KT-1875 Safe call should be binded with receiver or this object (but not with both by default)

#KT-1875 fixed

compiler/testData/diagnostics/tests/extensions/kt1875.jet

@@ -0,0 +1,21 @@
+//KT-1875 Safe call should be binded with receiver or this object (but not with both by default)
+
+package kt1875
+
+fun f(a : Int?, b : Int.(Int)->Int) = a?.b(1) //unnecessary safe call warning
+
+trait T {
+    val f : ((i: Int) -> Unit)?
+}
+
+fun test(t: T) {
+    t.<!UNSAFE_CALL!>f<!>(1) //unsafe call error
+    t.f?.invoke(1)
+}
+
+fun test1(t: T?) {
+    t<!UNSAFE_CALL!>.<!><!UNSAFE_CALL!>f<!>(1)
+    t?.<!UNSAFE_CALL!>f<!>(1)
+    t<!UNSAFE_CALL!>.<!>f?.invoke(1)
+    t?.f?.invoke(1)
+}