Disallow extension properties with backing fields

#KT-1682 Fixed

compiler/testData/diagnostics/tests/enum/extensionNamedAsEnumEntry.kt

@@ -2,7 +2,7 @@ enum class E {
     entry
 }
 
-val Int.entry = 42
-val Long.entry = 239
+val Int.entry: Int get() = 42
+val Long.entry: Int get() = 239
 
 val e = E.entry

compiler/testData/diagnostics/tests/extensions/ExtensionFunctions.kt

@@ -2,7 +2,7 @@
 package outer
 
 fun Int?.optint() : Unit {}
-val Int?.optval : Unit = Unit.VALUE
+val Int?.optval : Unit get() = Unit.VALUE
 
 fun <T: Any, E> T.foo(<!UNUSED_PARAMETER!>x<!> : E, y : A) : T   {
   y.plus(1)

compiler/testData/diagnostics/tests/extensions/kt819ExtensionProperties.kt

@@ -1,4 +1,3 @@
-
 //KT-819 Redeclaration error for extension properties with the same name and different receivers
 
 import java.io.*
@@ -15,16 +14,20 @@ open class A() {
     open fun String.foo() {}
     open fun Int.foo() {}
 
-    open val String.foo = 0
-    open val Int.foo = 1
+    open val String.foo: Int
+        get() = 0
+    open val Int.foo: Int
+        get() = 1
 }
 
 class B() : A() {
     override fun String.foo() {}
     override fun Int.foo() {}
 
-    override val String.foo = 0
-    override val Int.foo = 0
+    override val String.foo: Int
+        get() = 0
+    override val Int.foo: Int
+        get() = 0
 
     fun use(s: String) {
         s.foo

compiler/testData/diagnostics/tests/extensions/object.kt

@@ -1,6 +1,6 @@
 object O
 
 fun Any.foo() = 42
-val Any?.bar = 239
+val Any?.bar: Int get() = 239
 
 val x = O.foo() + O.bar

compiler/testData/diagnostics/tests/overload/kt1998.kt

@@ -10,4 +10,5 @@ object A {
 
 class B
 
-val B.c : String = "test"
+val B.c : String
+    get() = "test"

compiler/testData/diagnostics/tests/redeclarations/ConflictingExtensionProperties.kt

@@ -1,4 +1,4 @@
 package foo
 
-val Int.<!REDECLARATION!>foo<!> = 2
-val Int.<!REDECLARATION!>foo<!> = 3
+val Int.<!REDECLARATION!>foo<!>: Int get() = 2
+val Int.<!REDECLARATION!>foo<!>: Int get() = 3

compiler/testData/diagnostics/tests/regressions/kt1489_1728.kt

@@ -26,5 +26,5 @@ class C {
 
 //KT-1728 Can't invoke extension property as a function
 
-val Int.ext : () -> Int = { 5 }
-val x = 1.ext()
+val Int.ext : () -> Int get() = { 5 }
+val x = 1.ext()

compiler/testData/diagnostics/tests/resolve/invoke/invokeAsExtension.kt

@@ -24,7 +24,8 @@ fun test(a: A) {
 //variable as extension
 trait B {
 }
-val B.foo = Foo()
+val B.foo: Foo
+    get() = Foo()
 
 fun test(b: B) {
     b.foo()

compiler/testData/diagnostics/tests/resolve/invoke/invokeAsMember.kt

@@ -22,7 +22,8 @@ fun test(a: A) {
 
 //variable as extension
 trait B {}
-val B.foo = Foo()
+val B.foo: Foo
+    get() = Foo()
 
 
 fun test(b: B) {

compiler/testData/diagnostics/tests/resolve/invoke/invokeAsMemberExtension.kt

@@ -40,7 +40,8 @@ fun test(c: C, b: B) {
 //variable as extension,
 trait D {
 }
-val D.foo = Foo()
+val D.foo: Foo
+    get() = Foo()
 
 class E {
     fun Foo.invoke() {}

compiler/testData/diagnostics/tests/resolve/invoke/kt3772.kt

@@ -10,10 +10,12 @@ class B {
 }
 
 open class C
-val C.attr = A()
+val C.attr: A
+    get() = A()
 
 open class D: C()
-val D.attr = B()
+val D.attr: B
+    get() = B()
 
 
 fun main(args: Array<String>) {

compiler/testData/diagnostics/tests/scopes/initializerScopeOfExtensionProperty.kt

@@ -1,10 +1,10 @@
 package i
 
-val <T> List<T>.length = <!UNRESOLVED_REFERENCE!>size<!>()
+val <T> List<T>.length = <!EXTENSION_PROPERTY_WITH_BACKING_FIELD!><!UNRESOLVED_REFERENCE!>size<!>()<!>
 
 val <T> List<T>.length1 : Int get() = size()
 
-val String.bd = <!NO_THIS!>this<!> <!DEBUG_INFO_ELEMENT_WITH_ERROR_TYPE!>+<!> "!"
+val String.bd = <!EXTENSION_PROPERTY_WITH_BACKING_FIELD!><!NO_THIS!>this<!> <!DEBUG_INFO_ELEMENT_WITH_ERROR_TYPE!>+<!> "!"<!>
 
 val String.bd1 : String get() = this + "!"
 
@@ -13,7 +13,7 @@ class A {
     val ii : Int = 1
 }
 
-val A.foo = <!UNRESOLVED_REFERENCE!>ii<!>
+val A.foo = <!UNRESOLVED_REFERENCE, EXTENSION_PROPERTY_WITH_BACKING_FIELD!>ii<!>
 
 val A.foo1 : Int get() = ii
 
@@ -22,8 +22,8 @@ class C {
     inner class D {}
 }
 
-val C.foo : C.D = <!UNRESOLVED_REFERENCE!>D<!>()
+val C.foo : C.D = <!EXTENSION_PROPERTY_WITH_BACKING_FIELD!><!UNRESOLVED_REFERENCE!>D<!>()<!>
 
-val C.bar : C.D = C().D()
+val C.bar : C.D = <!EXTENSION_PROPERTY_WITH_BACKING_FIELD!>C().D()<!>
 
-val C.foo1 : C.D get() = D()
+val C.foo1 : C.D get() = D()

compiler/testData/diagnostics/tests/thisAndSuper/thisInPropertyInitializer.kt

@@ -1,7 +1,7 @@
 trait Base {
     fun foo()
 }
-val String.test: Base = object: Base {
+val String.test: Base = <!EXTENSION_PROPERTY_WITH_BACKING_FIELD!>object: Base<!> {
     override fun foo() {
         this<!UNRESOLVED_REFERENCE!>@test<!>
     }