[FIR] Allow nullable receiver type in case of safe-calls

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/Arguments.kt

@@ -32,6 +32,7 @@ fun resolveArgumentExpression(
     expectedTypeRef: FirTypeRef,
     sink: CheckerSink,
     isReceiver: Boolean,
+    isSafeCall: Boolean,
     acceptLambdaAtoms: (PostponedResolvedAtomMarker) -> Unit,
     typeProvider: (FirExpression) -> FirTypeRef?
 ) {
@@ -42,6 +43,7 @@ fun resolveArgumentExpression(
             expectedType,
             sink,
             isReceiver,
+            isSafeCall,
             typeProvider
         )
         // TODO:!
@@ -57,6 +59,7 @@ fun resolveArgumentExpression(
             expectedTypeRef,
             sink,
             isReceiver,
+            isSafeCall,
             acceptLambdaAtoms,
             typeProvider
         )
@@ -67,10 +70,11 @@ fun resolveArgumentExpression(
             expectedTypeRef,
             sink,
             isReceiver,
+            isSafeCall,
             acceptLambdaAtoms,
             typeProvider
         )
-        else -> resolvePlainExpressionArgument(csBuilder, argument, expectedType, sink, isReceiver, typeProvider)
+        else -> resolvePlainExpressionArgument(csBuilder, argument, expectedType, sink, isReceiver, isSafeCall, typeProvider)
     }
 }
 
@@ -80,11 +84,12 @@ fun resolvePlainExpressionArgument(
     expectedType: ConeKotlinType?,
     sink: CheckerSink,
     isReceiver: Boolean,
+    isSafeCall: Boolean,
     typeProvider: (FirExpression) -> FirTypeRef?
 ) {
     if (expectedType == null) return
     val argumentType = typeProvider(argument)?.coneTypeSafe<ConeKotlinType>() ?: return
-    resolvePlainArgumentType(csBuilder, argumentType, expectedType, sink, isReceiver)
+    resolvePlainArgumentType(csBuilder, argumentType, expectedType, sink, isReceiver, isSafeCall)
 }
 
 fun resolvePlainArgumentType(
@@ -92,12 +97,20 @@ fun resolvePlainArgumentType(
     argumentType: ConeKotlinType,
     expectedType: ConeKotlinType,
     sink: CheckerSink,
-    isReceiver: Boolean
+    isReceiver: Boolean,
+    isSafeCall: Boolean
 ) {
     val position = SimpleConstraintSystemConstraintPosition //TODO
 
+    val nullableExpectedType = expectedType.withNullability(ConeNullability.NULLABLE)
+    if (isReceiver && isSafeCall) {
+        if (!csBuilder.addSubtypeConstraintIfCompatible(argumentType, nullableExpectedType, position)) {
+            sink.reportApplicability(CandidateApplicability.WRONG_RECEIVER) // TODO
+        }
+        return
+    }
+
     if (!csBuilder.addSubtypeConstraintIfCompatible(argumentType, expectedType, position)) {
-        val nullableExpectedType = expectedType.withNullability(ConeNullability.NULLABLE)
         if (!isReceiver) {
             if (!csBuilder.addSubtypeConstraintIfCompatible(argumentType, nullableExpectedType, position)) {
                 csBuilder.addSubtypeConstraint(argumentType, expectedType, position)
@@ -119,6 +132,7 @@ internal fun Candidate.resolveArgument(
     argument: FirExpression,
     parameter: FirValueParameter,
     isReceiver: Boolean,
+    isSafeCall: Boolean,
     typeProvider: (FirExpression) -> FirTypeRef?,
     sink: CheckerSink
 ) {
@@ -131,6 +145,7 @@ internal fun Candidate.resolveArgument(
         parameter.returnTypeRef,
         sink,
         isReceiver,
+        isSafeCall,
         { this.postponedAtoms += it },
         typeProvider
     )

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/CallResolver.kt

@@ -36,6 +36,7 @@ class CallInfo(
 
     val explicitReceiver: FirExpression?,
     val arguments: List<FirExpression>,
+    val isSafeCall: Boolean,
 
     val typeArguments: List<FirTypeProjection>,
     val session: FirSession,

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/PostponedArgumentsAnalyzer.kt

@@ -109,6 +109,7 @@ class PostponedArgumentsAnalyzer(
                 lambda.atom.returnTypeRef, // TODO: proper ref
                 checkerSink,
                 false,
+                false,
                 { atom = it },
                 typeProvider
             )

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/calls/ResolverParts.kt

@@ -103,10 +103,15 @@ internal sealed class CheckReceivers : ResolutionStage() {
         if (receiverParameterValue != null) {
             if (explicitReceiverExpression != null && explicitReceiverKind.shouldBeResolvedAsExplicit()) {
                 resolveArgumentExpression(
-                    candidate.csBuilder, explicitReceiverExpression,
+                    candidate.csBuilder,
+                    explicitReceiverExpression,
                     candidate.substitutor.substituteOrSelf(receiverParameterValue.type),
                     explicitReceiverExpression.typeRef,
-                    sink, isReceiver = true, typeProvider = callInfo.typeProvider, acceptLambdaAtoms = { candidate.postponedAtoms += it }
+                    sink,
+                    isReceiver = true,
+                    isSafeCall = callInfo.isSafeCall,
+                    typeProvider = callInfo.typeProvider,
+                    acceptLambdaAtoms = { candidate.postponedAtoms += it }
                 )
             }
         }
@@ -132,7 +137,14 @@ internal object CheckArguments : CheckerStage() {
         val argumentMapping =
             candidate.argumentMapping ?: throw IllegalStateException("Argument should be already mapped while checking arguments!")
         for ((argument, parameter) in argumentMapping) {
-            candidate.resolveArgument(argument, parameter, isReceiver = false, typeProvider = callInfo.typeProvider, sink = sink)
+            candidate.resolveArgument(
+                argument,
+                parameter,
+                isReceiver = false,
+                isSafeCall = false,
+                typeProvider = callInfo.typeProvider,
+                sink = sink
+            )
         }
 
         if (candidate.system.hasContradiction) {

compiler/fir/resolve/src/org/jetbrains/kotlin/fir/resolve/transformers/FirBodyResolveTransformer.kt

@@ -248,7 +248,16 @@ open class FirBodyResolveTransformer(val session: FirSession, val implicitTypeOn
 
         val receiver = qualifiedAccess.explicitReceiver?.transformSingle(this, noExpectedType)
 
-        val info = CallInfo(CallKind.VariableAccess, receiver, emptyList(), emptyList(), session, file, container!!) { it.resultType }
+        val info = CallInfo(
+            CallKind.VariableAccess,
+            receiver,
+            emptyList(),
+            qualifiedAccess.safe,
+            emptyList(),
+            session,
+            file,
+            container!!
+        ) { it.resultType }
         val resolver = CallResolver(jump, inferenceComponents)
         resolver.callInfo = info
         resolver.scopes = (scopes + localScopes).asReversed()
@@ -358,7 +367,16 @@ open class FirBodyResolveTransformer(val session: FirSession, val implicitTypeOn
         val arguments = functionCall.arguments
         val typeArguments = functionCall.typeArguments
 
-        val info = CallInfo(CallKind.Function, explicitReceiver, arguments, typeArguments, session, file, container!!) { it.resultType }
+        val info = CallInfo(
+            CallKind.Function,
+            explicitReceiver,
+            arguments,
+            functionCall.safe,
+            typeArguments,
+            session,
+            file,
+            container!!
+        ) { it.resultType }
         val resolver = CallResolver(jump, inferenceComponents)
         resolver.callInfo = info
         resolver.scopes = (scopes + localScopes).asReversed()

compiler/testData/ir/irText/expressions/bangbang.fir.txt

@@ -16,21 +16,21 @@ FILE fqName:<root> fileName:/bangbang.kt
             BRANCH
               if: CONST Boolean type=kotlin.Boolean value=true
               then: GET_VAR 'val <bangbang>: kotlin.Any? [val] declared in <root>.test1' type=kotlin.Any? origin=null
-  FUN name:test2 visibility:public modality:FINAL <> (a:kotlin.Any?) returnType:IrErrorType 
+  FUN name:test2 visibility:public modality:FINAL <> (a:kotlin.Any?) returnType:kotlin.Int
     VALUE_PARAMETER name:a index:0 type:kotlin.Any? 
     BLOCK_BODY
-      RETURN type=kotlin.Nothing from='public final fun test2 (a: kotlin.Any?): IrErrorType declared in <root>'
+      RETURN type=kotlin.Nothing from='public final fun test2 (a: kotlin.Any?): kotlin.Int declared in <root>'
-        BLOCK type=IrErrorType origin=EXCLEXCL
+        BLOCK type=kotlin.Int origin=EXCLEXCL
-          VAR name:<bangbang> type:IrErrorType [val] 
+          VAR name:<bangbang> type:kotlin.Int [val]
-            ERROR_CALL 'Unresolved reference: <Inapplicable(WRONG_RECEIVER): [kotlin/Any.hashCode]>#' type=IrErrorType
+            CALL 'public open fun hashCode (): kotlin.Int declared in kotlin.Any' type=kotlin.Int origin=null
-          WHEN type=IrErrorType origin=EXCLEXCL
+              $this: GET_VAR 'a: kotlin.Any? declared in <root>.test2' type=kotlin.Any? origin=null
+          WHEN type=kotlin.Int origin=EXCLEXCL
             BRANCH
               if: CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
-                arg0: GET_VAR 'val <bangbang>: IrErrorType [val] declared in <root>.test2' type=IrErrorType origin=null
+                arg0: GET_VAR 'val <bangbang>: kotlin.Int [val] declared in <root>.test2' type=kotlin.Int origin=null
                 arg1: CONST Null type=kotlin.Nothing? value=null
               then: THROW type=kotlin.Nothing
                 ERROR_CALL 'Unresolved reference: <Unresolved name: KotlinNullPointerException>#' type=IrErrorType
             BRANCH
               if: CONST Boolean type=kotlin.Boolean value=true
-              then: GET_VAR 'val <bangbang>: IrErrorType [val] declared in <root>.test2' type=IrErrorType origin=null
+              then: GET_VAR 'val <bangbang>: kotlin.Int [val] declared in <root>.test2' type=kotlin.Int origin=null
-

compiler/testData/ir/irText/expressions/chainOfSafeCalls.fir.txt

@@ -28,9 +28,12 @@ FILE fqName:<root> fileName:/chainOfSafeCalls.kt
       overridden:
         public open fun toString (): kotlin.String declared in kotlin.Any
       $this: VALUE_PARAMETER name:<this> type:kotlin.Any 
-  FUN name:test visibility:public modality:FINAL <> (nc:<root>.C?) returnType:IrErrorType 
+  FUN name:test visibility:public modality:FINAL <> (nc:<root>.C?) returnType:<root>.C
     VALUE_PARAMETER name:nc index:0 type:<root>.C? 
     BLOCK_BODY
-      RETURN type=kotlin.Nothing from='public final fun test (nc: <root>.C?): IrErrorType declared in <root>'
+      RETURN type=kotlin.Nothing from='public final fun test (nc: <root>.C?): <root>.C declared in <root>'
-        ERROR_CALL 'Unresolved reference: <Unresolved name: foo>#' type=IrErrorType
+        CALL 'public final fun foo (): <root>.C declared in <root>.C' type=<root>.C origin=null
-
+          $this: CALL 'public final fun foo (): <root>.C declared in <root>.C' type=<root>.C origin=null
+            $this: CALL 'public final fun bar (): <root>.C? declared in <root>.C' type=<root>.C? origin=null
+              $this: CALL 'public final fun foo (): <root>.C declared in <root>.C' type=<root>.C origin=null
+                $this: GET_VAR 'nc: <root>.C? declared in <root>.test' type=<root>.C? origin=null

compiler/testData/ir/irText/expressions/kt30020.fir.txt

@@ -55,20 +55,21 @@ FILE fqName:<root> fileName:/kt30020.kt
               if: CONST Boolean type=kotlin.Boolean value=true
               then: GET_VAR 'val <bangbang>: kotlin.collections.MutableList<kotlin.Any> [val] declared in <root>.test' type=kotlin.collections.MutableList<kotlin.Any> origin=null
       ERROR_CALL 'Unresolved reference: R|<local>/<complex-set>|' type=IrErrorType
-      VAR name:<complex-set> type:IrErrorType [val] 
+      VAR name:<complex-set> type:kotlin.collections.MutableList<kotlin.Any> [val]
-        BLOCK type=IrErrorType origin=EXCLEXCL
+        BLOCK type=kotlin.collections.MutableList<kotlin.Any> origin=EXCLEXCL
-          VAR name:<bangbang> type:IrErrorType [val] 
+          VAR name:<bangbang> type:kotlin.collections.MutableList<kotlin.Any> [val]
-            ERROR_CALL 'Unresolved reference: <Inapplicable(WRONG_RECEIVER): [/X.f]>#' type=IrErrorType
+            CALL 'public abstract fun f (): kotlin.collections.MutableList<kotlin.Any> declared in <root>.X' type=kotlin.collections.MutableList<kotlin.Any> origin=null
-          WHEN type=IrErrorType origin=EXCLEXCL
+              $this: GET_VAR 'nx: <root>.X? declared in <root>.test' type=<root>.X? origin=null
+          WHEN type=kotlin.collections.MutableList<kotlin.Any> origin=EXCLEXCL
             BRANCH
               if: CALL 'public final fun EQEQ (arg0: kotlin.Any?, arg1: kotlin.Any?): kotlin.Boolean declared in kotlin.internal.ir' type=kotlin.Boolean origin=EQEQ
-                arg0: GET_VAR 'val <bangbang>: IrErrorType [val] declared in <root>.test' type=IrErrorType origin=null
+                arg0: GET_VAR 'val <bangbang>: kotlin.collections.MutableList<kotlin.Any> [val] declared in <root>.test' type=kotlin.collections.MutableList<kotlin.Any> origin=null
                 arg1: CONST Null type=kotlin.Nothing? value=null
               then: THROW type=kotlin.Nothing
                 CONSTRUCTOR_CALL 'public constructor <init> () declared in kotlin.KotlinNullPointerException' type=kotlin.KotlinNullPointerException origin=null
             BRANCH
               if: CONST Boolean type=kotlin.Boolean value=true
-              then: GET_VAR 'val <bangbang>: IrErrorType [val] declared in <root>.test' type=IrErrorType origin=null
+              then: GET_VAR 'val <bangbang>: kotlin.collections.MutableList<kotlin.Any> [val] declared in <root>.test' type=kotlin.collections.MutableList<kotlin.Any> origin=null
       ERROR_CALL 'Unresolved reference: R|<local>/<complex-set>|' type=IrErrorType
   FUN name:testExtensionReceiver visibility:public modality:FINAL <> () returnType:kotlin.Unit 
     BLOCK_BODY

compiler/testData/ir/irText/expressions/safeCallWithIncrementDecrement.fir.txt

@@ -31,7 +31,8 @@ FILE fqName:test fileName:/safeCallWithIncrementDecrement.kt
   FUN name:inc visibility:public modality:FINAL <> () returnType:kotlin.Int? 
     BLOCK_BODY
       RETURN type=kotlin.Nothing from='public final fun inc (): kotlin.Int? declared in test'
-        CALL 'public final fun inc (): kotlin.Int? declared in test' type=kotlin.Int? origin=null
+        CALL 'public final fun inc (): kotlin.Int declared in kotlin.Int' type=kotlin.Int origin=null
+          $this: ERROR_CALL 'Unresolved reference: this#' type=kotlin.Int?
   FUN name:get visibility:public modality:FINAL <> (index:kotlin.Int) returnType:kotlin.Int 
     VALUE_PARAMETER name:index index:0 type:kotlin.Int 
     BLOCK_BODY

compiler/testData/ir/irText/expressions/safeCalls.fir.txt

@@ -67,24 +67,25 @@ FILE fqName:<root> fileName:/safeCalls.kt
     VALUE_PARAMETER name:x index:0 type:kotlin.String? 
     BLOCK_BODY
       RETURN type=kotlin.Nothing from='public final fun test2 (x: kotlin.String?): IrErrorType declared in <root>'
-        ERROR_CALL 'Unresolved reference: <Inapplicable(WRONG_RECEIVER): [kotlin/Any.hashCode, kotlin/Any.hashCode]>#' type=IrErrorType
+        ERROR_CALL 'Unresolved reference: <Ambiguity: hashCode, [kotlin/Any.hashCode, kotlin/Any.hashCode]>#' type=IrErrorType
   FUN name:test3 visibility:public modality:FINAL <> (x:kotlin.String?, y:kotlin.Any?) returnType:IrErrorType 
     VALUE_PARAMETER name:x index:0 type:kotlin.String? 
     VALUE_PARAMETER name:y index:1 type:kotlin.Any? 
     BLOCK_BODY
       RETURN type=kotlin.Nothing from='public final fun test3 (x: kotlin.String?, y: kotlin.Any?): IrErrorType declared in <root>'
-        ERROR_CALL 'Unresolved reference: <Inapplicable(WRONG_RECEIVER): [kotlin/Any.equals, kotlin/Any.equals]>#' type=IrErrorType
+        ERROR_CALL 'Unresolved reference: <Ambiguity: equals, [kotlin/Any.equals, kotlin/Any.equals]>#' type=IrErrorType
           GET_VAR 'y: kotlin.Any? declared in <root>.test3' type=kotlin.Any? origin=null
   FUN name:test4 visibility:public modality:FINAL <> (x:<root>.Ref?) returnType:kotlin.Unit 
     VALUE_PARAMETER name:x index:0 type:<root>.Ref? 
     BLOCK_BODY
       SET_FIELD 'FIELD PROPERTY_BACKING_FIELD name:value type:kotlin.Int visibility:public ' type=kotlin.Int origin=null
         value: CONST Int type=kotlin.Int value=0
-  FUN name:test5 visibility:public modality:FINAL <> (s:kotlin.String?) returnType:IrErrorType 
+  FUN name:test5 visibility:public modality:FINAL <> (s:kotlin.String?) returnType:kotlin.Int
     VALUE_PARAMETER name:s index:0 type:kotlin.String? 
     BLOCK_BODY
-      RETURN type=kotlin.Nothing from='public final fun test5 (s: kotlin.String?): IrErrorType declared in <root>'
+      RETURN type=kotlin.Nothing from='public final fun test5 (s: kotlin.String?): kotlin.Int declared in <root>'
-        ERROR_CALL 'Unresolved reference: <Inapplicable(WRONG_RECEIVER): [/IHost.extLength]>#' type=IrErrorType
+        CALL 'public open fun extLength (): kotlin.Int declared in <root>.IHost' type=kotlin.Int origin=null
+          $this: GET_VAR 's: kotlin.String? declared in <root>.test5' type=kotlin.String? origin=null
   FUN name:foo visibility:public modality:FINAL <> () returnType:kotlin.Int 
     BLOCK_BODY
       RETURN type=kotlin.Nothing from='public final fun foo (): kotlin.Int declared in <root>'

compiler/testData/ir/irText/expressions/temporaryInEnumEntryInitializer.fir.txt

@@ -31,7 +31,8 @@ FILE fqName:<root> fileName:/temporaryInEnumEntryInitializer.kt
       CONSTRUCTOR visibility:public <> () returnType:<root>.En.ENTRY [primary] 
         BLOCK_BODY
           DELEGATING_CONSTRUCTOR_CALL 'private constructor <init> (x: kotlin.String?) [primary] declared in <root>.En'
-            x: CALL 'public final fun toString (): kotlin.String declared in kotlin' type=kotlin.String origin=null
+            x: CALL 'public open fun toString (): kotlin.String declared in kotlin.Any' type=kotlin.String origin=null
+              $this: CALL 'public final fun <get-n> (): kotlin.Any? declared in <root>' type=kotlin.Any? origin=null
           INSTANCE_INITIALIZER_CALL classDescriptor='CLASS ENUM_ENTRY name:ENTRY modality:FINAL visibility:public superTypes:[<root>.En]'
       FUN FAKE_OVERRIDE name:clone visibility:protected modality:FINAL <> ($this:kotlin.Enum) returnType:kotlin.Any 
         overridden:

compiler/testData/ir/irText/expressions/temporaryInInitBlock.fir.txt

@@ -18,7 +18,8 @@ FILE fqName:<root> fileName:/temporaryInInitBlock.kt
     ANONYMOUS_INITIALIZER isStatic=false
       BLOCK_BODY
         SET_FIELD 'FIELD PROPERTY_BACKING_FIELD name:s type:kotlin.String? visibility:public [final] ' type=kotlin.String? origin=null
-          value: CALL 'public final fun toString (): kotlin.String declared in kotlin' type=kotlin.String origin=null
+          value: CALL 'public open fun toString (): kotlin.String declared in kotlin.Any' type=kotlin.String origin=null
+            $this: GET_VAR 'x: kotlin.Any? declared in <root>.C.<init>' type=kotlin.Any? origin=null
     FUN FAKE_OVERRIDE name:equals visibility:public modality:OPEN <> ($this:kotlin.Any, other:kotlin.Any?) returnType:kotlin.Boolean 
       overridden:
         public open fun equals (other: kotlin.Any?): kotlin.Boolean declared in kotlin.Any