J2K: generate accessor bodies in expression form if possible

idea/src/org/jetbrains/kotlin/idea/intentions/ConvertToExpressionBodyIntention.kt

@@ -114,7 +114,7 @@ public class ConvertToExpressionBodyIntention : JetSelfTargetingOffsetIndependen
             is JetDeclaration, is JetLoopExpression -> return null // is JetExpression but does not have value
 
             else  -> {
-                if (statement is JetBinaryExpression && statement.getOperationToken() == JetTokens.EQ) return null // assignment does not have value
+                if (statement is JetBinaryExpression && statement.operationToken in JetTokens.ALL_ASSIGNMENTS) return null // assignment does not have value
                 val expressionType = statement.analyze().getType(statement) ?: return null
                 if (!KotlinBuiltIns.isUnit(expressionType) && !KotlinBuiltIns.isNothing(expressionType)) return null
                 return statement

idea/src/org/jetbrains/kotlin/idea/j2k/J2kPostProcessings.kt

@@ -52,6 +52,7 @@ object J2KPostProcessingRegistrar {
         _processings.add(ConvertToStringTemplateProcessing())
         _processings.add(UsePropertyAccessSyntaxProcessing())
         _processings.add(RemoveRedundantSamAdaptersProcessing())
+        _processings.add(AccessorBodyToExpression())
 
         registerIntentionBasedProcessing(IfThenToSafeAccessIntention()) { applyTo(it) }
         registerIntentionBasedProcessing(IfThenToElvisIntention()) { applyTo(it) }
@@ -192,4 +193,14 @@ object J2KPostProcessingRegistrar {
             }
         }
     }
+
+    private class AccessorBodyToExpression : J2kPostProcessing {
+        private val intention = ConvertToExpressionBodyIntention()
+
+        override fun createAction(element: JetElement, diagnostics: Diagnostics): (() -> Unit)? {
+            if (element !is JetPropertyAccessor) return null
+            if (!intention.isApplicableTo(element)) return null
+            return { intention.applyTo(element, true) }
+        }
+    }
 }

idea/testData/intentions/convertToExpressionBody/assignPlus.kt

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

idea/tests/org/jetbrains/kotlin/idea/intentions/IntentionTestGenerated.java

@@ -4027,6 +4027,12 @@ public class IntentionTestGenerated extends AbstractIntentionTest {
             doTest(fileName);
         }
 
+        @TestMetadata("assignPlus.kt")
+        public void testAssignPlus() throws Exception {
+            String fileName = JetTestUtils.navigationMetadata("idea/testData/intentions/convertToExpressionBody/assignPlus.kt");
+            doTest(fileName);
+        }
+
         @TestMetadata("assignment.kt")
         public void testAssignment() throws Exception {
             String fileName = JetTestUtils.navigationMetadata("idea/testData/intentions/convertToExpressionBody/assignment.kt");