Add "Change to val" quick fix for MUST_BE_INITIALIZED

#KT-15723 Fixed

idea/src/org/jetbrains/kotlin/idea/quickfix/ChangeVariableMutabilityFix.kt

@@ -128,5 +128,15 @@ class ChangeVariableMutabilityFix(
                 return ChangeVariableMutabilityFix(property, makeVar = false, actionText = "Change to val")
             }
         }
+
+        val MUST_BE_INITIALIZED_FACTORY = object : KotlinSingleIntentionActionFactory() {
+            override fun createAction(diagnostic: Diagnostic): IntentionAction? {
+                val property = Errors.MUST_BE_INITIALIZED.cast(diagnostic).psiElement as? KtProperty ?: return null
+                val getter = property.getter ?: return null
+                if (!getter.hasBody()) return null
+                if (getter.hasBlockBody() && property.typeReference == null) return null
+                return ChangeVariableMutabilityFix(property, makeVar = false)
+            }
+        }
     }
 }

idea/src/org/jetbrains/kotlin/idea/quickfix/QuickFixRegistrar.kt

@@ -639,5 +639,6 @@ class QuickFixRegistrar : QuickFixContributor {
 
         ACCIDENTAL_OVERRIDE.registerFactory(MakePrivateAndOverrideMemberFix.AccidentalOverrideFactory)
 
+        MUST_BE_INITIALIZED.registerFactory(ChangeVariableMutabilityFix.MUST_BE_INITIALIZED_FACTORY)
     }
 }

idea/testData/quickfix/variables/changeMutability/canBeVal/uninitializedWithGetter.kt

@@ -0,0 +1,5 @@
+// "Change to val" "true"
+class Test {
+    var foo<caret>
+        get() = 1
+}

idea/testData/quickfix/variables/changeMutability/canBeVal/uninitializedWithGetter.kt.after

@@ -0,0 +1,5 @@
+// "Change to val" "true"
+class Test {
+    val foo
+        get() = 1
+}

idea/testData/quickfix/variables/changeMutability/canBeVal/uninitializedWithGetter2.kt

@@ -0,0 +1,7 @@
+// "Change to val" "true"
+class Test {
+    var foo: Int<caret>
+        get() {
+            return 1
+        }
+}

idea/testData/quickfix/variables/changeMutability/canBeVal/uninitializedWithGetter2.kt.after

@@ -0,0 +1,7 @@
+// "Change to val" "true"
+class Test {
+    val foo: Int
+        get() {
+            return 1
+        }
+}

idea/testData/quickfix/variables/changeMutability/canBeVal/uninitializedWithGetter3.kt

@@ -0,0 +1,14 @@
+// "Change to val" "false"
+// ACTION: Add initializer
+// ACTION: Convert member to extension
+// ACTION: Initialize with constructor parameter
+// ACTION: Introduce backing property
+// ACTION: Move to companion object
+// ACTION: Specify type explicitly
+// ERROR: Property must be initialized
+class Test {
+    var foo<caret>
+        get() {
+            return 1
+        }
+}

idea/tests/org/jetbrains/kotlin/idea/quickfix/QuickFixTestGenerated.java

@@ -14542,6 +14542,21 @@ public class QuickFixTestGenerated extends AbstractQuickFixTest {
                 public void testSingleVariable() throws Exception {
                     runTest("idea/testData/quickfix/variables/changeMutability/canBeVal/singleVariable.kt");
                 }
+
+                @TestMetadata("uninitializedWithGetter.kt")
+                public void testUninitializedWithGetter() throws Exception {
+                    runTest("idea/testData/quickfix/variables/changeMutability/canBeVal/uninitializedWithGetter.kt");
+                }
+
+                @TestMetadata("uninitializedWithGetter2.kt")
+                public void testUninitializedWithGetter2() throws Exception {
+                    runTest("idea/testData/quickfix/variables/changeMutability/canBeVal/uninitializedWithGetter2.kt");
+                }
+
+                @TestMetadata("uninitializedWithGetter3.kt")
+                public void testUninitializedWithGetter3() throws Exception {
+                    runTest("idea/testData/quickfix/variables/changeMutability/canBeVal/uninitializedWithGetter3.kt");
+                }
             }
         }