checker: check s.$method(arg) argument is []string (#8455)

vlib/v/checker/checker.v

@@ -3699,7 +3699,21 @@ fn (mut c Checker) comptime_call(mut node ast.ComptimeCall) table.Type {
 		node.result_type = rtyp
 		return rtyp
 	}
-	if node.is_vweb || node.method_name == 'method' {
+	if node.method_name == 'method' {
+		if node.args_var.len > 0 {
+			v := node.scope.find_var(node.args_var) or {
+				c.error('unknown identifier `$node.args_var`', node.method_pos)
+				return table.void_type
+			}
+			s := c.table.type_to_str(c.expr(v.expr))
+			if s != '[]string' {
+				c.error('expected `[]string`, not s', node.method_pos)
+			}
+		}
+		// assume string for now
+		return table.string_type
+	}
+	if node.is_vweb {
 		return table.string_type
 	}
 	// s.$my_str()

vlib/v/checker/tests/comptime_call_method.out

@@ -0,0 +1,14 @@
+vlib/v/checker/tests/comptime_call_method.vv:10:7: error: unknown identifier `wrong`
+    8 |     s1 := S1{}
+    9 |     $for method in S1.methods {
+   10 |         s1.$method(wrong)
+      |             ~~~~~~
+   11 |         arg := 7
+   12 |         s1.$method(arg)
+vlib/v/checker/tests/comptime_call_method.vv:12:7: error: expected `[]string`, not s
+   10 |         s1.$method(wrong)
+   11 |         arg := 7
+   12 |         s1.$method(arg)
+      |             ~~~~~~
+   13 |     }
+   14 | }

vlib/v/checker/tests/comptime_call_method.vv

@@ -0,0 +1,14 @@
+struct S1 {}
+
+fn (t S1) m(s string) int {
+	return 7
+}
+
+fn test_methods_arg() {
+	s1 := S1{}
+	$for method in S1.methods {
+		s1.$method(wrong)
+		arg := 7
+		s1.$method(arg)
+	}
+}

vlib/v/parser/comptime.v

@@ -269,6 +269,7 @@ fn (mut p Parser) comptime_selector(left ast.Expr) ast.Expr {
 		mut args_var := ''
 		if p.tok.kind == .name {
 			args_var = p.tok.lit
+			p.mark_var_as_used(args_var)
 			p.next()
 		}
 		p.check(.rpar)

vlib/v/tests/comptime_call_test.v

@@ -31,7 +31,6 @@ fn test_for_methods() {
 	$for method in Test.methods {
 		// currently the checker thinks all $method calls return string
 		$if method.return_type is string {
-			//~ $if method.name == 's' {println('yes')}
 			v := test.$method()
 			r += v.str()
 		}
@@ -50,3 +49,19 @@ fn test_for_methods() {
 	}
 	assert r == '?testTwo'
 }
+
+struct S1 {}
+
+fn (t S1) rep(s string, i int) string {
+	return s.repeat(i)
+}
+
+fn test_methods_arg() {
+	s1 := S1{}
+	$for method in S1.methods {
+		arr := ['!', '3']
+		r := s1.$method(arr)
+		assert r == '!!!'
+	}
+}
+