From 31d03bb113e89025d46921b0d0f2f90871b94ab8 Mon Sep 17 00:00:00 2001
From: joe-conigliaro <joe.conigliaro@gmail.com>
Date: Sat, 6 Jun 2020 12:24:27 +1000
Subject: [PATCH] checker/cgen: small generic fixes (mut arg return)

---
 vlib/v/checker/checker.v     | 15 ++++-----------
 vlib/v/gen/fn.v              |  2 +-
 vlib/v/tests/generics_test.v |  6 +++---
 3 files changed, 8 insertions(+), 15 deletions(-)

diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 00e41a393f..5a103078a8 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -1226,7 +1226,7 @@ pub fn (mut c Checker) return_stmt(mut return_stmt ast.Return) {
 	if return_stmt.exprs.len == 0 {
 		return
 	}
-	expected_type := c.expected_type
+	expected_type := c.unwrap_generic(c.expected_type)
 	expected_type_sym := c.table.get_type_symbol(expected_type)
 	exp_is_optional := expected_type.has_flag(.optional)
 	mut expected_types := [expected_type]
@@ -1257,23 +1257,16 @@ pub fn (mut c Checker) return_stmt(mut return_stmt ast.Return) {
 		return
 	}
 	for i, exp_type in expected_types {
-		got_typ := got_types[i]
+		got_typ := c.unwrap_generic(got_types[i])
 		if got_typ.has_flag(.optional) &&
 			(!exp_type.has_flag(.optional) || c.table.type_to_str(got_typ) != c.table.type_to_str(exp_type)) {
 			pos := return_stmt.exprs[i].position()
 			c.error('cannot use `${c.table.type_to_str(got_typ)}` as type `${c.table.type_to_str(exp_type)}` in return argument', pos)
 		}
-		is_generic := exp_type == table.t_type
-		ok := if is_generic { c.check_types(got_typ, c.cur_generic_type) || got_typ == exp_type } else { c.check_types(got_typ,
-				exp_type) }
-		// ok := c.check_types(got_typ, exp_type)
-		if !ok { // !c.table.check(got_typ, exp_typ) {
+		if !c.check_types(got_typ, exp_type) {
 			got_typ_sym := c.table.get_type_symbol(got_typ)
 			mut exp_typ_sym := c.table.get_type_symbol(exp_type)
 			pos := return_stmt.exprs[i].position()
-			if is_generic {
-				exp_typ_sym = c.table.get_type_symbol(c.cur_generic_type)
-			}
 			if exp_typ_sym.kind == .interface_ {
 				c.type_implements(got_typ, exp_type, return_stmt.pos)
 				continue
@@ -1747,7 +1740,7 @@ fn (mut c Checker) stmts(stmts []ast.Stmt) {
 	c.expected_type = table.void_type
 }
 
-pub fn (mut c Checker) unwrap_generic(typ table.Type) table.Type {
+pub fn (c &Checker) unwrap_generic(typ table.Type) table.Type {
 	if typ.idx() == table.t_type_idx {
 		// return c.cur_generic_type
 		// its more efficient to set the id rather than to copy flags/nr_muls
diff --git a/vlib/v/gen/fn.v b/vlib/v/gen/fn.v
index 6f97481ad2..2a4780e11c 100644
--- a/vlib/v/gen/fn.v
+++ b/vlib/v/gen/fn.v
@@ -328,7 +328,7 @@ fn (mut g Gen) call_expr(node ast.CallExpr) {
 	}
 }
 
-pub fn (mut g Gen) unwrap_generic(typ table.Type) table.Type {
+pub fn (g &Gen) unwrap_generic(typ table.Type) table.Type {
 	if typ.idx() == table.t_type_idx {
 		// return g.cur_generic_type
 		// its more efficient to set the id rather than to copy flags/nr_muls
diff --git a/vlib/v/tests/generics_test.v b/vlib/v/tests/generics_test.v
index c381e6a1b7..5ad70b2634 100644
--- a/vlib/v/tests/generics_test.v
+++ b/vlib/v/tests/generics_test.v
@@ -68,18 +68,18 @@ fn mut_arg<T>(mut x T) {
 	println(x.foo) // = 'foo'
 }
 
-/*
+
 fn mut_arg2<T>(mut x T) T {
 	println(x.foo) // = 'foo'
 	return x
 }
-*/
+
 fn test_create() {
 	create<User>()
 	create<City>()
 	u := User{}
 	mut_arg<User>(mut u)
-	// mut_arg2<User>(mut u)
+	mut_arg2<User>(mut u)
 }
 
 /*