Deprecate extension annotation in favor of Extension

idea/idea-completion/testData/basic/multifile/ExcludedClass/ExcludedClass.dependency.kt

@@ -1,5 +1,5 @@
 package somePackage
 
 class ExcludedClass
-
-class ExtraClass
+// Such strange name here needed to make completion prefix not intersecting with kotlin.Extension
+class ExctraClass

idea/idea-completion/testData/basic/multifile/ExcludedClass/ExcludedClass.kt

@@ -1,4 +1,4 @@
-val x = Ex<caret>
+val x = Exc<caret>
 
 // ABSENT: ExcludedClass
-// EXIST: ExtraClass
+// EXIST: ExctraClass

idea/idea-completion/testData/basic/multifile/ExcludedJavaClass/ExcludedJavaClass.kt

@@ -1,4 +1,4 @@
-val x = Ex<caret>
+val x = Exc<caret>
 
 // ABSENT: ExcludedClass
-// EXIST: ExtraClass
+// EXIST: ExctraClass

idea/idea-completion/testData/basic/multifile/ExcludedJavaClass/somePackage/ExctraClass.java

@@ -0,0 +1,6 @@
+package somePackage;
+
+// Such strange name here needed to make completion prefix not intersecting with kotlin.Extension
+public class ExctraClass {
+
+}

idea/idea-completion/testData/basic/multifile/ExcludedJavaClass/somePackage/ExtraClass.java

@@ -1,5 +0,0 @@
-package somePackage;
-
-public class ExtraClass {
-
-}

idea/idea-completion/testData/basic/multifile/NotImportedExtensionFunction2/NotImportedExtensionFunction2.dependency.kt

@@ -6,7 +6,7 @@ fun (() -> Unit)?.helloFun1() {
 fun Function0<Unit>.helloFun2() {
 }
 
-fun @extension Function1<String, Unit>.helloFun3() {
+fun @Extension Function1<String, Unit>.helloFun3() {
 }
 
 fun Function1<String, Unit>.helloFun4() {

idea/idea-completion/testData/basic/multifile/NotImportedExtensionFunction3/NotImportedExtensionFunction3.dependency.kt

@@ -6,10 +6,10 @@ fun (String.() -> Unit)?.helloFun1() {
 fun Function0<Unit>.helloFun2() {
 }
 
-fun @extension Function1<String, Unit>.helloFun3() {
+fun @Extension Function1<String, Unit>.helloFun3() {
 }
 
-fun @extension Function1<Int, Unit>.helloFun4() {
+fun @Extension Function1<Int, Unit>.helloFun4() {
 }
 
 fun Function1<String, Unit>.helloFun5() {

idea/testData/decompiler/decompiledText/FunctionTypes/FunctionTypes.kt

@@ -21,9 +21,9 @@ class FunctionTypes {
     public fun f2(f: Function2<Int, *, String>) {
     }
 
-    public fun f3(f: @extension Function2<Int, Int, Unit>) {
+    public fun f3(f: @Extension Function2<Int, Int, Unit>) {
     }
 
-    public fun f4(f: List<@extension Function1<*, *>>) {
+    public fun f4(f: List<@Extension Function1<*, *>>) {
     }
 }

idea/testData/decompiler/stubBuilder/Types/Types.kt

@@ -19,7 +19,7 @@ abstract class Types {
 
     abstract val starList: List<*>
     abstract val starFun: Function1<*, *>
-    abstract val extFun: @extension Function2<Int, Int, Unit>
-    abstract val listExtStarFun: List<@extension Function1<*, *>>
+    abstract val extFun: @Extension Function2<Int, Int, Unit>
+    abstract val listExtStarFun: List<@Extension Function1<*, *>>
     abstract val funTypeWithStarAndNonStar: Function1<*, Int>
 }

idea/testData/unifier/equivalence/types/function0.kt

@@ -4,4 +4,4 @@ val c: <selection>() -> String</selection> = { "" }
 val d: () -> kotlin.String = { "" }
 val e: () -> Unit = {  }
 val f: Any.() -> String = { "" }
-val g: @extension Function1<String, String> = { "" }
+val g: @Extension Function1<String, String> = { "" }

idea/testData/unifier/equivalence/types/function1.kt

@@ -5,6 +5,6 @@ val d: (n: Int) -> kotlin.String = { "" }
 val e: (String) -> Int = { 0 }
 val f: () -> Int = { 0 }
 val g: Int.() -> String = { "" }
-val h: @extension Function2<Int, Int, String> = { "" }
+val h: @Extension Function2<Int, Int, String> = { "" }
 val i: (m: Int) -> kotlin.String = { "" }
-val j: @extension Function1<Int, String> = { "" }
+val j: @Extension Function1<Int, String> = { "" }

idea/testData/unifier/equivalence/types/function1.kt.match

@@ -10,4 +10,4 @@ Int.() -> String
 
 (m: Int) -> kotlin.String
 
-@extension Function1<Int, String>
+@Extension Function1<Int, String>

idea/testData/unifier/equivalence/types/function2.kt

@@ -6,6 +6,6 @@ val e: (String) -> Int = { 0 }
 val f: () -> Int = { 0 }
 val g: Any.(Int) -> String = { "" }
 val h: Int.(Any) -> String = { "" }
-val i: @extension Function3<Any, Any, Int, String> = { a, b -> "" }
+val i: @Extension Function3<Any, Any, Int, String> = { a, b -> "" }
 val j: (t: Any, u: Int) -> kotlin.String = { a, b ->  "" }
-val k: @extension Function2<Any, Int, String> = { "" }
+val k: @Extension Function2<Any, Int, String> = { "" }

idea/testData/unifier/equivalence/types/function2.kt.match

@@ -10,4 +10,4 @@ Any.(Int) -> String
 
 (t: Any, u: Int) -> kotlin.String
 
-@extension Function2<Any, Int, String>
+@Extension Function2<Any, Int, String>