cgen: make use of mut_rec in method consistent (#9308)

vlib/v/gen/c/cgen.v

@@ -4498,9 +4498,8 @@ fn (mut g Gen) return_statement(node ast.Return) {
 		}
 		if expr0.is_auto_deref_var() {
 			if g.fn_decl.return_type.is_ptr() {
-				g.write('&(*')
+				var_str := g.expr_string(expr0)
-				g.expr(expr0)
+				g.write(var_str.trim('&'))
-				g.write(')')
 			} else {
 				g.write('*')
 				g.expr(expr0)

vlib/v/tests/mut_receiver_returned_as_reference_test.v

@@ -0,0 +1,36 @@
+struct Player {
+mut:
+	name string
+	x    int
+	y    int
+}
+
+fn (mut p Player) set_name(name string) &Player {
+	p.name = name
+	return p // because of automatic (de)reference of return values
+}
+
+// NB: `p` is declared as a `mut` parameter, 
+// which now only affects its mutability.
+fn (mut p Player) set_position(x int, y int) &Player {
+	p.x = x
+	p.y = y
+	// TODO: from the point of view of the V programmer,
+	// `p` has still type &Player.
+	// assert typeof(p).name == 'Player'
+	return &p
+}
+
+fn test_mut_receiver() {
+	mut p := &Player{}
+	f := p.set_name('frodo')
+	assert u64(p) == u64(f)
+	z := p.set_position(111, 222)
+	assert u64(p) == u64(z)
+	//
+	assert p.name == 'frodo'
+	assert p.x == 111
+	assert p.y == 222
+	assert u64(p.set_name('bilbo')) == u64(p)
+	assert p.name == 'bilbo'
+}