[K2] Disappeared UNSUPPORTED_FEATURE (1)

Added a check for the enabled context receivers feature flag for typeRef.

^KT-59913

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/CommonTypeCheckers.kt

@@ -21,5 +21,6 @@ object CommonTypeCheckers : TypeCheckers() {
         FirDuplicateParameterNameInFunctionTypeChecker,
         FirOptionalExpectationTypeChecker,
         FirIncompatibleClassTypeChecker,
+        FirContextReceiversTypeChecker,
     )
 }

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/type/FirContextReceiversTypeChecker.kt

@@ -0,0 +1,33 @@
+/*
+ * Copyright 2010-2021 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.fir.analysis.checkers.type
+
+import org.jetbrains.kotlin.KtFakeSourceElementKind
+import org.jetbrains.kotlin.config.LanguageFeature
+import org.jetbrains.kotlin.diagnostics.DiagnosticReporter
+import org.jetbrains.kotlin.diagnostics.reportOn
+import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
+import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors
+import org.jetbrains.kotlin.fir.types.*
+
+object FirContextReceiversTypeChecker : FirTypeRefChecker() {
+    override fun check(typeRef: FirTypeRef, context: CheckerContext, reporter: DiagnosticReporter) {
+        if (context.languageVersionSettings.supportsFeature(LanguageFeature.ContextReceivers)) return
+        if (typeRef !is FirResolvedTypeRef) return
+        val source = typeRef.source ?: return
+        if (source.kind is KtFakeSourceElementKind) return
+
+        if (typeRef.coneType.hasContextReceivers) {
+            reporter.reportOn(
+                source,
+                FirErrors.UNSUPPORTED_FEATURE,
+                LanguageFeature.ContextReceivers to context.languageVersionSettings,
+                context
+            )
+        }
+    }
+}
+

compiler/testData/diagnostics/tests/extensions/contextReceivers/unsupported.fir.kt

@@ -1,8 +1,8 @@
 // !DIAGNOSTICS: -UNCHECKED_CAST
 
 context(Any)
-fun f(g: context(Any) () -> Unit, value: Any): context(A) () -> Unit {
-    return value as (context(A) () -> Unit)
+fun f(g: <!UNSUPPORTED_FEATURE!>context(Any) () -> Unit<!>, value: Any): <!UNSUPPORTED_FEATURE!>context(A) () -> Unit<!> {
+    return value as <!UNSUPPORTED_FEATURE!>(context(A) () -> Unit)<!>
 }
 
 fun f(g: () -> Unit, value: Any) : () -> Unit {