Test refactoring

compiler/testData/diagnostics/tests/smartCasts/kt2865.kt

@@ -0,0 +1,11 @@
+fun <K, V> MutableMap<K, V>.set(k: K, v: V) {}
+
+fun foo(a: MutableMap<String, String>, x: String?) {
+    a[x!!] = <!DEBUG_INFO_SMARTCAST!>x<!>
+    a[<!DEBUG_INFO_SMARTCAST!>x<!>] = x<!UNNECESSARY_NOT_NULL_ASSERTION!>!!<!>
+}
+
+fun foo1(a: MutableMap<String, String>, x: String?) {
+    <!TYPE_INFERENCE_CONFLICTING_SUBSTITUTIONS!>a[x]<!> = x!!
+    a[x<!UNNECESSARY_NOT_NULL_ASSERTION!>!!<!>] = <!DEBUG_INFO_SMARTCAST!>x<!>
+}