[FIR] Report UNSUPPORTED for default value in function type

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

@@ -163,4 +163,9 @@ object CommonDeclarationCheckers : DeclarationCheckers() {
         get() = setOf(
             FirEnumCompanionInEnumConstructorCallChecker,
         )
+
+    override val valueParameterCheckers: Set<FirValueParameterChecker>
+        get() = setOf(
+            FirUnsupportedDefaultValueInFunctionTypeChecker
+        )
 }

compiler/fir/checkers/src/org/jetbrains/kotlin/fir/analysis/checkers/declaration/FirUnsupportedDefaultValueInFunctionTypeChecker.kt

@@ -0,0 +1,23 @@
+/*
+ * Copyright 2010-2022 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.declaration
+
+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.declarations.FirValueParameter
+import org.jetbrains.kotlin.fir.resolve.diagnostics.ConeUnsupportedDefaultValueInFunctionType
+import org.jetbrains.kotlin.fir.types.FirErrorTypeRef
+
+object FirUnsupportedDefaultValueInFunctionTypeChecker : FirValueParameterChecker() {
+    override fun check(declaration: FirValueParameter, context: CheckerContext, reporter: DiagnosticReporter) {
+        val diagnostic = ((declaration.defaultValue?.typeRef as? FirErrorTypeRef)?.diagnostic as? ConeUnsupportedDefaultValueInFunctionType)
+        if (diagnostic != null) {
+            reporter.reportOn(diagnostic.source, FirErrors.UNSUPPORTED, diagnostic.reason, context)
+        }
+    }
+}

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

@@ -11,10 +11,14 @@ import org.jetbrains.kotlin.fakeElement
 import org.jetbrains.kotlin.fir.*
 import org.jetbrains.kotlin.fir.declarations.FirFile
 import org.jetbrains.kotlin.fir.declarations.FirResolvePhase
+import org.jetbrains.kotlin.fir.declarations.FirValueParameter
 import org.jetbrains.kotlin.fir.diagnostics.ConeDiagnostic
 import org.jetbrains.kotlin.fir.diagnostics.ConeSimpleDiagnostic
 import org.jetbrains.kotlin.fir.diagnostics.ConeUnexpectedTypeArgumentsError
+import org.jetbrains.kotlin.fir.expressions.FirStatement
 import org.jetbrains.kotlin.fir.resolve.SupertypeSupplier
+import org.jetbrains.kotlin.fir.resolve.diagnostics.ConeUnsupportedDefaultValueInFunctionType
+import org.jetbrains.kotlin.fir.resolve.transformers.body.resolve.resultType
 import org.jetbrains.kotlin.fir.resolve.typeResolver
 import org.jetbrains.kotlin.fir.types.*
 import org.jetbrains.kotlin.fir.types.builder.buildErrorTypeRef
@@ -180,4 +184,14 @@ class FirSpecificTypeResolverTransformer(
     override fun transformImplicitTypeRef(implicitTypeRef: FirImplicitTypeRef, data: ScopeClassDeclaration): FirTypeRef {
         return implicitTypeRef
     }
+
+    override fun transformValueParameter(valueParameter: FirValueParameter, data: ScopeClassDeclaration): FirStatement {
+        val result = transformElement(valueParameter, data)
+        result.defaultValue?.let {
+            it.resultType = buildErrorTypeRef {
+                diagnostic = ConeUnsupportedDefaultValueInFunctionType(it.source)
+            }
+        }
+        return result
+    }
 }

compiler/fir/semantics/src/org/jetbrains/kotlin/fir/resolve/diagnostics/ConeDiagnostics.kt

@@ -204,6 +204,9 @@ class ConeImportFromSingleton(val name: Name) : ConeDiagnostic {
 
 open class ConeUnsupported(override val reason: String, val source: KtSourceElement? = null) : ConeDiagnostic
 
+open class ConeUnsupportedDefaultValueInFunctionType(source: KtSourceElement? = null) :
+    ConeUnsupported("Default value of parameter in function type", source)
+
 class ConeUnresolvedParentInImport(val parentClassId: ClassId) : ConeDiagnostic {
     override val reason: String
         get() = "unresolved import"

compiler/testData/diagnostics/tests/DefaultValueForParameterInFunctionType.fir.kt

@@ -1,20 +0,0 @@
-// !DIAGNOSTICS: -UNUSED_PARAMETER -UNUSED_VARIABLE
-
-fun f(x: Int = 0) {}
-
-val inVal: (x: Int = 0)->Unit = {}
-
-fun inParam(fn: (x: Int = 0)->Unit) {}
-
-fun inParamNested(fn1: (fn2: (n: Int = 0)->Unit)->Unit) {}
-
-fun inReturn(): (x: Int = 0)->Unit = {}
-
-class A : (Int)->Unit {
-    override fun invoke(p1: Int) {
-        var lambda: (x: Int = 0)->Unit = {}
-    }
-
-    val prop: (x: Int = 0)->Unit
-        get(): (x: Int = 0)->Unit = {}
-}

compiler/testData/diagnostics/tests/DefaultValueForParameterInFunctionType.kt

@@ -1,3 +1,4 @@
+// FIR_IDENTICAL
 // !DIAGNOSTICS: -UNUSED_PARAMETER -UNUSED_VARIABLE
 
 fun f(x: Int = 0) {}