FIR: Use Any? expect type to the argument list of ==

^KT-47409 Related

compiler/fir/analysis-tests/legacy-fir-tests/tests-gen/org/jetbrains/kotlin/fir/LazyBodyIsNotTouchedTilContractsPhaseTestGenerated.java

@@ -2421,6 +2421,11 @@ public class LazyBodyIsNotTouchedTilContractsPhaseTestGenerated extends Abstract
             runTest("compiler/fir/analysis-tests/testData/resolve/inference/elvisAndUnit.kt");
         }
 
+        @TestMetadata("equals.kt")
+        public void testEquals() throws Exception {
+            runTest("compiler/fir/analysis-tests/testData/resolve/inference/equals.kt");
+        }
+
         @TestMetadata("extensionCallableReferences.kt")
         public void testExtensionCallableReferences() throws Exception {
             runTest("compiler/fir/analysis-tests/testData/resolve/inference/extensionCallableReferences.kt");

compiler/fir/analysis-tests/testData/resolve/inference/equals.fir.txt

@@ -0,0 +1,18 @@
+FILE: equals.kt
+    public final fun <T> materialize(): R|T| {
+        ^materialize R|kotlin/TODO|()
+    }
+    public final fun main(): R|kotlin/Unit| {
+        when () {
+            ==(String(), R|/materialize|<R|kotlin/Any?|>()) ->  {
+                ^main Unit
+            }
+        }
+
+        when () {
+            ==(R|/materialize|<R|kotlin/Any?|>(), String()) ->  {
+                ^main Unit
+            }
+        }
+
+    }

compiler/fir/analysis-tests/testData/resolve/inference/equals.kt

@@ -0,0 +1,6 @@
+fun <T> materialize(): T = TODO()
+
+fun main() {
+    if ("" == materialize()) return // FE1.0: OK, type argument inferred to Any?
+    if (materialize() == "") return // FE1.0: Error, uninferred type argument for `T`
+}

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirDiagnosticTestGenerated.java

@@ -2751,6 +2751,12 @@ public class FirDiagnosticTestGenerated extends AbstractFirDiagnosticTest {
                 runTest("compiler/fir/analysis-tests/testData/resolve/inference/elvisAndUnit.kt");
             }
 
+            @Test
+            @TestMetadata("equals.kt")
+            public void testEquals() throws Exception {
+                runTest("compiler/fir/analysis-tests/testData/resolve/inference/equals.kt");
+            }
+
             @Test
             @TestMetadata("extensionCallableReferences.kt")
             public void testExtensionCallableReferences() throws Exception {

compiler/fir/analysis-tests/tests-gen/org/jetbrains/kotlin/test/runners/FirDiagnosticsWithLightTreeTestGenerated.java

@@ -2751,6 +2751,12 @@ public class FirDiagnosticsWithLightTreeTestGenerated extends AbstractFirDiagnos
                 runTest("compiler/fir/analysis-tests/testData/resolve/inference/elvisAndUnit.kt");
             }
 
+            @Test
+            @TestMetadata("equals.kt")
+            public void testEquals() throws Exception {
+                runTest("compiler/fir/analysis-tests/testData/resolve/inference/equals.kt");
+            }
+
             @Test
             @TestMetadata("extensionCallableReferences.kt")
             public void testExtensionCallableReferences() throws Exception {

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/body/resolve/FirExpressionsResolveTransformer.kt

@@ -26,12 +26,16 @@ import org.jetbrains.kotlin.fir.resolve.diagnostics.*
 import org.jetbrains.kotlin.fir.resolve.inference.FirStubInferenceSession
 import org.jetbrains.kotlin.fir.resolve.inference.inferenceComponents
 import org.jetbrains.kotlin.fir.resolve.substitution.ConeSubstitutor
-import org.jetbrains.kotlin.fir.resolve.transformers.*
+import org.jetbrains.kotlin.fir.resolve.transformers.InvocationKindTransformer
+import org.jetbrains.kotlin.fir.resolve.transformers.StoreReceiver
+import org.jetbrains.kotlin.fir.resolve.transformers.firClassLike
 import org.jetbrains.kotlin.fir.symbols.impl.FirVariableSymbol
 import org.jetbrains.kotlin.fir.types.*
 import org.jetbrains.kotlin.fir.types.builder.buildErrorTypeRef
 import org.jetbrains.kotlin.fir.types.builder.buildResolvedTypeRef
-import org.jetbrains.kotlin.fir.visitors.*
+import org.jetbrains.kotlin.fir.visitors.FirDefaultTransformer
+import org.jetbrains.kotlin.fir.visitors.TransformData
+import org.jetbrains.kotlin.fir.visitors.transformSingle
 import org.jetbrains.kotlin.name.Name
 import org.jetbrains.kotlin.name.StandardClassIds
 import org.jetbrains.kotlin.resolve.calls.inference.buildAbstractResultingSubstitutor
@@ -490,10 +494,16 @@ open class FirExpressionsResolveTransformer(transformer: FirBodyResolveTransform
         equalityOperatorCall: FirEqualityOperatorCall,
         data: ResolutionMode
     ): FirStatement {
-        val result = (equalityOperatorCall.transformChildren(transformer, ResolutionMode.ContextIndependent) as FirEqualityOperatorCall)
+        // Currently, we use expectedType=Any? for both operands
-            .also { it.resultType = equalityOperatorCall.typeRef.resolvedTypeFromPrototype(builtinTypes.booleanType.type) }
+        // In FE1.0, it's only used for the right
-        dataFlowAnalyzer.exitEqualityOperatorCall(result)
+        // But it seems a bit inconsistent (see KT-47409)
-        return result
+        // Also it's kind of complicated to transform different arguments with different expectType considering current FIR structure
+        equalityOperatorCall.transformAnnotations(transformer, ResolutionMode.ContextIndependent)
+        equalityOperatorCall.argumentList.transformArguments(transformer, withExpectedType(builtinTypes.nullableAnyType))
+        equalityOperatorCall.resultType = equalityOperatorCall.typeRef.resolvedTypeFromPrototype(builtinTypes.booleanType.type)
+
+        dataFlowAnalyzer.exitEqualityOperatorCall(equalityOperatorCall)
+        return equalityOperatorCall
     }
 
     private inline fun <T> resolveCandidateForAssignmentOperatorCall(block: () -> T): T {

compiler/testData/diagnostics/tests/callableReference/resolve/resolveEqualsOperatorWithAnyExpectedType.fir.kt

@@ -1,11 +0,0 @@
-// !LANGUAGE: +NewInference
-
-interface Base
-
-fun <K> materialize(): K = TODO()
-
-fun <T : Base> Base.transform(): T = materialize()
-
-fun test(child: Base) {
-    child == child.<!NEW_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>transform<!>()
-}

compiler/testData/diagnostics/tests/callableReference/resolve/resolveEqualsOperatorWithAnyExpectedType.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !LANGUAGE: +NewInference
 
 interface Base

idea/idea-frontend-fir/idea-fir-low-level-api/tests/org/jetbrains/kotlin/idea/fir/low/level/api/diagnostic/compiler/based/DiagnosisCompilerFirTestdataTestGenerated.java

@@ -2751,6 +2751,12 @@ public class DiagnosisCompilerFirTestdataTestGenerated extends AbstractDiagnosis
                 runTest("compiler/fir/analysis-tests/testData/resolve/inference/elvisAndUnit.kt");
             }
 
+            @Test
+            @TestMetadata("equals.kt")
+            public void testEquals() throws Exception {
+                runTest("compiler/fir/analysis-tests/testData/resolve/inference/equals.kt");
+            }
+
             @Test
             @TestMetadata("extensionCallableReferences.kt")
             public void testExtensionCallableReferences() throws Exception {