compiler: allow to call methods on return values

Signed-off-by: Evgeniy Stratonikov <evgeniy@nspcc.ru>

pkg/compiler/testdata/method/struct.go

@@ -0,0 +1,16 @@
+package method
+
+// X is some type.
+type X struct {
+	a int
+}
+
+// GetA returns the value of a.
+func (x X) GetA() int {
+	return x.a
+}
+
+// NewX creates a new X instance.
+func NewX() X {
+	return X{a: 42}
+}