Using [] or .foo on $$ functions would not raise error but instead crash #2919.

releasenotes.md

@@ -29,6 +29,7 @@
 - Update to dstring.append_string to take any type converting to String.
 - Flag `--cpu-flags` doesn't work if the first item is an exclusion. #2905
 - Reallocating overaligned memory with the LibcAllocator was unsafe.
+- Using [] or .foo on $$ functions would not raise error but instead crash
 
 ## 0.7.9 Change list
 

src/compiler/sema_expr.c

@@ -4198,7 +4198,10 @@ DEFAULT:
 	}
 
 	if (!sema_expr_check_assign(context, expr, NULL)) return false;
-
+	if (subscripted->expr_kind == EXPR_BUILTIN)
+	{
+		RETURN_SEMA_ERROR(expr, "Builtins cannot be subscripted.");
+	}
 	Expr *index = exprptr(expr->subscript_expr.index.expr);
 
 	// 3. Check failability due to value.
@@ -4295,7 +4298,10 @@ static inline bool sema_expr_analyse_subscript(SemaContext *context, Expr *expr,
 	// Evaluate the expression to index.
 	Expr *subscripted = exprptr(expr->subscript_expr.expr);
 	if (!sema_analyse_expr(context, subscripted)) return false;
-
+	if (subscripted->expr_kind == EXPR_BUILTIN)
+	{
+		RETURN_SEMA_ERROR(expr, "Builtins cannot be subscripted.");
+	}
 	// 3. Check failability due to value.
 	bool optional = IS_OPTIONAL(subscripted);
 
@@ -4752,6 +4758,10 @@ static inline bool sema_expr_analyse_slice(SemaContext *context, Expr *expr)
 	ASSERT_SPAN(expr, expr->expr_kind == EXPR_SLICE);
 	Expr *subscripted = exprptr(expr->slice_expr.expr);
 	if (!sema_analyse_expr(context, subscripted)) return false;
+	if (subscripted->expr_kind == EXPR_BUILTIN)
+	{
+		RETURN_SEMA_ERROR(expr, "A builtin cannot be sliced.");
+	}
 	bool optional = IS_OPTIONAL(subscripted);
 	Type *type = type_flatten(subscripted->type);
 	Type *original_type = type_no_optional(subscripted->type);

test/test_suite/builtins/builtin_props.c3

@@ -0,0 +1,5 @@
+fn int main()
+{
+	if ($$veccompne.type == int.typeid) // #error:  A builtin has no support for properties
+	return 0;
+}

test/test_suite/builtins/builtin_subscript.c3

@@ -0,0 +1,13 @@
+fn void main()
+{
+	$$veccompgt[1]; // #error: Builtins cannot be subscripted.
+}
+fn void test()
+{
+	$$veccompeq[1] = 33; // #error: Builtins cannot be subscripted.
+}
+
+fn void test2()
+{
+	$$veccomple[..] = 52; // #error: A builtin cannot be sliced.
+}