From 1e56815b3ba53c5a572514e4c359196b68d910c8 Mon Sep 17 00:00:00 2001
From: Mikhail Zarechenskiy <mikhail.zarechenskiy@jetbrains.com>
Date: Mon, 3 Apr 2017 02:57:03 +0300
Subject: [PATCH] Do not show warning about useless elvis for error function
 types

 #KT-17214 Fixed
 #KT-12112 Fixed
---
 .../types/expressions/BasicExpressionTypingVisitor.java     | 6 +++++-
 .../diagnostics/tests/nullableTypes/uselessElvis.kt         | 6 +++++-
 .../diagnostics/tests/nullableTypes/uselessElvis.txt        | 1 +
 .../tests/platformTypes/nullabilityWarnings/elvis.kt        | 1 +
 4 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/compiler/frontend/src/org/jetbrains/kotlin/types/expressions/BasicExpressionTypingVisitor.java b/compiler/frontend/src/org/jetbrains/kotlin/types/expressions/BasicExpressionTypingVisitor.java
index 3060c40d25a..a81f9e77a64 100644
--- a/compiler/frontend/src/org/jetbrains/kotlin/types/expressions/BasicExpressionTypingVisitor.java
+++ b/compiler/frontend/src/org/jetbrains/kotlin/types/expressions/BasicExpressionTypingVisitor.java
@@ -892,7 +892,7 @@ public class BasicExpressionTypingVisitor extends ExpressionTypingVisitor {
             return baseTypeInfo;
         }
         DataFlowInfo dataFlowInfo = baseTypeInfo.getDataFlowInfo();
-        if (isKnownToBeNotNull(baseExpression, baseType, context) && (!baseType.isError() || ErrorUtils.isUninferredParameter(baseType))) {
+        if (isKnownToBeNotNull(baseExpression, baseType, context)) {
             context.trace.report(UNNECESSARY_NOT_NULL_ASSERTION.on(operationSign, TypeUtils.makeNotNullable(baseType)));
         }
         else {
@@ -935,12 +935,16 @@ public class BasicExpressionTypingVisitor extends ExpressionTypingVisitor {
         return facade.getTypeInfo(baseExpression, context, isStatement);
     }
 
+    // Returns `true` if warnings should be reported for left-hand side of elvis and not-null (!!) assertion
     private static boolean isKnownToBeNotNull(
             @NotNull KtExpression expression,
             @Nullable KotlinType ktType,
             @NotNull ExpressionTypingContext context
     ) {
         if (ktType == null) return false;
+
+        if (ktType.isError() && !ErrorUtils.isUninferredParameter(ktType)) return false;
+
         if (!TypeUtils.isNullableType(ktType)) return true;
 
         DataFlowValue dataFlowValue = createDataFlowValue(expression, ktType, context);
diff --git a/compiler/testData/diagnostics/tests/nullableTypes/uselessElvis.kt b/compiler/testData/diagnostics/tests/nullableTypes/uselessElvis.kt
index 3898b6e6d18..28985842fc9 100644
--- a/compiler/testData/diagnostics/tests/nullableTypes/uselessElvis.kt
+++ b/compiler/testData/diagnostics/tests/nullableTypes/uselessElvis.kt
@@ -35,10 +35,14 @@ fun test() {
         takeNotNull(dependOn(dependOn(x)) <!USELESS_ELVIS!>?: ""<!>)
         takeNotNull(dependOn(dependOn(x) <!USELESS_CAST!>as? String<!>) ?: "")
     }
+
+    takeNotNull(bar()!!)
 }
 
 inline fun <reified T : Any> reifiedNull(): T? = null
 
 fun testFrom13648() {
     takeNotNull(reifiedNull() ?: "")
-}
\ No newline at end of file
+}
+
+fun bar() = <!UNRESOLVED_REFERENCE!>unresolved<!>
\ No newline at end of file
diff --git a/compiler/testData/diagnostics/tests/nullableTypes/uselessElvis.txt b/compiler/testData/diagnostics/tests/nullableTypes/uselessElvis.txt
index b1c1fd4f2d6..276a19a21b0 100644
--- a/compiler/testData/diagnostics/tests/nullableTypes/uselessElvis.txt
+++ b/compiler/testData/diagnostics/tests/nullableTypes/uselessElvis.txt
@@ -1,5 +1,6 @@
 package
 
+public fun bar(): [ERROR : Error function type]
 public fun </*0*/ T> dependOn(/*0*/ x: T): T
 public fun </*0*/ T> notNull(): T
 public fun </*0*/ T> nullable(): T?
diff --git a/compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/elvis.kt b/compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/elvis.kt
index 468a36456a8..3a0ed4efc32 100644
--- a/compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/elvis.kt
+++ b/compiler/testData/diagnostics/tests/platformTypes/nullabilityWarnings/elvis.kt
@@ -61,6 +61,7 @@ fun test() {
     takeNotNull(J.getNAny() ?: J())
 
     val x = <!UNRESOLVED_REFERENCE!>unresolved<!> ?: null
+    <!UNREACHABLE_CODE!>val y =<!> <!UNRESOLVED_REFERENCE!>unresolved<!>.<!DEBUG_INFO_ELEMENT_WITH_ERROR_TYPE!>foo<!> ?: return
 }
 
 fun takeNotNull(s: J) {}