[FIR] Unity FirCallableDeclaration and FirCallableMemberDeclaration

After removal of all diamonds in FirDeclaration hierarchy
  FirCallableMemberDeclaration was only one inheritor of
  FirCallableDeclaration, so there is no need to keep them both

compiler/fir/java/src/org/jetbrains/kotlin/fir/java/enhancement/SignatureEnhancement.kt

@@ -40,7 +40,7 @@ import org.jetbrains.kotlin.utils.addToStdlib.safeAs
 class FirSignatureEnhancement(
     private val owner: FirRegularClass,
     private val session: FirSession,
-    private val overridden: FirSimpleFunction.() -> List<FirCallableMemberDeclaration>
+    private val overridden: FirSimpleFunction.() -> List<FirCallableDeclaration>
 ) {
     /*
      * FirSignatureEnhancement may be created with library session which doesn't have single module data,
@@ -306,7 +306,7 @@ class FirSignatureEnhancement(
 
     private fun enhanceReceiverType(
         ownerFunction: FirJavaMethod,
-        overriddenMembers: List<FirCallableMemberDeclaration>,
+        overriddenMembers: List<FirCallableDeclaration>,
         memberContext: FirJavaEnhancementContext
     ): FirResolvedTypeRef {
         val signatureParts = ownerFunction.partsForValueParameter(
@@ -322,7 +322,7 @@ class FirSignatureEnhancement(
 
     private fun enhanceValueParameterType(
         ownerFunction: FirFunction,
-        overriddenMembers: List<FirCallableMemberDeclaration>,
+        overriddenMembers: List<FirCallableDeclaration>,
         hasReceiver: Boolean,
         memberContext: FirJavaEnhancementContext,
         predefinedEnhancementInfo: PredefinedFunctionEnhancementInfo?,
@@ -348,8 +348,8 @@ class FirSignatureEnhancement(
     }
 
     private fun enhanceReturnType(
-        owner: FirCallableMemberDeclaration,
-        overriddenMembers: List<FirCallableMemberDeclaration>,
+        owner: FirCallableDeclaration,
+        overriddenMembers: List<FirCallableDeclaration>,
         memberContext: FirJavaEnhancementContext,
         predefinedEnhancementInfo: PredefinedFunctionEnhancementInfo?
     ): FirResolvedTypeRef {
@@ -370,21 +370,21 @@ class FirSignatureEnhancement(
     }
 
     private sealed class TypeInSignature {
-        abstract fun getTypeRef(member: FirCallableMemberDeclaration): FirTypeRef
+        abstract fun getTypeRef(member: FirCallableDeclaration): FirTypeRef
 
         object Return : TypeInSignature() {
-            override fun getTypeRef(member: FirCallableMemberDeclaration): FirTypeRef = member.returnTypeRef
+            override fun getTypeRef(member: FirCallableDeclaration): FirTypeRef = member.returnTypeRef
         }
 
         object Receiver : TypeInSignature() {
-            override fun getTypeRef(member: FirCallableMemberDeclaration): FirTypeRef {
+            override fun getTypeRef(member: FirCallableDeclaration): FirTypeRef {
                 if (member is FirJavaMethod) return member.valueParameters[0].returnTypeRef
                 return member.receiverTypeRef!!
             }
         }
 
         class ValueParameter(val hasReceiver: Boolean, val index: Int) : TypeInSignature() {
-            override fun getTypeRef(member: FirCallableMemberDeclaration): FirTypeRef {
+            override fun getTypeRef(member: FirCallableDeclaration): FirTypeRef {
                 if (hasReceiver && member is FirJavaMethod) {
                     return member.valueParameters[index + 1].returnTypeRef
                 }
@@ -395,12 +395,12 @@ class FirSignatureEnhancement(
 
     private fun FirFunction.partsForValueParameter(
         typeQualifierResolver: FirAnnotationTypeQualifierResolver,
-        overriddenMembers: List<FirCallableMemberDeclaration>,
+        overriddenMembers: List<FirCallableDeclaration>,
         // TODO: investigate if it's really can be a null (check properties' with extension overrides in Java)
         parameterContainer: FirAnnotationContainer?,
         methodContext: FirJavaEnhancementContext,
         typeInSignature: TypeInSignature
-    ): EnhancementSignatureParts = (this as FirCallableMemberDeclaration).parts(
+    ): EnhancementSignatureParts = (this as FirCallableDeclaration).parts(
         typeQualifierResolver,
         overriddenMembers,
         parameterContainer, false,
@@ -411,9 +411,9 @@ class FirSignatureEnhancement(
         typeInSignature
     )
 
-    private fun FirCallableMemberDeclaration.parts(
+    private fun FirCallableDeclaration.parts(
         typeQualifierResolver: FirAnnotationTypeQualifierResolver,
-        overriddenMembers: List<FirCallableMemberDeclaration>,
+        overriddenMembers: List<FirCallableDeclaration>,
         typeContainer: FirAnnotationContainer?,
         isCovariant: Boolean,
         containerContext: FirJavaEnhancementContext,

compiler/fir/java/src/org/jetbrains/kotlin/fir/java/scopes/JavaClassMembersEnhancementScope.kt

@@ -6,7 +6,7 @@
 package org.jetbrains.kotlin.fir.java.scopes
 
 import org.jetbrains.kotlin.fir.FirSession
-import org.jetbrains.kotlin.fir.declarations.FirCallableMemberDeclaration
+import org.jetbrains.kotlin.fir.declarations.FirCallableDeclaration
 import org.jetbrains.kotlin.fir.declarations.FirProperty
 import org.jetbrains.kotlin.fir.declarations.FirSimpleFunction
 import org.jetbrains.kotlin.fir.java.enhancement.FirSignatureEnhancement
@@ -64,14 +64,14 @@ class JavaClassMembersEnhancementScope(
         return super.processFunctionsByName(name, processor)
     }
 
-    private fun FirCallableMemberDeclaration.overriddenMembers(name: Name): List<FirCallableMemberDeclaration> {
+    private fun FirCallableDeclaration.overriddenMembers(name: Name): List<FirCallableDeclaration> {
         val backMap = overrideBindCache.getOrPut(name) {
             useSiteMemberScope
                 .overrideByBase
                 .toList()
                 .groupBy({ (_, key) -> key }, { (value) -> value })
         }
-        return backMap[this.symbol]?.map { it.fir as FirCallableMemberDeclaration } ?: emptyList()
+        return backMap[this.symbol]?.map { it.fir } ?: emptyList()
     }
 
     override fun processClassifiersByNameWithSubstitution(name: Name, processor: (FirClassifierSymbol<*>, ConeSubstitutor) -> Unit) {

compiler/fir/java/src/org/jetbrains/kotlin/fir/java/scopes/JavaOverrideChecker.kt

@@ -7,7 +7,7 @@ package org.jetbrains.kotlin.fir.java.scopes
 
 import org.jetbrains.kotlin.descriptors.Modality
 import org.jetbrains.kotlin.fir.FirSession
-import org.jetbrains.kotlin.fir.declarations.FirCallableMemberDeclaration
+import org.jetbrains.kotlin.fir.declarations.FirCallableDeclaration
 import org.jetbrains.kotlin.fir.declarations.FirProperty
 import org.jetbrains.kotlin.fir.declarations.FirSimpleFunction
 import org.jetbrains.kotlin.fir.declarations.FirTypeParameterRef
@@ -101,7 +101,7 @@ class JavaOverrideChecker internal constructor(
             argument is ConeKotlinTypeProjection && argument.type.isTypeParameterDependent()
         }
 
-    private fun FirCallableMemberDeclaration.isTypeParameterDependent(): Boolean =
+    private fun FirCallableDeclaration.isTypeParameterDependent(): Boolean =
         typeParameters.isNotEmpty() || returnTypeRef.isTypeParameterDependent() ||
                 receiverTypeRef.isTypeParameterDependent() ||
                 this is FirSimpleFunction && valueParameters.any { it.returnTypeRef.isTypeParameterDependent() }
@@ -127,7 +127,7 @@ class JavaOverrideChecker internal constructor(
         }
     }
 
-    private fun FirCallableMemberDeclaration.extractTypeParametersTo(result: MutableCollection<FirTypeParameterRef>) {
+    private fun FirCallableDeclaration.extractTypeParametersTo(result: MutableCollection<FirTypeParameterRef>) {
         result += typeParameters
         returnTypeRef.extractTypeParametersTo(result)
         receiverTypeRef?.extractTypeParametersTo(result)
@@ -137,8 +137,8 @@ class JavaOverrideChecker internal constructor(
     }
 
     override fun buildTypeParametersSubstitutorIfCompatible(
-        overrideCandidate: FirCallableMemberDeclaration,
-        baseDeclaration: FirCallableMemberDeclaration
+        overrideCandidate: FirCallableDeclaration,
+        baseDeclaration: FirCallableDeclaration
     ): ConeSubstitutor {
         if (!overrideCandidate.isTypeParameterDependent() && !baseDeclaration.isTypeParameterDependent()) {
             return ConeSubstitutor.Empty
@@ -162,7 +162,7 @@ class JavaOverrideChecker internal constructor(
         }
     }
 
-    override fun isOverriddenProperty(overrideCandidate: FirCallableMemberDeclaration, baseDeclaration: FirProperty): Boolean {
+    override fun isOverriddenProperty(overrideCandidate: FirCallableDeclaration, baseDeclaration: FirProperty): Boolean {
         if (baseDeclaration.modality == Modality.FINAL) return false
         val receiverTypeRef = baseDeclaration.receiverTypeRef
         return when (overrideCandidate) {