From 6b2da2069d6911a2eb78103402685cdb82829d42 Mon Sep 17 00:00:00 2001
From: "Denis.Zharkov" <denis.zharkov@jetbrains.com>
Date: Fri, 19 May 2023 15:33:42 +0200
Subject: [PATCH] K2: Use Any? expected type only for the right argument of ==
 operator

^KT-47409 Fixed
---
 .../testData/resolve/inference/equals.fir.txt     |  2 +-
 .../testData/resolve/inference/equals.kt          |  3 ++-
 .../resolve/FirExpressionsResolveTransformer.kt   | 15 ++++++++++-----
 3 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/compiler/fir/analysis-tests/testData/resolve/inference/equals.fir.txt b/compiler/fir/analysis-tests/testData/resolve/inference/equals.fir.txt
index cf310f85b6f..80feb1817cd 100644
--- a/compiler/fir/analysis-tests/testData/resolve/inference/equals.fir.txt
+++ b/compiler/fir/analysis-tests/testData/resolve/inference/equals.fir.txt
@@ -10,7 +10,7 @@ FILE: equals.kt
         }
 
         when () {
-            ==(R|/materialize|<R|kotlin/Any?|>(), String()) ->  {
+            ==(R|/materialize<CS errors: /materialize>#|<<ERROR TYPE REF: Cannot infer argument for type parameter T>>(), String()) ->  {
                 ^main Unit
             }
         }
diff --git a/compiler/fir/analysis-tests/testData/resolve/inference/equals.kt b/compiler/fir/analysis-tests/testData/resolve/inference/equals.kt
index 250fad800c4..b9eb12a263b 100644
--- a/compiler/fir/analysis-tests/testData/resolve/inference/equals.kt
+++ b/compiler/fir/analysis-tests/testData/resolve/inference/equals.kt
@@ -1,6 +1,7 @@
+// ISSUE: KT-47409
 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`
+    if (<!NEW_INFERENCE_NO_INFORMATION_FOR_PARAMETER!>materialize<!>() == "") return // FE1.0: Error, uninferred type argument for `T`
 }
diff --git a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/body/resolve/FirExpressionsResolveTransformer.kt b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/body/resolve/FirExpressionsResolveTransformer.kt
index 033dee018ef..f3cceddeff4 100644
--- a/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/body/resolve/FirExpressionsResolveTransformer.kt
+++ b/compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/body/resolve/FirExpressionsResolveTransformer.kt
@@ -804,13 +804,18 @@ open class FirExpressionsResolveTransformer(transformer: FirAbstractBodyResolveT
         equalityOperatorCall: FirEqualityOperatorCall,
         data: ResolutionMode
     ): FirStatement = whileAnalysing(session, equalityOperatorCall) {
-        // Currently, we use expectedType=Any? for both operands
-        // In FE1.0, it's only used for the right
-        // But it seems a bit inconsistent (see KT-47409)
-        // Also it's kind of complicated to transform different arguments with different expectType considering current FIR structure
+        val arguments = equalityOperatorCall.argumentList.arguments
+        require(arguments.size == 2) {
+            "Unexpected number of arguments in equality call: ${arguments.size}"
+        }
+        // In cases like materialize1() == materialize2() we add expected type just for the right argument.
+        // One of the reasons is just consistency with K1 and with the desugared form `a.equals(b)`. See KT-47409 for clarifications.
+        val leftArgumentTransformed: FirExpression = arguments[0].transform(transformer, ResolutionMode.ContextIndependent)
+        val rightArgumentTransformed: FirExpression = arguments[1].transform(transformer, withExpectedType(builtinTypes.nullableAnyType))
+
         equalityOperatorCall
             .transformAnnotations(transformer, ResolutionMode.ContextIndependent)
-            .replaceArgumentList(equalityOperatorCall.argumentList.transform(transformer, withExpectedType(builtinTypes.nullableAnyType)))
+            .replaceArgumentList(buildBinaryArgumentList(leftArgumentTransformed, rightArgumentTransformed))
         equalityOperatorCall.resultType = equalityOperatorCall.typeRef.resolvedTypeFromPrototype(builtinTypes.booleanType.type)
 
         dataFlowAnalyzer.exitEqualityOperatorCall(equalityOperatorCall)