KT-6118 Redundant type cast can be not redundant?

#KT-6118 Fixed

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/smartcasts/DataFlowValueFactory.java

@@ -78,6 +78,12 @@ public class DataFlowValueFactory {
         }
     }
 
+    @NotNull
+    public static DataFlowValue createDataFlowValue(@NotNull VariableDescriptor variableDescriptor) {
+        JetType type = variableDescriptor.getType();
+        return new DataFlowValue(variableDescriptor, type, isStableVariable(variableDescriptor), getImmanentNullability(type));
+    }
+
     @NotNull
     private static Nullability getImmanentNullability(@NotNull JetType type) {
         return TypeUtils.isNullableType(type) ? Nullability.UNKNOWN : Nullability.NOT_NULL;

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

@@ -22,6 +22,7 @@ import org.jetbrains.annotations.Nullable;
 import org.jetbrains.kotlin.types.JetType;
 import org.jetbrains.kotlin.types.TypeUtils;
 
+import java.util.LinkedHashSet;
 import java.util.Map;
 import java.util.Set;
 
@@ -130,7 +131,39 @@ import static org.jetbrains.kotlin.resolve.calls.smartcasts.Nullability.NOT_NULL
         boolean changed = false;
         changed |= putNullability(builder, a, nullabilityOfA.refine(nullabilityOfB));
         changed |= putNullability(builder, b, nullabilityOfB.refine(nullabilityOfA));
-        return changed ? new DelegatingDataFlowInfo(this, ImmutableMap.copyOf(builder), EMPTY_TYPE_INFO) : this;
+
+        SetMultimap<DataFlowValue, JetType> newTypeInfo = newTypeInfo();
+        newTypeInfo.putAll(a, collectTypesFromMeAndParents(b));
+        newTypeInfo.putAll(b, collectTypesFromMeAndParents(a));
+        changed |= !newTypeInfo.isEmpty();
+
+        return !changed
+                    ? this
+                    : new DelegatingDataFlowInfo(
+                            this,
+                            ImmutableMap.copyOf(builder),
+                            newTypeInfo.isEmpty() ? EMPTY_TYPE_INFO : newTypeInfo
+                    );
+    }
+
+    @NotNull
+    private Set<JetType> collectTypesFromMeAndParents(@NotNull DataFlowValue value) {
+        Set<JetType> types = new LinkedHashSet<JetType>();
+
+        DataFlowInfo current = this;
+        while (current != null) {
+            if (current instanceof DelegatingDataFlowInfo) {
+                DelegatingDataFlowInfo delegatingInfo = (DelegatingDataFlowInfo) current;
+                types.addAll(delegatingInfo.typeInfo.get(value));
+                current = delegatingInfo.parent;
+            }
+            else {
+                types.addAll(current.getPossibleTypes(value));
+                break;
+            }
+        }
+
+        return types;
     }
 
     @Override

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

@@ -38,6 +38,8 @@ import org.jetbrains.kotlin.resolve.calls.model.ResolvedCall;
 import org.jetbrains.kotlin.resolve.calls.results.OverloadResolutionResults;
 import org.jetbrains.kotlin.resolve.calls.results.OverloadResolutionResultsUtil;
 import org.jetbrains.kotlin.resolve.calls.smartcasts.DataFlowInfo;
+import org.jetbrains.kotlin.resolve.calls.smartcasts.DataFlowValue;
+import org.jetbrains.kotlin.resolve.calls.smartcasts.DataFlowValueFactory;
 import org.jetbrains.kotlin.resolve.scopes.JetScope;
 import org.jetbrains.kotlin.resolve.scopes.WritableScope;
 import org.jetbrains.kotlin.resolve.scopes.receivers.ExpressionReceiver;
@@ -135,6 +137,12 @@ public class ExpressionTypingVisitorForStatements extends ExpressionTypingVisito
             JetType outType = propertyDescriptor.getType();
             JetTypeInfo typeInfo = facade.getTypeInfo(initializer, context.replaceExpectedType(outType));
             dataFlowInfo = typeInfo.getDataFlowInfo();
+            JetType type = typeInfo.getType();
+            if (property.getTypeReference() == null && type != null) {
+                DataFlowValue variableDataFlowValue = DataFlowValueFactory.createDataFlowValue(propertyDescriptor);
+                DataFlowValue initializerDataFlowValue = DataFlowValueFactory.createDataFlowValue(initializer, type, context.trace.getBindingContext());
+                dataFlowInfo = dataFlowInfo.equate(variableDataFlowValue, initializerDataFlowValue);
+            }
         }
 
         {
@@ -335,6 +343,12 @@ public class ExpressionTypingVisitorForStatements extends ExpressionTypingVisito
         if (right != null) {
             JetTypeInfo rightInfo = facade.getTypeInfo(right, context.replaceDataFlowInfo(dataFlowInfo).replaceExpectedType(leftType));
             dataFlowInfo = rightInfo.getDataFlowInfo();
+            JetType rightType = rightInfo.getType();
+            if (left != null && leftType != null && rightType != null) {
+                DataFlowValue leftValue = DataFlowValueFactory.createDataFlowValue(left, leftType, context.trace.getBindingContext());
+                DataFlowValue rightValue = DataFlowValueFactory.createDataFlowValue(right, rightType, context.trace.getBindingContext());
+                dataFlowInfo = dataFlowInfo.equate(leftValue, rightValue);
+            }
         }
         if (leftType != null && leftOperand != null) { //if leftType == null, some other error has been generated
             BasicExpressionTypingVisitor.checkLValue(context.trace, leftOperand);

compiler/testData/diagnostics/tests/dataFlow/assignment/assignToNewVal.kt

@@ -0,0 +1,10 @@
+fun test(a: Any?) {
+    if (a == null) return
+    <!DEBUG_INFO_SMARTCAST!>a<!>.hashCode()
+
+    val b = a
+    <!DEBUG_INFO_SMARTCAST!>b<!>.hashCode()
+
+    val c: Any? = a
+    c<!UNSAFE_CALL!>.<!>hashCode()
+}

compiler/testData/diagnostics/tests/dataFlow/assignment/assignToNewVal.txt

@@ -0,0 +1,3 @@
+package
+
+internal fun test(/*0*/ a: kotlin.Any?): kotlin.Unit

compiler/testData/diagnostics/tests/dataFlow/assignment/kt6118.kt

@@ -0,0 +1,16 @@
+// KT-6118 Redundant type cast can be not redundant?
+
+fun foo(o: Any) {
+    if (o is String) {
+        val s = o <!USELESS_CAST_STATIC_ASSERT_IS_FINE!>as String<!>
+        s.length()
+    }
+}
+
+fun foo1(o: Any) {
+    if (o is String) {
+        <!DEBUG_INFO_SMARTCAST!>o<!>.length()
+        val s = o
+        <!DEBUG_INFO_SMARTCAST!>s<!>.length()
+    }
+}

compiler/testData/diagnostics/tests/dataFlow/assignment/kt6118.txt

@@ -0,0 +1,4 @@
+package
+
+internal fun foo(/*0*/ o: kotlin.Any): kotlin.Unit
+internal fun foo1(/*0*/ o: kotlin.Any): kotlin.Unit

compiler/testData/diagnostics/tests/dataFlow/assignment/uninitializedValIsCheck.kt

@@ -0,0 +1,15 @@
+fun test(a: Any?, flag: Boolean, x: Any?) {
+    if (a !is String) return
+    <!DEBUG_INFO_SMARTCAST!>a<!>.length()
+
+    val b: Any?
+
+    if (flag) {
+        b = a
+        <!DEBUG_INFO_SMARTCAST!>b<!>.length()
+    }
+    else {
+        b = x
+        b.<!UNRESOLVED_REFERENCE!>length<!>()
+    }
+}

compiler/testData/diagnostics/tests/dataFlow/assignment/uninitializedValIsCheck.txt

@@ -0,0 +1,3 @@
+package
+
+internal fun test(/*0*/ a: kotlin.Any?, /*1*/ flag: kotlin.Boolean, /*2*/ x: kotlin.Any?): kotlin.Unit

compiler/testData/diagnostics/tests/dataFlow/assignment/uninitializedValNullability.kt

@@ -0,0 +1,15 @@
+fun test(a: Any?, flag: Boolean, x: Any?) {
+    if (a == null) return
+    <!DEBUG_INFO_SMARTCAST!>a<!>.hashCode()
+
+    val b: Any?
+
+    if (flag) {
+        b = a
+        <!DEBUG_INFO_SMARTCAST!>b<!>.hashCode()
+    }
+    else {
+        b = x
+        b<!UNSAFE_CALL!>.<!>hashCode()
+    }
+}

compiler/testData/diagnostics/tests/dataFlow/assignment/uninitializedValNullability.txt

@@ -0,0 +1,3 @@
+package
+
+internal fun test(/*0*/ a: kotlin.Any?, /*1*/ flag: kotlin.Boolean, /*2*/ x: kotlin.Any?): kotlin.Unit

compiler/testData/diagnostics/tests/dataFlow/assignment/when.kt

@@ -0,0 +1,12 @@
+fun test(a: Any?) {
+    when (a) {
+        is String -> {
+            val s = a
+            <!DEBUG_INFO_SMARTCAST!>s<!>.length()
+        }
+        "" -> {
+            val s = a
+            <!DEBUG_INFO_SMARTCAST!>s<!>.hashCode()
+        }
+    }
+}

compiler/testData/diagnostics/tests/dataFlow/assignment/when.txt

@@ -0,0 +1,3 @@
+package
+
+internal fun test(/*0*/ a: kotlin.Any?): kotlin.Unit

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

@@ -2277,7 +2277,7 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
 
         @TestMetadata("compiler/testData/diagnostics/tests/dataFlow")
         @TestDataPath("$PROJECT_ROOT")
-        @InnerTestClasses({DataFlow.Local.class})
+        @InnerTestClasses({DataFlow.Assignment.class, DataFlow.Local.class})
         @RunWith(JUnit3RunnerWithInners.class)
         public static class DataFlow extends AbstractJetDiagnosticsTest {
             public void testAllFilesPresentInDataFlow() throws Exception {
@@ -2308,6 +2308,45 @@ public class JetDiagnosticsTestGenerated extends AbstractJetDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("compiler/testData/diagnostics/tests/dataFlow/assignment")
+            @TestDataPath("$PROJECT_ROOT")
+            @RunWith(JUnit3RunnerWithInners.class)
+            public static class Assignment extends AbstractJetDiagnosticsTest {
+                public void testAllFilesPresentInAssignment() throws Exception {
+                    JetTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("compiler/testData/diagnostics/tests/dataFlow/assignment"), Pattern.compile("^(.+)\\.kt$"), true);
+                }
+
+                @TestMetadata("assignToNewVal.kt")
+                public void testAssignToNewVal() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/dataFlow/assignment/assignToNewVal.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("kt6118.kt")
+                public void testKt6118() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/dataFlow/assignment/kt6118.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("uninitializedValIsCheck.kt")
+                public void testUninitializedValIsCheck() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/dataFlow/assignment/uninitializedValIsCheck.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("uninitializedValNullability.kt")
+                public void testUninitializedValNullability() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/dataFlow/assignment/uninitializedValNullability.kt");
+                    doTest(fileName);
+                }
+
+                @TestMetadata("when.kt")
+                public void testWhen() throws Exception {
+                    String fileName = JetTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/dataFlow/assignment/when.kt");
+                    doTest(fileName);
+                }
+            }
+
             @TestMetadata("compiler/testData/diagnostics/tests/dataFlow/local")
             @TestDataPath("$PROJECT_ROOT")
             @RunWith(JUnit3RunnerWithInners.class)