Prohibit renaming operator to another operator on import.

compiler/testData/diagnostics/tests/imports/OperatorRenameOnImport.kt

@@ -0,0 +1,16 @@
+// !DIAGNOSTICS: -UNUSED_PARAMETER
+// FILE: a.kt
+package a
+
+interface A
+
+operator fun A.plus(other: A): A = this
+
+// FILE: b.kt
+package b
+
+import a.A
+import a.<!OPERATOR_RENAMED_ON_IMPORT!>plus<!> as minus
+
+fun test(a1: A, a2: A) =
+        a1 - a2

compiler/testData/diagnostics/tests/imports/OperatorRenameOnImport.txt

@@ -0,0 +1,15 @@
+package
+
+package a {
+    public operator fun a.A.plus(/*0*/ other: a.A): a.A
+
+    public interface A {
+        public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+        public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+        public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+    }
+}
+
+package b {
+    public fun test(/*0*/ a1: a.A, /*1*/ a2: a.A): a.A
+}