From f3d8bbdf3d964d975ed0b908152a7fcbb8f7a42c Mon Sep 17 00:00:00 2001
From: yuyi <yuyi98@163.com>
Date: Tue, 11 Jan 2022 22:25:16 +0800
Subject: [PATCH] cgen: fix `$if T.typ is Type {` (#13135)

---
 vlib/v/gen/c/comptime.v                        |  6 +++++-
 ...comptime_if_expr_generic_typ_is_type_test.v | 18 ++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)
 create mode 100644 vlib/v/tests/comptime_if_expr_generic_typ_is_type_test.v

diff --git a/vlib/v/gen/c/comptime.v b/vlib/v/gen/c/comptime.v
index ac4443e9c6..5ccad7f12a 100644
--- a/vlib/v/gen/c/comptime.v
+++ b/vlib/v/gen/c/comptime.v
@@ -375,7 +375,11 @@ fn (mut g Gen) comptime_if_cond(cond ast.Expr, pkg_exist bool) bool {
 						}
 					} else if left is ast.SelectorExpr {
 						name = '${left.expr}.$left.field_name'
-						exp_type = g.comptime_var_type_map[name]
+						if left.gkind_field == .typ {
+							exp_type = g.unwrap_generic(left.name_type)
+						} else {
+							exp_type = g.comptime_var_type_map[name]
+						}
 					} else if left is ast.TypeNode {
 						// this is only allowed for generics currently, otherwise blocked by checker
 						exp_type = g.unwrap_generic(left.typ)
diff --git a/vlib/v/tests/comptime_if_expr_generic_typ_is_type_test.v b/vlib/v/tests/comptime_if_expr_generic_typ_is_type_test.v
new file mode 100644
index 0000000000..63d61ff21a
--- /dev/null
+++ b/vlib/v/tests/comptime_if_expr_generic_typ_is_type_test.v
@@ -0,0 +1,18 @@
+module main
+
+fn write<T>(out T) string {
+	$if T.typ is bool {
+		println('FOO')
+		return 'FOO'
+	} $else $if T.typ !is bool {
+		println('BAR')
+		return 'BAR'
+	}
+	return 'EMPTY'
+}
+
+fn test_comptime_if_expr_generic_typ_is_type() {
+	mut val := false
+	ret := write<bool>(val)
+	assert ret == 'FOO'
+}