@@ -1331,6 +1331,10 @@ INLINE bool sema_call_expand_arguments(SemaContext *context, CalledDecl *callee,
 			}
 
 			// 8g. Set the parameter
+			if (!arg->designator_expr.value)
+			{
+				RETURN_SEMA_ERROR(arg, "Expected a value for this argument.");
+			}
 			actual_args[index] = arg->designator_expr.value;
 			continue;
 		}

src/compiler/sema_initializers.c

@@ -406,15 +406,24 @@ static bool sema_expr_analyse_designated_initializer(SemaContext *context, Type
 	bool optional = false;
 	Type *inner_type = NULL;
 	bool is_inferred = type_is_inferred(flattened);
+	int bitmember_count_without_value = 0;
 	VECEACH(init_expressions, i)
 	{
 		Expr *expr = init_expressions[i];
 		Decl *member;
 		Type *result = sema_expr_analyse_designator(context, original, expr, &max_index, &member);
 		if (!result) return false;
+		bool is_bitmember = member && member->decl_kind == DECL_VAR && member->var.kind == VARDECL_BITMEMBER;
 		Expr *value = expr->designator_expr.value;
+		if (!value && is_bitmember && member->var.start_bit == member->var.end_bit && type_flatten(result) == type_bool) {
+			assert(is_bitstruct);
+			value = expr_new_const_bool(INVALID_SPAN, type_bool, true);
+			expr->designator_expr.value = value;
+			bitmember_count_without_value += 1;
+		}
+		if (!value) RETURN_SEMA_ERROR(expr, "This initializer needs a value.");
 		if (!sema_analyse_expr_rhs(context, result, value, true, NULL)) return false;
-		if (member && member->decl_kind == DECL_VAR && member->var.kind == VARDECL_BITMEMBER)
+		if (is_bitmember)
 		{
 			if (!sema_bit_assignment_check(context, value, member)) return false;
 		}
@@ -426,6 +435,9 @@ static bool sema_expr_analyse_designated_initializer(SemaContext *context, Type
 			continue;
 		}
 	}
+	if (bitmember_count_without_value != 0 && bitmember_count_without_value != vec_size(init_expressions)) {
+		RETURN_SEMA_ERROR(initializer, "Mixing the omission of initializers is not permitted.");
+	}
 	Type *type;
 	if (!is_structlike && is_inferred)
 	{
@@ -522,6 +534,7 @@ static void sema_create_const_initializer_from_designated_init(ConstInitializer
 		Expr *expr = init_expressions[i];
 		DesignatorElement **path = expr->designator_expr.path;
 		Expr *value = expr->designator_expr.value;
+		assert(value);
 		sema_update_const_initializer_with_designator(const_init, path, path + vec_size(path), value);
 	}
 }

test/test_suite/bitstruct/bitstruct_init.c3

@@ -59,4 +59,46 @@ fn void test2()
 fn void test3()
 {
     Foo abc = { .x = -4, .z = 0, .y = 8 }; // #error: would be truncated
-}
+}
+
+bitstruct Flags1 : int
+{
+    bool a;
+    bool b;
+    bool c;
+}
+
+distinct Bool = bool;
+
+bitstruct Flags2 : int
+{
+    bool a : 0;
+    Bool b : 1;
+    int  c : 2..3;
+    bool d : 6;
+}
+
+struct Flags2_Struct
+{
+    bool a;
+    bool b;
+    int c;
+    bool d;
+}
+
+fn void test4()
+{
+    Flags1 flags1 = {.a, .b, .c};
+    flags1 = {.a};
+    flags1 = {.a = true, .b = true, .c = false};
+    flags1 = {.a, .b = true, .c = true}; // #error: Mixing the omission
+    Foo foo = { .x = 0, .z }; // #error: needs a value
+
+    Flags2 flags2 = {.b, .d};
+    flags2 = {.b, .c, .d}; // #error: needs a value
+    flags2 = {.a, .c = 1, .d}; // #error: Mixing the omission
+
+    Flags2_Struct flags2s;
+    flags2s = {.b, .c, .d}; // #error: needs a value
+    flags2s = {.a, .c = 1, .d}; // #error: needs a value
+}