New Intention Action: Replace with operator assign

Replaces a statement of the form a = a + b with a statement of the form
a += b.

idea/testData/intentions/replaceWithOperatorAssign/illegalMultipleOperators.kt

@@ -0,0 +1,5 @@
+// IS_APPLICABLE: false
+fun foo() {
+    var x = 0
+    x = x / 1 + 1
+}

idea/testData/intentions/replaceWithOperatorAssign/illegalMultipleOperatorsMiddle.kt

@@ -0,0 +1,6 @@
+// IS_APPLICABLE: false
+fun foo() {
+    var x = 0
+    val y = 0
+    x = y / x + 0
+}

idea/testData/intentions/replaceWithOperatorAssign/invalidSubtraction.kt

@@ -0,0 +1,5 @@
+// IS_APPLICABLE: false
+fun foo() {
+    var x = 0
+    <caret>x = 1 - x
+}

idea/testData/intentions/replaceWithOperatorAssign/multipleOperators.kt

@@ -0,0 +1,5 @@
+fun foo() {
+    var x = 0
+    var y = 0
+    <caret>x = x + y + 5
+}

idea/testData/intentions/replaceWithOperatorAssign/multipleOperators.kt.after

@@ -0,0 +1,5 @@
+fun foo() {
+    var x = 0
+    var y = 0
+    x += y + 5
+}

idea/testData/intentions/replaceWithOperatorAssign/multipleOperatorsRightSideRepeat.kt

@@ -0,0 +1,5 @@
+fun foo() {
+    var x = 0
+    var y = 0
+    <caret>x = y + x + 5
+}

idea/testData/intentions/replaceWithOperatorAssign/multipleOperatorsRightSideRepeat.kt.after

@@ -0,0 +1,5 @@
+fun foo() {
+    var x = 0
+    var y = 0
+    x += y + 5
+}

idea/testData/intentions/replaceWithOperatorAssign/nonRepeatingAssignment.kt

@@ -0,0 +1,7 @@
+// IS_APPLICABLE: false
+fun foo() {
+    var x = 0
+    val y = 0
+    val z = 0
+    <caret>x = y + z
+}

idea/testData/intentions/replaceWithOperatorAssign/rightSideRepeat.kt

@@ -0,0 +1,4 @@
+fun foo() {
+    var x = 0
+    <caret>x = 1 + x
+}

idea/testData/intentions/replaceWithOperatorAssign/rightSideRepeat.kt.after

@@ -0,0 +1,4 @@
+fun foo() {
+    var x = 0
+    x += 1
+}

idea/testData/intentions/replaceWithOperatorAssign/simpleAssign.kt

@@ -0,0 +1,5 @@
+fun foo() {
+    var y = 0
+    val x = 0
+    <caret>y = y + x
+}

idea/testData/intentions/replaceWithOperatorAssign/simpleAssign.kt.after

@@ -0,0 +1,5 @@
+fun foo() {
+    var y = 0
+    val x = 0
+    y += x
+}

idea/testData/intentions/replaceWithOperatorAssign/validSubtraction.kt

@@ -0,0 +1,4 @@
+fun foo() {
+    var x = 0
+    <caret>x = x - 1
+}

idea/testData/intentions/replaceWithOperatorAssign/validSubtraction.kt.after

@@ -0,0 +1,4 @@
+fun foo() {
+    var x = 0
+    x -= 1
+}