From 805da2325f8d2102b19c07b4b4a0210f1a5790df Mon Sep 17 00:00:00 2001
From: joe-conigliaro <joe@vlang.io>
Date: Tue, 8 Dec 2020 14:21:19 +1100
Subject: [PATCH] cgen: defer was broken in presence of anon fn. fixed #7171

---
 vlib/v/gen/fn.v           |  9 ++++++++-
 vlib/v/tests/defer_test.v | 24 ++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/vlib/v/gen/fn.v b/vlib/v/gen/fn.v
index f63d8d8bf0..c115a5d66d 100644
--- a/vlib/v/gen/fn.v
+++ b/vlib/v/gen/fn.v
@@ -149,11 +149,19 @@ fn (mut g Gen) gen_fn_decl(it ast.FnDecl, skip bool) {
 	if g.pref.is_prof {
 		g.profile_fn(it)
 	}
+	// we could be in an anon fn so save outer fn defer stmts
+	prev_defer_stmts := g.defer_stmts
+	g.defer_stmts = []
 	g.stmts(it.stmts)
 	//
 	if it.return_type == table.void_type {
 		g.write_defer_stmts_when_needed()
 	}
+	if it.is_anon {
+		g.defer_stmts = prev_defer_stmts
+	} else {
+		g.defer_stmts = []
+	}
 	if it.return_type != table.void_type && it.stmts.len > 0 && it.stmts.last() !is ast.Return {
 		default_expr := g.type_default(it.return_type)
 		// TODO: perf?
@@ -164,7 +172,6 @@ fn (mut g Gen) gen_fn_decl(it ast.FnDecl, skip bool) {
 		}
 	}
 	g.writeln('}')
-	g.defer_stmts = []
 	if g.pref.printfn_list.len > 0 && g.last_fn_c_name in g.pref.printfn_list {
 		println(g.out.after(fn_start_pos))
 	}
diff --git a/vlib/v/tests/defer_test.v b/vlib/v/tests/defer_test.v
index 684dc9f6e7..1289d228a6 100644
--- a/vlib/v/tests/defer_test.v
+++ b/vlib/v/tests/defer_test.v
@@ -45,6 +45,10 @@ mut:
 	val int
 }
 
+fn (n Num) add(i int) int {
+	return n.val + i
+}
+
 fn test_defer_early_exit() {
 	mut sum := Num{0}
 	for i in 0 .. 10 {
@@ -59,3 +63,23 @@ fn test_defer_option() {
 	set_num_opt(mut ok) or {}
 	assert ok.val == 1
 }
+
+fn test_defer_with_anon_fn() {
+	mut f := &Num{val: 110}
+	defer {
+		assert f.add(1) == 111
+	}
+	go fn () {
+		defer {
+			println('deferred 1')
+		}
+	}()
+	x := fn () {
+		defer {
+			println('defered 2')
+		}
+		return
+	}
+	x()
+	return
+}
\ No newline at end of file