KT-7756 Completion of "return null", "return true" and "return false"

#KT-7756 Fixed

idea/idea-completion/src/org/jetbrains/kotlin/idea/completion/CompletionUtils.kt

@@ -28,9 +28,7 @@ import org.jetbrains.kotlin.descriptors.*
 import org.jetbrains.kotlin.idea.caches.resolve.ResolutionFacade
 import org.jetbrains.kotlin.idea.completion.handlers.CastReceiverInsertHandler
 import org.jetbrains.kotlin.idea.completion.handlers.WithTailInsertHandler
-import org.jetbrains.kotlin.idea.util.FuzzyType
+import org.jetbrains.kotlin.idea.util.*
-import org.jetbrains.kotlin.idea.util.findLabelAndCall
-import org.jetbrains.kotlin.idea.util.getImplicitReceiversWithInstanceToExpression
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.psi.*
 import org.jetbrains.kotlin.psi.psiUtil.parents
@@ -41,6 +39,7 @@ import org.jetbrains.kotlin.resolve.BindingContext
 import org.jetbrains.kotlin.resolve.DescriptorToSourceUtils
 import org.jetbrains.kotlin.resolve.DescriptorUtils
 import org.jetbrains.kotlin.resolve.inline.InlineUtil
+import org.jetbrains.kotlin.types.JetType
 import org.jetbrains.kotlin.types.TypeConstructor
 import org.jetbrains.kotlin.types.checker.JetTypeChecker
 import org.jetbrains.kotlin.types.typeUtil.equalTypesOrNulls
@@ -223,11 +222,12 @@ fun returnExpressionItems(bindingContext: BindingContext, position: JetElement):
     val result = ArrayList<LookupElement>()
     for (parent in position.parentsWithSelf) {
         if (parent is JetDeclarationWithBody) {
-            val returnsUnit = returnsUnit(parent, bindingContext)
+            val returnType = parent.returnType(bindingContext)
+            val isUnit = returnType == null || KotlinBuiltIns.isUnit(returnType)
             if (parent is JetFunctionLiteral) {
                 val (label, call) = parent.findLabelAndCall()
                 if (label != null) {
-                    result.add(createKeywordWithLabelElement("return", label, addSpace = !returnsUnit))
+                    result.add(createKeywordWithLabelElement("return", label, addSpace = !isUnit))
                 }
 
                 // check if the current function literal is inlined and stop processing outer declarations if it's not
@@ -236,7 +236,15 @@ fun returnExpressionItems(bindingContext: BindingContext, position: JetElement):
             }
             else {
                 if (parent.hasBlockBody()) {
-                    result.add(createKeywordWithLabelElement("return", null, addSpace = !returnsUnit))
+                    result.add(createKeywordWithLabelElement("return", null, addSpace = !isUnit))
+
+                    if (returnType != null && returnType.nullability() == TypeNullability.NULLABLE) {
+                        result.add(createKeywordWithLabelElement("return null", null, addSpace = false))
+                    }
+                    if (returnType != null && KotlinBuiltIns.isBoolean(returnType.makeNotNullable())) {
+                        result.add(createKeywordWithLabelElement("return true", null, addSpace = false))
+                        result.add(createKeywordWithLabelElement("return false", null, addSpace = false))
+                    }
                 }
                 break
             }
@@ -245,10 +253,9 @@ fun returnExpressionItems(bindingContext: BindingContext, position: JetElement):
     return result
 }
 
-private fun returnsUnit(declaration: JetDeclarationWithBody, bindingContext: BindingContext): Boolean {
+private fun JetDeclarationWithBody.returnType(bindingContext: BindingContext): JetType? {
-    val callable = bindingContext[BindingContext.DECLARATION_TO_DESCRIPTOR, declaration] as? CallableDescriptor ?: return true
+    val callable = bindingContext[BindingContext.DECLARATION_TO_DESCRIPTOR, this] as? CallableDescriptor ?: return null
-    val returnType = callable.getReturnType() ?: return true
+    return callable.getReturnType()
-    return KotlinBuiltIns.isUnit(returnType)
 }
 
 private fun createKeywordWithLabelElement(keyword: String, label: Name?, addSpace: Boolean): LookupElement {

idea/idea-completion/testData/handlers/keywords/ReturnNull.kt

@@ -0,0 +1,5 @@
+fun foo(): String? {
+    ret<caret>
+}
+
+// ELEMENT: "return null"

idea/idea-completion/testData/handlers/keywords/ReturnNull.kt.after

@@ -0,0 +1,5 @@
+fun foo(): String? {
+    return null<caret>
+}
+
+// ELEMENT: "return null"

idea/idea-completion/testData/keywords/ReturnBoolean.kt

@@ -0,0 +1,9 @@
+fun foo(): Boolean {
+    ret<caret>
+}
+
+// INVOCATION_COUNT: 1
+// EXIST: { lookupString: "return", itemText: "return", tailText: null, attributes: "bold" }
+// EXIST: { lookupString: "return true", itemText: "return true", tailText: null, attributes: "bold" }
+// EXIST: { lookupString: "return false", itemText: "return false", tailText: null, attributes: "bold" }
+// NOTHING_ELSE: true

idea/idea-completion/testData/keywords/ReturnNotNull.kt

@@ -0,0 +1,8 @@
+fun foo(): String {
+    ret<caret>
+}
+
+// INVOCATION_COUNT: 1
+// ABSENT: "return null"
+// ABSENT: "return true"
+// ABSENT: "return false"

idea/idea-completion/testData/keywords/ReturnNull.kt

@@ -0,0 +1,8 @@
+fun foo(): String? {
+    ret<caret>
+}
+
+// INVOCATION_COUNT: 1
+// EXIST: { lookupString: "return", itemText: "return", tailText: null, attributes: "bold" }
+// EXIST: { lookupString: "return null", itemText: "return null", tailText: null, attributes: "bold" }
+// NOTHING_ELSE: true

idea/idea-completion/testData/keywords/ReturnNullableBoolean.kt

@@ -0,0 +1,10 @@
+fun foo(): Boolean? {
+    ret<caret>
+}
+
+// INVOCATION_COUNT: 1
+// EXIST: { lookupString: "return", itemText: "return", tailText: null, attributes: "bold" }
+// EXIST: { lookupString: "return null", itemText: "return null", tailText: null, attributes: "bold" }
+// EXIST: { lookupString: "return true", itemText: "return true", tailText: null, attributes: "bold" }
+// EXIST: { lookupString: "return false", itemText: "return false", tailText: null, attributes: "bold" }
+// NOTHING_ELSE: true

idea/idea-completion/testData/weighers/basic/ReturnBoolean.kt

@@ -0,0 +1,7 @@
+fun foo(): Boolean {
+    ret<caret>
+}
+
+// ORDER: return
+// ORDER: return false
+// ORDER: return true

idea/idea-completion/tests/org/jetbrains/kotlin/idea/completion/test/KeywordCompletionTestGenerated.java

@@ -401,12 +401,36 @@ public class KeywordCompletionTestGenerated extends AbstractKeywordCompletionTes
         doTest(fileName);
     }
 
+    @TestMetadata("ReturnBoolean.kt")
+    public void testReturnBoolean() throws Exception {
+        String fileName = JetTestUtils.navigationMetadata("idea/idea-completion/testData/keywords/ReturnBoolean.kt");
+        doTest(fileName);
+    }
+
     @TestMetadata("ReturnKeywordName.kt")
     public void testReturnKeywordName() throws Exception {
         String fileName = JetTestUtils.navigationMetadata("idea/idea-completion/testData/keywords/ReturnKeywordName.kt");
         doTest(fileName);
     }
 
+    @TestMetadata("ReturnNotNull.kt")
+    public void testReturnNotNull() throws Exception {
+        String fileName = JetTestUtils.navigationMetadata("idea/idea-completion/testData/keywords/ReturnNotNull.kt");
+        doTest(fileName);
+    }
+
+    @TestMetadata("ReturnNull.kt")
+    public void testReturnNull() throws Exception {
+        String fileName = JetTestUtils.navigationMetadata("idea/idea-completion/testData/keywords/ReturnNull.kt");
+        doTest(fileName);
+    }
+
+    @TestMetadata("ReturnNullableBoolean.kt")
+    public void testReturnNullableBoolean() throws Exception {
+        String fileName = JetTestUtils.navigationMetadata("idea/idea-completion/testData/keywords/ReturnNullableBoolean.kt");
+        doTest(fileName);
+    }
+
     @TestMetadata("This.kt")
     public void testThis() throws Exception {
         String fileName = JetTestUtils.navigationMetadata("idea/idea-completion/testData/keywords/This.kt");

idea/idea-completion/tests/org/jetbrains/kotlin/idea/completion/test/handlers/KeywordCompletionHandlerTestGenerated.java

@@ -107,6 +107,12 @@ public class KeywordCompletionHandlerTestGenerated extends AbstractKeywordComple
         doTest(fileName);
     }
 
+    @TestMetadata("ReturnNull.kt")
+    public void testReturnNull() throws Exception {
+        String fileName = JetTestUtils.navigationMetadata("idea/idea-completion/testData/handlers/keywords/ReturnNull.kt");
+        doTest(fileName);
+    }
+
     @TestMetadata("SpaceAfterImport.kt")
     public void testSpaceAfterImport() throws Exception {
         String fileName = JetTestUtils.navigationMetadata("idea/idea-completion/testData/handlers/keywords/SpaceAfterImport.kt");

idea/idea-completion/tests/org/jetbrains/kotlin/idea/completion/test/weighers/BasicCompletionWeigherTestGenerated.java

@@ -124,4 +124,10 @@ public class BasicCompletionWeigherTestGenerated extends AbstractBasicCompletion
         String fileName = JetTestUtils.navigationMetadata("idea/idea-completion/testData/weighers/basic/PropertiesBeforeKeywords.kt");
         doTest(fileName);
     }
+
+    @TestMetadata("ReturnBoolean.kt")
+    public void testReturnBoolean() throws Exception {
+        String fileName = JetTestUtils.navigationMetadata("idea/idea-completion/testData/weighers/basic/ReturnBoolean.kt");
+        doTest(fileName);
+    }
 }