Don't suggest cast when !! is possible #KT-18033 Fixed

idea/src/org/jetbrains/kotlin/idea/quickfix/CastExpressionFix.kt

@@ -32,6 +32,7 @@ import org.jetbrains.kotlin.resolve.lazy.BodyResolveMode
 import org.jetbrains.kotlin.types.KotlinType
 import org.jetbrains.kotlin.types.asFlexibleType
 import org.jetbrains.kotlin.types.typeUtil.isSubtypeOf
+import org.jetbrains.kotlin.types.typeUtil.makeNullable
 
 class CastExpressionFix(element: KtExpression, type: KotlinType) : KotlinQuickFixAction<KtExpression>(element) {
     private val typeSourceCode = IdeDescriptorRenderers.SOURCE_CODE.renderType(type)
@@ -39,6 +40,7 @@ class CastExpressionFix(element: KtExpression, type: KotlinType) : KotlinQuickFi
     private val upOrDownCast: Boolean = run {
         val expressionType = element.analyze(BodyResolveMode.PARTIAL).getType(element)
         expressionType != null && (type.isSubtypeOf(expressionType) || expressionType.isSubtypeOf(type))
+        && expressionType != type.makeNullable() //covered by AddExclExclCallFix
     }
 
     override fun getFamilyName() = "Cast expression"

idea/testData/quickfix/typeMismatch/casts/preferExclExcl.kt

@@ -0,0 +1,15 @@
+// "Cast expression 's' to 'String'" "false"
+// ACTION: Add 'toString()' call
+// ACTION: Add non-null asserted (!!) call
+// ACTION: Change parameter 's' type of function 'bar' to 'String?'
+// ACTION: Convert to expression body
+// ACTION: Create function 'bar'
+// ACTION: Surround with null check
+// ACTION: Wrap with '?.let { ... }' call
+// ERROR: Type mismatch: inferred type is String? but String was expected
+
+fun foo(s: String?) {
+    bar(<caret>s)
+}
+
+fun bar(s: String){}

idea/tests/org/jetbrains/kotlin/idea/quickfix/QuickFixTestGenerated.java

@@ -10291,6 +10291,12 @@ public class QuickFixTestGenerated extends AbstractQuickFixTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("preferExclExcl.kt")
+            public void testPreferExclExcl() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("idea/testData/quickfix/typeMismatch/casts/preferExclExcl.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("smartcastImpossible1.kt")
             public void testSmartcastImpossible1() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("idea/testData/quickfix/typeMismatch/casts/smartcastImpossible1.kt");