From 51907618c3fd66f1e703120bba0d54527e54dd6f Mon Sep 17 00:00:00 2001
From: Felipe Pena <felipensp@gmail.com>
Date: Mon, 9 Jan 2023 17:30:35 -0300
Subject: [PATCH] cgen: fix code generated for a match expression, which
 returns function (#16922)

---
 vlib/v/gen/c/match.v                | 15 ++++-
 vlib/v/tests/match_return_fn_test.v | 96 +++++++++++++++++++++++++++++
 2 files changed, 110 insertions(+), 1 deletion(-)
 create mode 100644 vlib/v/tests/match_return_fn_test.v

diff --git a/vlib/v/gen/c/match.v b/vlib/v/gen/c/match.v
index ffbdce28ad..5e75c1531a 100644
--- a/vlib/v/gen/c/match.v
+++ b/vlib/v/gen/c/match.v
@@ -87,7 +87,20 @@ fn (mut g Gen) match_expr(node ast.MatchExpr) {
 		g.empty_line = true
 		cur_line = g.go_before_stmt(0).trim_left(' \t')
 		tmp_var = g.new_tmp_var()
-		g.writeln('${g.typ(node.return_type)} ${tmp_var} = ${g.type_default(node.return_type)};')
+		mut func_decl := ''
+		if g.table.final_sym(node.return_type).kind == .function {
+			func_sym := g.table.final_sym(node.return_type)
+			if func_sym.info is ast.FnType {
+				def := g.fn_var_signature(func_sym.info.func.return_type, func_sym.info.func.params.map(it.typ),
+					tmp_var)
+				func_decl = '${def} = &${g.typ(node.return_type)};'
+			}
+		}
+		if func_decl.len > 0 {
+			g.writeln(func_decl) // func, anon func declaration
+		} else {
+			g.writeln('${g.typ(node.return_type)} ${tmp_var} = ${g.type_default(node.return_type)};')
+		}
 		g.empty_line = true
 		if g.infix_left_var_name.len > 0 {
 			g.writeln('if (${g.infix_left_var_name}) {')
diff --git a/vlib/v/tests/match_return_fn_test.v b/vlib/v/tests/match_return_fn_test.v
new file mode 100644
index 0000000000..cba1a6e5ef
--- /dev/null
+++ b/vlib/v/tests/match_return_fn_test.v
@@ -0,0 +1,96 @@
+enum Foo {
+	a
+	b
+	c
+	d
+	e
+	f
+}
+
+fn test() string {
+	return 'c'
+}
+
+fn dummy() string {
+	return 'b'
+}
+
+fn dummy2() string {
+	return 'a'
+}
+
+fn dummy3() {}
+
+fn err() fn () string {
+	return match Foo.a {
+		.a { dummy }
+		.b { dummy }
+		.c { dummy }
+		.d { dummy2 }
+		.e { dummy2 }
+		else { dummy2 }
+	}
+}
+
+fn err2() fn () string {
+	return match Foo.d {
+		.a { dummy }
+		.b { dummy }
+		.c { dummy }
+		.d { dummy2 }
+		.e { dummy2 }
+		.f { dummy }
+	}
+}
+
+fn err3() fn () string {
+	return match Foo.f {
+		.a { dummy }
+		.b { dummy }
+		.c { dummy }
+		.d { dummy }
+		.e { dummy }
+		else { test }
+	}
+}
+
+fn err4() fn () {
+	return match Foo.f {
+		.a { dummy3 }
+		.b { dummy3 }
+		.c { dummy3 }
+		.d { dummy3 }
+		.e { dummy3 }
+		else { dummy3 }
+	}
+}
+
+fn err5(f fn ()) fn () {
+	return match Foo.f {
+		.a { dummy3 }
+		.b { dummy3 }
+		.c { dummy3 }
+		.d { dummy3 }
+		.e { dummy3 }
+		else { f }
+	}
+}
+
+fn test_main() {
+	var := main.err()()
+	assert var == 'b'
+
+	var2 := main.err2()()
+	assert var2 == 'a'
+
+	var3 := main.err3()()
+	assert var3 == 'c'
+
+	var4 := err4()
+	assert var4 == dummy3
+
+	anon := fn () {}
+	var5 := err5(anon)
+	assert var5 == anon
+	var5()
+}