IR: introduce abstract class IrDeclarationBase

The main purpose of this class is to improve performance of IR visitors
and transformers. `IrElementVisitor.visitDeclaration` now takes
IrDeclarationBase as a parameter, and therefore the call to `accept`
there is now a virtual class call, instead of an interface call.

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/CheckIrElementVisitor.kt

@@ -312,7 +312,7 @@ class CheckIrElementVisitor(
         expression.symbol.ensureBound(expression)
     }
 
-    override fun visitDeclaration(declaration: IrDeclaration) {
+    override fun visitDeclaration(declaration: IrDeclarationBase) {
         super.visitDeclaration(declaration)
 
         if (declaration is IrOverridableDeclaration<*>) {

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/IrValidator.kt

@@ -98,7 +98,7 @@ object CheckDeclarationParentsVisitor : IrElementVisitor<Unit, IrDeclarationPare
         element.acceptChildren(this, element as? IrDeclarationParent ?: data)
     }
 
-    override fun visitDeclaration(declaration: IrDeclaration, data: IrDeclarationParent?) {
+    override fun visitDeclaration(declaration: IrDeclarationBase, data: IrDeclarationParent?) {
         checkParent(declaration, data)
         super.visitDeclaration(declaration, data)
     }

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/Lower.kt

@@ -127,7 +127,7 @@ fun BodyLoweringPass.runOnFilePostfix(irFile: IrFile, withLocalDeclarations: Boo
                 element.acceptChildren(this, data)
             }
 
-            override fun visitDeclaration(declaration: IrDeclaration, data: IrDeclaration?) {
+            override fun visitDeclaration(declaration: IrDeclarationBase, data: IrDeclaration?) {
                 declaration.acceptChildren(this, declaration)
             }
 

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/ir/IrInlineUtils.kt

@@ -78,7 +78,7 @@ private fun IrBody.move(
         return super.visitBlock(expression)
     }
 
-    override fun visitDeclaration(declaration: IrDeclaration): IrStatement {
+    override fun visitDeclaration(declaration: IrDeclarationBase): IrStatement {
         if (declaration.parent == source)
             declaration.parent = target
         return super.visitDeclaration(declaration)

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/ir/IrUtils.kt

@@ -364,7 +364,7 @@ object SetDeclarationsParentVisitor : IrElementVisitor<Unit, IrDeclarationParent
         }
     }
 
-    override fun visitDeclaration(declaration: IrDeclaration, data: IrDeclarationParent) {
+    override fun visitDeclaration(declaration: IrDeclarationBase, data: IrDeclarationParent) {
         declaration.parent = data
         super.visitDeclaration(declaration, data)
     }

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/InlineClassDeclarationLowering.kt

@@ -105,7 +105,7 @@ class InlineClassLowering(val context: CommonBackendContext) {
                                 return expression
                             }
 
-                            override fun visitDeclaration(declaration: IrDeclaration): IrStatement {
+                            override fun visitDeclaration(declaration: IrDeclarationBase): IrStatement {
                                 declaration.transformChildrenVoid(this)
                                 if (declaration.parent == irConstructor)
                                     declaration.parent = staticMethod
@@ -142,7 +142,7 @@ class InlineClassLowering(val context: CommonBackendContext) {
                 statements.addAll((functionBody as IrBlockBody).statements)
 
                 transformChildrenVoid(object : IrElementTransformerVoid() {
-                    override fun visitDeclaration(declaration: IrDeclaration): IrStatement {
+                    override fun visitDeclaration(declaration: IrDeclarationBase): IrStatement {
                         declaration.transformChildrenVoid(this)
                         if (declaration.parent == function)
                             declaration.parent = staticMethod

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/LocalDeclarationsLowering.kt

@@ -442,7 +442,7 @@ class LocalDeclarationsLowering(
                 return super.visitDeclarationReference(expression)
             }
 
-            override fun visitDeclaration(declaration: IrDeclaration): IrStatement {
+            override fun visitDeclaration(declaration: IrDeclarationBase): IrStatement {
                 if (declaration is IrSymbolOwner && declaration in transformedDeclarations) {
                     TODO()
                 }

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/SharedVariablesLowering.kt

@@ -91,7 +91,7 @@ class SharedVariablesLowering(val context: BackendContext) : BodyLoweringPass {
                     }
                 }
 
-                override fun visitDeclaration(declaration: IrDeclaration, data: IrDeclarationParent?) {
+                override fun visitDeclaration(declaration: IrDeclarationBase, data: IrDeclarationParent?) {
                     super.visitDeclaration(declaration, declaration as? IrDeclarationParent ?: data)
                 }
 

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/StringConcatenationLowering.kt

@@ -24,10 +24,7 @@ import org.jetbrains.kotlin.ir.builders.IrBuilderWithScope
 import org.jetbrains.kotlin.ir.builders.createTmpVariable
 import org.jetbrains.kotlin.ir.builders.irCall
 import org.jetbrains.kotlin.ir.builders.irGet
-import org.jetbrains.kotlin.ir.declarations.IrDeclaration
-import org.jetbrains.kotlin.ir.declarations.IrFile
-import org.jetbrains.kotlin.ir.declarations.IrSimpleFunction
-import org.jetbrains.kotlin.ir.declarations.IrSymbolDeclaration
+import org.jetbrains.kotlin.ir.declarations.*
 import org.jetbrains.kotlin.ir.expressions.IrExpression
 import org.jetbrains.kotlin.ir.expressions.IrStringConcatenation
 import org.jetbrains.kotlin.ir.types.IrType
@@ -106,7 +103,7 @@ private class StringConcatenationTransformer(val lower: StringConcatenationLower
         }
     }
 
-    override fun visitDeclaration(declaration: IrDeclaration): IrStatement {
+    override fun visitDeclaration(declaration: IrDeclarationBase): IrStatement {
         if (declaration !is IrSymbolDeclaration<*>) {
             return super.visitDeclaration(declaration)
         }
@@ -120,4 +117,4 @@ private class StringConcatenationTransformer(val lower: StringConcatenationLower
             return this@with
         }
     }
-}
+}

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/phaser/DumperVerifier.kt

@@ -70,7 +70,7 @@ fun dumpIrElement(actionState: ActionState, data: IrElement, context: Any?): Str
                 element.acceptChildrenVoid(this)
             }
 
-            override fun visitDeclaration(declaration: IrDeclaration) {
+            override fun visitDeclaration(declaration: IrDeclarationBase) {
                 if (declaration is IrDeclarationWithName && FqName(dumpOnlyFqName) == declaration.fqNameWhenAvailable) {
                     dumpText += declaration.dump()
                 } else {