DFA: count null comparison as identity comparison #KT-16538 Fixed

+ minor parameter refactoring

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/smartcasts/DataFlowInfo.kt

@@ -73,9 +73,8 @@ interface DataFlowInfo {
 
     /**
      * Call this function when it's known than a == b.
-     * sameTypes should be true iff we have guarantee that a and b have the same type
      */
-    fun equate(a: DataFlowValue, b: DataFlowValue, sameTypes: Boolean, languageVersionSettings: LanguageVersionSettings): DataFlowInfo
+    fun equate(a: DataFlowValue, b: DataFlowValue, identityEquals: Boolean, languageVersionSettings: LanguageVersionSettings): DataFlowInfo
 
     /**
      * Call this function when it's known than a != b

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/smartcasts/DelegatingDataFlowInfo.kt

@@ -169,7 +169,7 @@ internal class DelegatingDataFlowInfo private constructor(
     }
 
     override fun equate(
-            a: DataFlowValue, b: DataFlowValue, sameTypes: Boolean, languageVersionSettings: LanguageVersionSettings
+            a: DataFlowValue, b: DataFlowValue, identityEquals: Boolean, languageVersionSettings: LanguageVersionSettings
     ): DataFlowInfo {
         val builder = Maps.newHashMap<DataFlowValue, Nullability>()
         val nullabilityOfA = getStableNullability(a)
@@ -180,7 +180,7 @@ internal class DelegatingDataFlowInfo private constructor(
 
         // NB: == has no guarantees of type equality, see KT-11280 for the example
         val newTypeInfo = newTypeInfo()
-        if (sameTypes) {
+        if (identityEquals || !nullabilityOfA.canBeNonNull() || !nullabilityOfB.canBeNonNull()) {
             newTypeInfo.putAll(a, getStableTypes(b, false))
             newTypeInfo.putAll(b, getStableTypes(a, false))
             if (a.type != b.type) {

compiler/frontend/src/org/jetbrains/kotlin/types/expressions/DataFlowAnalyzer.java

@@ -178,10 +178,11 @@ public class DataFlowAnalyzer {
                     }
                     if (equals != null) {
                         if (equals == conditionValue) { // this means: equals && conditionValue || !equals && !conditionValue
-                            boolean byIdentity = operationToken == KtTokens.EQEQEQ || operationToken == KtTokens.EXCLEQEQEQ ||
-                                                 typeHasEqualsFromAny(lhsType, condition);
+                            boolean identityEquals = operationToken == KtTokens.EQEQEQ ||
+                                                     operationToken == KtTokens.EXCLEQEQEQ ||
+                                                     typeHasEqualsFromAny(lhsType, condition);
                             result.set(context.dataFlowInfo
-                                               .equate(leftValue, rightValue, byIdentity, languageVersionSettings)
+                                               .equate(leftValue, rightValue, identityEquals, languageVersionSettings)
                                                .and(expressionFlowInfo));
                         }
                         else {

compiler/frontend/src/org/jetbrains/kotlin/types/expressions/PatternMatchingTypingVisitor.kt

@@ -407,8 +407,8 @@ class PatternMatchingTypingVisitor internal constructor(facade: ExpressionTyping
         val result = noChange(newContext)
         return ConditionalDataFlowInfo(
                 result.thenInfo.equate(subjectDataFlowValue, expressionDataFlowValue,
-                                       DataFlowAnalyzer.typeHasEqualsFromAny(subjectType, expression),
-                                       components.languageVersionSettings),
+                                       identityEquals = DataFlowAnalyzer.typeHasEqualsFromAny(subjectType, expression),
+                                       languageVersionSettings = components.languageVersionSettings),
                 result.elseInfo.disequate(subjectDataFlowValue,
                                           expressionDataFlowValue,
                                           components.languageVersionSettings)

compiler/testData/diagnostics/tests/smartCasts/equals.kt

@@ -0,0 +1,25 @@
+fun foo(x: String?) = x
+
+class Test
+
+class TestWithEquals {
+    override fun equals(other: Any?) = super.equals(other)
+}
+
+fun bar(i: Test?) {
+    if (i == null) foo(<!DEBUG_INFO_CONSTANT!>i<!>)
+}
+
+fun bar(i: TestWithEquals?) {
+    if (i == null) foo(<!DEBUG_INFO_CONSTANT!>i<!>)
+    if (null == i) foo(<!DEBUG_INFO_CONSTANT!>i<!>)
+    when (i) {
+        null -> foo(<!DEBUG_INFO_CONSTANT!>i<!>)
+    }
+}
+
+fun gav(i: TestWithEquals?, j: TestWithEquals?) {
+    if (j == null) {
+        if (i == <!DEBUG_INFO_CONSTANT!>j<!>) foo(<!DEBUG_INFO_CONSTANT!>i<!>)
+    }
+}

compiler/testData/diagnostics/tests/smartCasts/equals.txt

@@ -0,0 +1,20 @@
+package
+
+public fun bar(/*0*/ i: Test?): kotlin.Unit
+public fun bar(/*0*/ i: TestWithEquals?): kotlin.Unit
+public fun foo(/*0*/ x: kotlin.String?): kotlin.String?
+public fun gav(/*0*/ i: TestWithEquals?, /*1*/ j: TestWithEquals?): kotlin.Unit
+
+public final class Test {
+    public constructor Test()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}
+
+public final class TestWithEquals {
+    public constructor TestWithEquals()
+    public open override /*1*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

compiler/tests/org/jetbrains/kotlin/checkers/DiagnosticsTestGenerated.java

@@ -19132,6 +19132,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("equals.kt")
+            public void testEquals() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/smartCasts/equals.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("exclUnderAnd.kt")
             public void testExclUnderAnd() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/smartCasts/exclUnderAnd.kt");