checker: fix match expr with enum type value (#13683)

vlib/v/checker/checker.v

@@ -68,6 +68,7 @@ pub mut:
 	error_lines        []int // to avoid printing multiple errors for the same line
 	expected_type      ast.Type
 	expected_or_type   ast.Type // fn() or { 'this type' } eg. string. expected or block type
+	expected_expr_type ast.Type // if/match is_expr: expected_type
 	mod                string   // current module name
 	const_decl         string
 	const_deps         []string
@@ -3835,7 +3836,11 @@ pub fn (mut c Checker) index_expr(mut node ast.IndexExpr) ast.Type {
 // with this value.
 pub fn (mut c Checker) enum_val(mut node ast.EnumVal) ast.Type {
 	mut typ_idx := if node.enum_name == '' {
+		if c.expected_type == ast.void_type && c.expected_expr_type != ast.void_type {
+			c.expected_expr_type.idx()
+		} else {
 			c.expected_type.idx()
+		}
 	} else {
 		c.table.find_type_idx(node.enum_name)
 	}

vlib/v/checker/match.v

@@ -13,6 +13,12 @@ pub fn (mut c Checker) match_expr(mut node ast.MatchExpr) ast.Type {
 		c.error('unnecessary `()` in `match` condition, use `match expr {` instead of `match (expr) {`.',
 			node.cond.pos)
 	}
+	if node.is_expr {
+		c.expected_expr_type = c.expected_type
+		defer {
+			c.expected_expr_type = ast.void_type
+		}
+	}
 	cond_type := c.expr(node.cond)
 	// we setting this here rather than at the end of the method
 	// since it is used in c.match_exprs() it saves checking twice

vlib/v/tests/match_expr_with_enum_test.v

@@ -0,0 +1,24 @@
+enum Foo {
+	a
+	b
+	c
+}
+
+fn get() Foo {
+	return .a
+}
+
+fn foo(f Foo) string {
+	println(f)
+	return '$f'
+}
+
+fn test_match_expr_with_enum() {
+	ret := foo(match get() {
+		.a { .b }
+		.b { .c }
+		.c { .a }
+	})
+	println(ret)
+	assert ret == 'b'
+}