From b2538e83da4b7ab9c39c8726a60ebcca307612ef Mon Sep 17 00:00:00 2001
From: yuyi <yuyi98@163.com>
Date: Tue, 4 Jan 2022 22:04:15 +0800
Subject: [PATCH] checker: fix generic fn using generic type in if expr
 (#13027)

---
 vlib/v/checker/comptime.v                        |  2 +-
 vlib/v/checker/if.v                              |  2 +-
 .../generic_fn_using_generic_type_in_if_test.v   | 16 ++++++++++++++++
 3 files changed, 18 insertions(+), 2 deletions(-)
 create mode 100644 vlib/v/tests/generic_fn_using_generic_type_in_if_test.v

diff --git a/vlib/v/checker/comptime.v b/vlib/v/checker/comptime.v
index 180909c0f1..dac55459a8 100644
--- a/vlib/v/checker/comptime.v
+++ b/vlib/v/checker/comptime.v
@@ -547,7 +547,7 @@ fn (mut c Checker) comptime_if_branch(cond ast.Expr, pos token.Position) bool {
 					return false
 				}
 				// `$if some_var {}`, or `[if user_defined_tag] fn abc(){}`
-				typ := c.expr(cond)
+				typ := c.unwrap_generic(c.expr(cond))
 				if cond.obj !is ast.Var && cond.obj !is ast.ConstField
 					&& cond.obj !is ast.GlobalField {
 					if !c.inside_ct_attr {
diff --git a/vlib/v/checker/if.v b/vlib/v/checker/if.v
index a22f72380d..02ef3e4195 100644
--- a/vlib/v/checker/if.v
+++ b/vlib/v/checker/if.v
@@ -39,7 +39,7 @@ pub fn (mut c Checker) if_expr(mut node ast.IfExpr) ast.Type {
 			} else {
 				// check condition type is boolean
 				c.expected_type = ast.bool_type
-				cond_typ := c.expr(branch.cond)
+				cond_typ := c.unwrap_generic(c.expr(branch.cond))
 				if (cond_typ.idx() != ast.bool_type_idx || cond_typ.has_flag(.optional))
 					&& !c.pref.translated {
 					c.error('non-bool type `${c.table.type_to_str(cond_typ)}` used as if condition',
diff --git a/vlib/v/tests/generic_fn_using_generic_type_in_if_test.v b/vlib/v/tests/generic_fn_using_generic_type_in_if_test.v
new file mode 100644
index 0000000000..bd316fa934
--- /dev/null
+++ b/vlib/v/tests/generic_fn_using_generic_type_in_if_test.v
@@ -0,0 +1,16 @@
+fn test_generic_fn_using_generic_type_in_if() {
+	ret := generic_bool(true)
+	assert ret == 'true'
+}
+
+fn generic_bool<T>(val T) string {
+	$if T is bool {
+		if val {
+			println('is true')
+			return 'true'
+		} else {
+			println('is false')
+			return 'false'
+		}
+	}
+}