checker: check argument count for C fn with attribute (vlang#8728)

Author: ntrel

vlib/v/checker/checker.v

@@ -1909,10 +1909,11 @@ pub fn (mut c Checker) call_fn(mut call_expr ast.CallExpr) table.Type {
 	if f.language != .v || call_expr.language != .v {
 		// ignore C function of type `fn()`, assume untyped
 		// For now don't check C functions that are variadic, underscored, capitalized
-		// or have no params and return int
+		// or have no params or attributes and return int
 		if f.language == .c && f.params.len != call_expr.args.len && !f.is_variadic
-			&& f.name[2] != `_` && !f.name[2].is_capital()
-			&& (f.params.len != 0 || f.return_type !in [table.void_type, table.int_type]) {
+			&& f.name[2] != `_` && !f.name[2].is_capital() && (f.params.len != 0
+			|| f.return_type !in [table.void_type, table.int_type]
+			|| f.attrs.len > 0) {
 			// change to error later
 			c.warn('expected $f.params.len arguments, but got $call_expr.args.len', call_expr.pos)
 		}

vlib/v/checker/tests/c_fn_surplus_args.out

@@ -24,4 +24,12 @@ vlib/v/checker/tests/c_fn_surplus_args.vv:13:2: error: the `main` function canno
    12 |     // avoid cgen whilst warning, later above should error
    13 |     main()
       |     ~~~~~~
-   14 | }
+   14 |     C.af() // ok
+   15 |     C.af(3)
+vlib/v/checker/tests/c_fn_surplus_args.vv:15:4: error: expected 0 arguments, but got 1
+   13 |     main()
+   14 |     C.af() // ok
+   15 |     C.af(3)
+      |       ~~~~~
+   16 | }
+   17 |

vlib/v/checker/tests/c_fn_surplus_args.vv

@@ -11,4 +11,9 @@ fn main() {
 	C.ret(1)
 	// avoid cgen whilst warning, later above should error
 	main()
+	C.af() // ok
+	C.af(3)
 }
+
+[trusted]
+fn C.af()int