For-loop now cannot use extension iterator on a nullable #KT-7428 Fixed

compiler/frontend/src/org/jetbrains/kotlin/resolve/BindingContextUtils.java

@@ -25,6 +25,7 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.kotlin.descriptors.*;
 import org.jetbrains.kotlin.diagnostics.Diagnostic;
+import org.jetbrains.kotlin.diagnostics.Severity;
 import org.jetbrains.kotlin.psi.*;
 import org.jetbrains.kotlin.resolve.calls.callUtil.CallUtilKt;
 import org.jetbrains.kotlin.resolve.calls.model.ResolvedCall;
@@ -35,11 +36,11 @@ import org.jetbrains.kotlin.types.KotlinType;
 import org.jetbrains.kotlin.types.TypeUtils;
 import org.jetbrains.kotlin.types.expressions.KotlinTypeInfo;
 import org.jetbrains.kotlin.types.expressions.typeInfoFactory.TypeInfoFactoryKt;
-import org.jetbrains.kotlin.util.slicedMap.MutableSlicedMap;
-import org.jetbrains.kotlin.util.slicedMap.ReadOnlySlice;
-import org.jetbrains.kotlin.util.slicedMap.WritableSlice;
+import org.jetbrains.kotlin.util.slicedMap.*;
 
 import java.util.Collection;
+import java.util.EnumMap;
+import java.util.Map;
 
 import static org.jetbrains.kotlin.diagnostics.Errors.AMBIGUOUS_LABEL;
 import static org.jetbrains.kotlin.resolve.BindingContext.*;
@@ -222,7 +223,7 @@ public class BindingContextUtils {
         map.forEach(new Function3<WritableSlice, Object, Object, Void>() {
             @Override
             public Void invoke(WritableSlice slice, Object key, Object value) {
-                if (filter == null || filter.accept(slice, key)) {
+                if (filter == null || filter.accept(slice, null, key)) {
                     trace.record(slice, key, value);
                 }
 
@@ -233,7 +234,7 @@ public class BindingContextUtils {
         if (!commitDiagnostics) return;
 
         for (Diagnostic diagnostic : diagnostics.getOwnDiagnostics()) {
-            if (filter == null || filter.accept(null, diagnostic.getPsiElement())) {
+            if (filter == null || filter.accept(null, diagnostic, diagnostic.getPsiElement())) {
                 trace.report(diagnostic);
             }
         }

compiler/frontend/src/org/jetbrains/kotlin/resolve/DelegatedPropertyResolver.java

@@ -23,6 +23,7 @@ import org.jetbrains.annotations.NotNull;
 import org.jetbrains.annotations.Nullable;
 import org.jetbrains.kotlin.builtins.KotlinBuiltIns;
 import org.jetbrains.kotlin.descriptors.*;
+import org.jetbrains.kotlin.diagnostics.Diagnostic;
 import org.jetbrains.kotlin.diagnostics.rendering.Renderers;
 import org.jetbrains.kotlin.name.Name;
 import org.jetbrains.kotlin.psi.*;
@@ -333,7 +334,7 @@ public class DelegatedPropertyResolver {
                                                                        dataFlowInfo, traceToResolveDelegatedProperty);
         traceToResolveDelegatedProperty.commit(new TraceEntryFilter() {
             @Override
-            public boolean accept(@Nullable WritableSlice<?, ?> slice, Object key) {
+            public boolean accept(@Nullable WritableSlice<?, ?> slice, @Nullable Diagnostic diagnostic, Object key) {
                 return slice != CONSTRAINT_SYSTEM_COMPLETER;
             }
         }, true);

compiler/frontend/src/org/jetbrains/kotlin/resolve/TraceEntryFilter.java

@@ -17,8 +17,9 @@
 package org.jetbrains.kotlin.resolve;
 
 import org.jetbrains.annotations.Nullable;
+import org.jetbrains.kotlin.diagnostics.Diagnostic;
 import org.jetbrains.kotlin.util.slicedMap.WritableSlice;
 
 public interface TraceEntryFilter {
-    boolean accept(@Nullable WritableSlice<?, ?> slice, Object key);
+    boolean accept(@Nullable WritableSlice<?, ?> slice, @Nullable Diagnostic diagnostic, Object key);
 }

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

@@ -1178,7 +1178,7 @@ public class BasicExpressionTypingVisitor extends ExpressionTypingVisitor {
 
         traceInterpretingRightAsNullableAny.commit(new TraceEntryFilter() {
             @Override
-            public boolean accept(@Nullable WritableSlice<?, ?> slice, Object key) {
+            public boolean accept(@Nullable WritableSlice<?, ?> slice, @Nullable Diagnostic diagnostic, Object key) {
                 // the type of the right (and sometimes left) expression isn't 'Any?' actually
                 if ((key == right || key == left) && slice == EXPRESSION_TYPE_INFO) return false;
 

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

@@ -18,11 +18,14 @@ package org.jetbrains.kotlin.types.expressions
 
 import com.intellij.openapi.project.Project
 import org.jetbrains.kotlin.descriptors.FunctionDescriptor
+import org.jetbrains.kotlin.diagnostics.Errors
+import org.jetbrains.kotlin.diagnostics.Severity
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.psi.Call
 import org.jetbrains.kotlin.psi.KtExpression
 import org.jetbrains.kotlin.psi.KtPsiFactory
 import org.jetbrains.kotlin.psi.KtSimpleNameExpression
+import org.jetbrains.kotlin.resolve.BindingContextUtils
 import org.jetbrains.kotlin.resolve.TemporaryBindingTrace
 import org.jetbrains.kotlin.resolve.calls.CallResolver
 import org.jetbrains.kotlin.resolve.calls.results.OverloadResolutionResults
@@ -75,17 +78,28 @@ class FakeCallResolver(
             context: ExpressionTypingContext,
             valueArguments: List<KtExpression>,
             name: Name,
-            callElement: KtExpression?
+            callElement: KtExpression?,
+            iteratorCheck: Boolean = false
     ): Pair<Call, OverloadResolutionResults<FunctionDescriptor>> {
         val fakeTrace = TemporaryBindingTrace.create(context.trace, "trace to resolve fake call for", name)
         val fakeBindingTrace = context.replaceBindingTrace(fakeTrace)
 
-        return makeAndResolveFakeCallInContext(receiver, fakeBindingTrace, valueArguments, name, callElement) { fake ->
-            fakeTrace.commit({ slice, key ->
+        var hasUnreportedIteratorError = false
+        val result = makeAndResolveFakeCallInContext(receiver, fakeBindingTrace, valueArguments, name, callElement) { fake ->
+            fakeTrace.commit({ slice, diagnostic, key ->
                 // excluding all entries related to fake expression
-                key != fake
+                // convert all errors on this expression to ITERATOR_MISSING on callElement
+                val isFakeKey = key == fake
+                if (iteratorCheck && diagnostic?.severity == Severity.ERROR && isFakeKey) {
+                    hasUnreportedIteratorError = true
+                }
+                !isFakeKey
             }, true)
         }
+        if (hasUnreportedIteratorError && callElement != null) {
+            context.trace.report(Errors.ITERATOR_MISSING.on(callElement))
+        }
+        return result
     }
 
     @JvmOverloads fun makeAndResolveFakeCallInContext(

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

@@ -67,7 +67,7 @@ public class ForLoopConventionsChecker {
         Name iterator = Name.identifier("iterator");
         Pair<Call, OverloadResolutionResults<FunctionDescriptor>> calls =
                 fakeCallResolver.makeAndResolveFakeCall(loopRange, context, Collections.<KtExpression>emptyList(), iterator,
-                                                        loopRange.getExpression());
+                                                        loopRange.getExpression(), true);
         OverloadResolutionResults<FunctionDescriptor> iteratorResolutionResults = calls.getSecond();
 
         if (iteratorResolutionResults.isSuccess()) {

compiler/testData/diagnostics/tests/controlStructures/ForLoopWithExtensionIteratorOnNullable.kt

@@ -0,0 +1,21 @@
+// See also KT-7428
+class Container<K>(val k: K)
+// iterator() must be an extension, otherwise code will not compile
+operator fun <K> Container<K>.iterator(): Iterator<K> = null!!
+
+fun test() {
+    val container: Container<String>? = null
+    // Error
+    container<!UNSAFE_CALL!>.<!>iterator()
+    // for extension iterator, this code compiles, but should not
+    for (s in <!ITERATOR_MISSING!>container<!>) {}
+}
+class OtherContainer<K>(val k: K) {
+    operator fun iterator(): Iterator<K> = null!!
+}
+
+fun test2() {
+    val other: OtherContainer<String>? = null
+    // Error
+    for (s in <!ITERATOR_MISSING!>other<!>) {}
+}

compiler/testData/diagnostics/tests/controlStructures/ForLoopWithExtensionIteratorOnNullable.txt

@@ -0,0 +1,22 @@
+package
+
+public fun test(): kotlin.Unit
+public fun test2(): kotlin.Unit
+public operator fun </*0*/ K> Container<K>.iterator(): kotlin.collections.Iterator<K>
+
+public final class Container</*0*/ K> {
+    public constructor Container</*0*/ K>(/*0*/ k: K)
+    public final val k: K
+    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 OtherContainer</*0*/ K> {
+    public constructor OtherContainer</*0*/ K>(/*0*/ k: K)
+    public final val k: K
+    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 final operator fun iterator(): kotlin.collections.Iterator<K>
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}

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

@@ -3330,6 +3330,12 @@ public class DiagnosticsTestGenerated extends AbstractDiagnosticsTest {
                 doTest(fileName);
             }
 
+            @TestMetadata("ForLoopWithExtensionIteratorOnNullable.kt")
+            public void testForLoopWithExtensionIteratorOnNullable() throws Exception {
+                String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/controlStructures/ForLoopWithExtensionIteratorOnNullable.kt");
+                doTest(fileName);
+            }
+
             @TestMetadata("forLoopWithNullableRange.kt")
             public void testForLoopWithNullableRange() throws Exception {
                 String fileName = KotlinTestUtils.navigationMetadata("compiler/testData/diagnostics/tests/controlStructures/forLoopWithNullableRange.kt");