[groovy] fix nullability warning (EA-101589, IDEA-178856)

plugins/groovy/src/org/jetbrains/plugins/groovy/intentions/other/GrCopyStringConcatenationContentIntention.java

@@ -23,7 +23,6 @@ import com.intellij.util.IncorrectOperationException;
 import org.jetbrains.annotations.NotNull;
 import org.jetbrains.plugins.groovy.intentions.base.Intention;
 import org.jetbrains.plugins.groovy.intentions.base.PsiElementPredicate;
-import org.jetbrains.plugins.groovy.lang.lexer.GroovyTokenTypes;
 import org.jetbrains.plugins.groovy.lang.psi.api.statements.expressions.GrBinaryExpression;
 import org.jetbrains.plugins.groovy.lang.psi.api.statements.expressions.literals.GrLiteral;
 
@@ -56,16 +55,6 @@ public class GrCopyStringConcatenationContentIntention extends Intention {
   @NotNull
   @Override
   protected PsiElementPredicate getElementPredicate() {
-    return new PsiElementPredicate() {
-      @Override
-      public boolean satisfiedBy(@NotNull PsiElement element) {
-        if (element instanceof GrLiteral && ((GrLiteral)element).getValue() instanceof String) return true;
-
-        return element instanceof GrBinaryExpression &&
-               ((GrBinaryExpression)element).getOperationTokenType() == GroovyTokenTypes.mPLUS &&
-               satisfiedBy(((GrBinaryExpression)element).getLeftOperand()) &&
-               satisfiedBy(((GrBinaryExpression)element).getRightOperand());
-      }
-    };
+    return GrCopyStringConcatenationPredicate.INSTANCE;
   }
 }

plugins/groovy/src/org/jetbrains/plugins/groovy/intentions/other/GrCopyStringConcatenationPredicate.kt

@@ -0,0 +1,34 @@
+/*
+ * Copyright 2000-2017 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.jetbrains.plugins.groovy.intentions.other
+
+import com.intellij.psi.PsiElement
+import org.jetbrains.plugins.groovy.intentions.base.PsiElementPredicate
+import org.jetbrains.plugins.groovy.lang.lexer.GroovyTokenTypes
+import org.jetbrains.plugins.groovy.lang.psi.api.statements.expressions.GrBinaryExpression
+import org.jetbrains.plugins.groovy.lang.psi.api.statements.expressions.literals.GrLiteral
+
+object GrCopyStringConcatenationPredicate : PsiElementPredicate {
+
+  override fun satisfiedBy(element: PsiElement): Boolean {
+    if (element is GrLiteral && element.value is String) return true
+    if (element !is GrBinaryExpression) return false
+    if (element.operationTokenType !== GroovyTokenTypes.mPLUS) return false
+    val left = element.leftOperand
+    val right = element.rightOperand ?: return false
+    return satisfiedBy(left) && satisfiedBy(right)
+  }
+}