cgen: fix compile time reflection for method types (.typ was always 0) (#16310)

vlib/v/gen/c/comptime.v

@@ -512,20 +512,23 @@ fn (mut g Gen) comptime_for(node ast.ComptimeFor) {
 				}
 				g.writeln('}));\n')
 			}
-			mut sig := 'anon_fn_'
+			mut sig := 'fn ('
 			// skip the first (receiver) arg
 			for j, arg in method.params[1..] {
 				// TODO: ignore mut/pts in sig for now
 				typ := arg.typ.set_nr_muls(0)
-				sig += '$typ'
+				sig += g.table.sym(typ).name
 				if j < method.params.len - 2 {
-					sig += '_'
+					sig += ', '
 				}
 			}
-			sig += '_$method.return_type'
+			sig += ')'
+			ret_type := g.table.sym(method.return_type).name
+			if ret_type != 'void' {
+				sig += ' $ret_type'
+			}
 			styp := g.table.find_type_idx(sig)
-			// println(styp)
+
-			// if styp == 0 { }
 			// TODO: type aliases
 			ret_typ := method.return_type.idx()
 			g.writeln('\t${node.val_var}.typ = $styp;')

vlib/v/tests/comptime_for_test.v

@@ -48,18 +48,29 @@ fn test_comptime_for() {
 
 fn test_comptime_for_with_if() {
 	println(@FN)
+	mut methods_found := map[string]int{}
 	$for method in App.methods {
 		println('  method: ' + no_lines('$method'))
 		$if method.typ is fn () {
+			methods_found['fn()'] += 1
 			assert method.name in ['run', 'method2']
 		}
+		$if method.typ is fn () int {
+			methods_found['fn() int'] += 1
+		}
 		$if method.return_type is int {
 			assert method.name in ['int_method1', 'int_method2']
 		}
+		$if method.typ is fn (string) {
+			methods_found['fn(string)'] += 1
+		}
 		$if method.args[0].typ is string {
 			assert method.name == 'string_arg'
 		}
 	}
+	assert methods_found['fn()'] == 2
+	assert methods_found['fn() int'] == 2
+	assert methods_found['fn(string)'] == 1
 }
 
 fn test_comptime_for_fields() {