PSI Unifier: Fix matching of this-expressions

#KT-8293 Fixed

idea/ide-common/src/org/jetbrains/kotlin/idea/util/psi/patternMatching/KotlinPsiUnifier.kt

@@ -365,6 +365,7 @@ class KotlinPsiUnifier(
                     else -> false
                 }
                 this is KtBinaryExpression -> operationReference.getReferencedNameElementType() == KtTokens.ELVIS
+                this is KtThisExpression -> true
                 else -> false
             }
         }
@@ -423,6 +424,12 @@ class KotlinPsiUnifier(
             return matchDescriptors(d1, d2)
         }
 
+        private fun matchThisExpressions(e1: KtThisExpression, e2: KtThisExpression): Boolean {
+            val d1 = e1.bindingContext[BindingContext.REFERENCE_TARGET, e1.instanceReference]
+            val d2 = e2.bindingContext[BindingContext.REFERENCE_TARGET, e2.instanceReference]
+            return matchDescriptors(d1, d2)
+        }
+
         private fun matchDestructuringDeclarations(e1: KtDestructuringDeclaration, e2: KtDestructuringDeclaration): Boolean {
             val entries1 = e1.entries
             val entries2 = e2.entries
@@ -694,6 +701,8 @@ class KotlinPsiUnifier(
                 e1 is KtCallableReferenceExpression && e2 is KtCallableReferenceExpression ->
                     if (matchCallableReferences(e1, e2)) MATCHED else UNMATCHED
 
+                e1 is KtThisExpression && e2 is KtThisExpression -> if (matchThisExpressions(e1, e2)) MATCHED else UNMATCHED
+
                 else ->
                     matchCalls(e1, e2)
             }

idea/testData/refactoring/introduceVariable/thisAsCallee.kt

@@ -0,0 +1,6 @@
+fun (String.() -> String).foo(x : String) {
+    x.<selection>this</selection>()
+    x.this@foo()
+    val t = this
+    val tt = this@foo
+}

idea/testData/refactoring/introduceVariable/thisAsCallee.kt.after

@@ -0,0 +1,7 @@
+fun (String.() -> String).foo(x : String) {
+    val function = this
+    x.function()
+    x.function()
+    val t = function
+    val tt = function
+}

idea/testData/unifier/equivalence/expressions/this/thisAsCallee.kt

@@ -0,0 +1,8 @@
+// DISABLE-ERRORS
+fun (String.() -> String).foo(x : String) {
+    x.<selection>this</selection>()
+    x.this()
+    x.this(1)
+    x.this@foo()
+    x.this@foo(2)
+}

idea/testData/unifier/equivalence/expressions/this/thisAsCallee.kt.match

@@ -0,0 +1,9 @@
+this
+
+this
+
+this
+
+this@foo
+
+this@foo

idea/tests/org/jetbrains/kotlin/idea/refactoring/introduce/ExtractionTestGenerated.java

@@ -379,6 +379,12 @@ public class ExtractionTestGenerated extends AbstractExtractionTest {
             doIntroduceVariableTest(fileName);
         }
 
+        @TestMetadata("thisAsCallee.kt")
+        public void testThisAsCallee() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/refactoring/introduceVariable/thisAsCallee.kt");
+            doIntroduceVariableTest(fileName);
+        }
+
         @TestMetadata("ThisReference.kt")
         public void testThisReference() throws Exception {
             String fileName = KotlinTestUtils.navigationMetadata("idea/testData/refactoring/introduceVariable/ThisReference.kt");

idea/tests/org/jetbrains/kotlin/psi/patternMatching/PsiUnifierTestGenerated.java

@@ -715,6 +715,12 @@ public class PsiUnifierTestGenerated extends AbstractPsiUnifierTest {
                     String fileName = KotlinTestUtils.navigationMetadata("idea/testData/unifier/equivalence/expressions/this/simpleThis2Runtime.kt");
                     doTest(fileName);
                 }
+
+                @TestMetadata("thisAsCallee.kt")
+                public void testThisAsCallee() throws Exception {
+                    String fileName = KotlinTestUtils.navigationMetadata("idea/testData/unifier/equivalence/expressions/this/thisAsCallee.kt");
+                    doTest(fileName);
+                }
             }
         }