NI: Allow to resolve to functions with SAM conversion and passing array without spread as vararg (with warning)

^KT-35224 Fixed

compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/components/KotlinCallCompleter.kt

@@ -6,6 +6,8 @@
 package org.jetbrains.kotlin.resolve.calls.components
 
 import org.jetbrains.kotlin.config.LanguageFeature
+import org.jetbrains.kotlin.descriptors.FunctionDescriptor
+import org.jetbrains.kotlin.descriptors.synthetic.SyntheticMemberDescriptor
 import org.jetbrains.kotlin.resolve.calls.inference.NewConstraintSystem
 import org.jetbrains.kotlin.resolve.calls.inference.addSubtypeConstraintIfCompatible
 import org.jetbrains.kotlin.resolve.calls.inference.components.KotlinConstraintSystemCompleter
@@ -45,6 +47,7 @@ class KotlinCallCompleter(
 
         candidate.addExpectedTypeConstraint(returnType, expectedType)
         candidate.addExpectedTypeFromCastConstraint(returnType, resolutionCallbacks)
+        candidate.checkSamWithVararg(diagnosticHolder)
 
         return if (resolutionCallbacks.inferenceSession.shouldRunCompletion(candidate))
             candidate.runCompletion(
@@ -56,6 +59,22 @@ class KotlinCallCompleter(
             candidate.asCallResolutionResult(ConstraintSystemCompletionMode.PARTIAL, diagnosticHolder)
     }
 
+    private fun KotlinResolutionCandidate.checkSamWithVararg(diagnosticHolder: KotlinDiagnosticsHolder.SimpleHolder) {
+        val samConversionPerArgumentWithWarningsForVarargAfterSam =
+            callComponents.languageVersionSettings.supportsFeature(LanguageFeature.SamConversionPerArgument) &&
+                    !callComponents.languageVersionSettings.supportsFeature(LanguageFeature.ProhibitVarargAsArrayAfterSamArgument)
+
+        if (samConversionPerArgumentWithWarningsForVarargAfterSam && resolvedCall.candidateDescriptor is SyntheticMemberDescriptor<*>) {
+            val declarationDescriptor = resolvedCall.candidateDescriptor.baseDescriptorForSynthetic as? FunctionDescriptor ?: return
+
+            if (declarationDescriptor.valueParameters.lastOrNull()?.isVararg == true) {
+                diagnosticHolder.addDiagnostic(
+                    ResolvedToSamWithVarargDiagnostic(resolvedCall.atom.argumentsInParenthesis.lastOrNull() ?: return)
+                )
+            }
+        }
+    }
+
     fun createAllCandidatesResult(
         candidates: Collection<KotlinResolutionCandidate>,
         expectedType: UnwrappedType?,

compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/components/ResolutionParts.kt

@@ -294,7 +294,11 @@ private fun KotlinResolutionCandidate.getExpectedTypeWithSAMConversion(
     argument: KotlinCallArgument,
     candidateParameter: ParameterDescriptor
 ): UnwrappedType? {
-    if (!callComponents.languageVersionSettings.supportsFeature(LanguageFeature.SamConversionPerArgument)) return null
+    val generatingAdditionalSamCandidateIsEnabled =
+        !callComponents.languageVersionSettings.supportsFeature(LanguageFeature.SamConversionPerArgument) &&
+                !callComponents.languageVersionSettings.supportsFeature(LanguageFeature.ProhibitVarargAsArrayAfterSamArgument)
+
+    if (generatingAdditionalSamCandidateIsEnabled) return null
     if (!callComponents.samConversionTransformer.shouldRunSamConversionForFunction(resolvedCall.candidateDescriptor)) return null
 
     val argumentIsFunctional = when (argument) {

compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/model/KotlinCallDiagnostics.kt

@@ -202,4 +202,10 @@ class OnlyInputTypesDiagnostic(val typeVariable: NewTypeVariable) : KotlinCallDi
     override fun report(reporter: DiagnosticReporter) {
         reporter.onCall(this)
     }
-}
+}
+
+class ResolvedToSamWithVarargDiagnostic(val argument: KotlinCallArgument) : KotlinCallDiagnostic(RESOLVED_TO_SAM_WITH_VARARG) {
+    override fun report(reporter: DiagnosticReporter) {
+        reporter.onCallArgument(argument, this)
+    }
+}

compiler/resolution/src/org/jetbrains/kotlin/resolve/calls/tower/ImplicitScopeTower.kt

@@ -83,6 +83,7 @@ enum class ResolutionCandidateApplicability {
     INAPPLICABLE_ARGUMENTS_MAPPING_ERROR, // arguments not mapped to parameters (i.e. different size of arguments and parameters)
     INAPPLICABLE_WRONG_RECEIVER, // receiver not matched
     HIDDEN, // removed from resolve
+    RESOLVED_TO_SAM_WITH_VARARG, // migration warning up to 1.5 (when resolve to function with SAM conversion and array without spread as vararg)
 }
 
 abstract class ResolutionDiagnostic(candidateApplicability: ResolutionCandidateApplicability) :