Navigate to receiver from this in extension function (KT-16991)

#KT-16991 Fixed
 #KT-13013 In Progress

idea/src/org/jetbrains/kotlin/idea/search/ideaExtensions/KotlinTargetElementEvaluator.kt

@@ -23,6 +23,7 @@ import com.intellij.psi.PsiElement
 import com.intellij.psi.PsiFile
 import com.intellij.psi.PsiReference
 import com.intellij.util.BitUtil
+import org.jetbrains.kotlin.descriptors.CallableDescriptor
 import org.jetbrains.kotlin.descriptors.DeclarationDescriptorWithSource
 import org.jetbrains.kotlin.idea.intentions.isAutoCreatedItUsage
 import org.jetbrains.kotlin.idea.references.KtDestructuringDeclarationReference
@@ -32,6 +33,7 @@ import org.jetbrains.kotlin.psi.psiUtil.containingClassOrObject
 import org.jetbrains.kotlin.psi.psiUtil.getNonStrictParentOfType
 import org.jetbrains.kotlin.psi.psiUtil.getParentOfTypeAndBranch
 import org.jetbrains.kotlin.psi.psiUtil.isAbstract
+import org.jetbrains.kotlin.resolve.descriptorUtil.isExtension
 import org.jetbrains.kotlin.resolve.source.getPsi
 
 class KotlinTargetElementEvaluator : TargetElementEvaluatorEx {
@@ -48,6 +50,20 @@ class KotlinTargetElementEvaluator : TargetElementEvaluatorEx {
             val lambdaExpression = descriptorWithSource.source.getPsi()?.parent as? KtLambdaExpression ?: return null
             return lambdaExpression.leftCurlyBrace.treeNext?.psi
         }
+
+        // Navigate to receiver element for this in extension declaration
+        fun findReceiverForThisInExtensionFunction(ref: PsiReference): PsiElement? {
+            val element: PsiElement = ref.element
+            if (element.text != "this") return null
+
+            if (element !is KtNameReferenceExpression) return null
+            val callableDescriptor = element.resolveMainReferenceToDescriptors().singleOrNull() as? CallableDescriptor ?: return null
+
+            if (!callableDescriptor.isExtension) return null
+            val callableDeclaration = callableDescriptor.source.getPsi() as? KtCallableDeclaration ?: return null
+
+            return callableDeclaration.receiverTypeReference
+        }
     }
 
     override fun includeSelfInGotoImplementation(element: PsiElement): Boolean = !(element is KtClass && element.isAbstract())
@@ -67,7 +83,8 @@ class KotlinTargetElementEvaluator : TargetElementEvaluatorEx {
         }
 
         if (BitUtil.isSet(flags, TargetElementUtil.REFERENCED_ELEMENT_ACCEPTED)) {
-            return findLambdaOpenLBraceForGeneratedIt(ref)
+            return findLambdaOpenLBraceForGeneratedIt(ref) ?:
+                   findReceiverForThisInExtensionFunction(ref)
         }
 
         return null

idea/testData/navigation/gotoDeclaration/labeledThisToClass.test

@@ -0,0 +1,13 @@
+// FILE: before.kt
+class A {
+    fun String.foo() {
+        this<caret>@A
+    }
+}
+
+// FILE: after.kt
+class <caret>A {
+    fun String.foo() {
+        this@A
+    }
+}

idea/testData/navigation/gotoDeclaration/labeledThisToMemberExtension.test

@@ -0,0 +1,13 @@
+// FILE: before.kt
+class A {
+    fun String.foo() {
+        this<caret>@foo
+    }
+}
+
+// FILE: after.kt
+class A {
+    fun <caret>String.foo() {
+        this@foo
+    }
+}

idea/testData/navigation/gotoDeclaration/thisExtensionFunction.test

@@ -0,0 +1,18 @@
+// FILE: before.kt
+interface Foo
+
+fun foo(a: Any) {}
+
+fun Foo.bar() {
+    foo(this<caret>)
+}
+
+
+// FILE: after.kt
+interface Foo
+
+fun foo(a: Any) {}
+
+fun <caret>Foo.bar() {
+    foo(this)
+}

idea/testData/navigation/gotoDeclaration/thisExtensionLambda.test

@@ -0,0 +1,21 @@
+// FILE: before.kt
+interface Foo
+
+fun foo(a: Foo.() -> Unit) {}
+
+fun bar() {
+    foo {
+        <caret>this
+    }
+}
+
+// FILE: after.kt
+interface Foo
+
+fun foo(a: Foo.() -> Unit) {}
+
+fun bar() {
+    foo <caret>{
+        this
+    }
+}

idea/testData/navigation/gotoDeclaration/thisInExtensionPropertyAccessor.test

@@ -0,0 +1,7 @@
+// FILE: before.kt
+val String.test: String
+    get() { return <caret>this }
+
+// FILE: after.kt
+val <caret>String.test: String
+    get() { return this }

idea/tests/org/jetbrains/kotlin/idea/navigation/GotoDeclarationTestGenerated.java

@@ -65,4 +65,34 @@ public class GotoDeclarationTestGenerated extends AbstractGotoDeclarationTest {
         String fileName = KotlinTestUtils.navigationMetadata("idea/testData/navigation/gotoDeclaration/itParameterInLambda.test");
         doTest(fileName);
     }
+
+    @TestMetadata("labeledThisToClass.test")
+    public void testLabeledThisToClass() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("idea/testData/navigation/gotoDeclaration/labeledThisToClass.test");
+        doTest(fileName);
+    }
+
+    @TestMetadata("labeledThisToMemberExtension.test")
+    public void testLabeledThisToMemberExtension() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("idea/testData/navigation/gotoDeclaration/labeledThisToMemberExtension.test");
+        doTest(fileName);
+    }
+
+    @TestMetadata("thisExtensionFunction.test")
+    public void testThisExtensionFunction() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("idea/testData/navigation/gotoDeclaration/thisExtensionFunction.test");
+        doTest(fileName);
+    }
+
+    @TestMetadata("thisExtensionLambda.test")
+    public void testThisExtensionLambda() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("idea/testData/navigation/gotoDeclaration/thisExtensionLambda.test");
+        doTest(fileName);
+    }
+
+    @TestMetadata("thisInExtensionPropertyAccessor.test")
+    public void testThisInExtensionPropertyAccessor() throws Exception {
+        String fileName = KotlinTestUtils.navigationMetadata("idea/testData/navigation/gotoDeclaration/thisInExtensionPropertyAccessor.test");
+        doTest(fileName);
+    }
 }