Fir2Ir: add FirIrProvider

compiler/fir/fir2ir/src/org/jetbrains/kotlin/fir/backend/FirIrProvider.kt

@@ -0,0 +1,95 @@
+/*
+ * 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.backend
+
+import org.jetbrains.kotlin.fir.FirSession
+import org.jetbrains.kotlin.fir.containingClass
+import org.jetbrains.kotlin.fir.declarations.*
+import org.jetbrains.kotlin.fir.resolve.providers.symbolProvider
+import org.jetbrains.kotlin.fir.symbols.SymbolInternals
+import org.jetbrains.kotlin.ir.declarations.IrClass
+import org.jetbrains.kotlin.ir.declarations.IrDeclaration
+import org.jetbrains.kotlin.ir.declarations.IrDeclarationParent
+import org.jetbrains.kotlin.ir.linkage.IrProvider
+import org.jetbrains.kotlin.ir.symbols.*
+import org.jetbrains.kotlin.ir.util.IdSignature
+import org.jetbrains.kotlin.name.ClassId
+import org.jetbrains.kotlin.name.FqName
+import org.jetbrains.kotlin.name.Name
+
+@OptIn(SymbolInternals::class)
+class FirIrProvider(val fir2IrComponents: Fir2IrComponents) : IrProvider {
+    private val symbolProvider = fir2IrComponents.session.symbolProvider
+
+    override fun getDeclaration(symbol: IrSymbol): IrDeclaration? {
+        val declarationStorage = fir2IrComponents.declarationStorage
+        val classifierStorage = fir2IrComponents.classifierStorage
+
+        val signature = symbol.signature ?: return null
+
+        val commonSignature = when(signature) {
+            is IdSignature.CommonSignature -> signature
+            is IdSignature.AccessorSignature -> signature.accessorSignature
+            else ->
+                TODO("Unknown signature type")
+        }
+
+        val packageFqName = FqName(commonSignature.packageFqName)
+        val nameSegments = commonSignature.nameSegments
+        val topName = Name.identifier(nameSegments[0])
+
+        val packageFragment = declarationStorage.getIrExternalPackageFragment(packageFqName)
+
+        val firCandidates: List<FirDeclaration>
+        val parent: IrDeclarationParent
+        if (nameSegments.size == 1 && symbol !is IrClassSymbol) {
+            firCandidates = symbolProvider.getTopLevelCallableSymbols(packageFqName, topName).map { it.fir }
+            parent = packageFragment // TODO: need to insert file facade class on JVM
+        } else {
+            var firParentClass: FirRegularClass? = null
+            var firClass = symbolProvider.getClassLikeSymbolByClassId(ClassId(packageFqName, topName))?.fir as? FirRegularClass ?: return null
+            val midSegments = if (symbol is IrClassSymbol) nameSegments.drop(1) else nameSegments.drop(1).dropLast(1)
+            for (midName in midSegments) {
+                firParentClass = firClass
+                firClass = firClass.declarations.singleOrNull { (it as? FirRegularClass)?.name?.asString() == midName } as? FirRegularClass
+                    ?: return null
+            }
+            if (symbol is IrClassSymbol) {
+                firCandidates = listOf(firClass)
+                parent = classifierStorage.getIrClassSymbol(firParentClass!!.symbol).owner
+            } else {
+                val lastName = nameSegments.last()
+                firCandidates = firClass.declarations.filter { it is FirCallableDeclaration && it.symbol.name.asString() == lastName }
+                parent = firParentClass?.let { classifierStorage.getIrClassSymbol(it.symbol).owner } ?: packageFragment
+            }
+        }
+
+        // The next line should have singleOrNull, but in some cases we get multiple references to the same FIR declaration.
+        val firDeclaration = firCandidates.firstOrNull { fir2IrComponents.signatureComposer.composeSignature(it) == signature }
+            ?: return null
+
+        return when (symbol) {
+            is IrClassSymbol -> classifierStorage.getIrClassSymbol((firDeclaration as FirRegularClass).symbol).owner
+            is IrConstructorSymbol -> {
+                val firConstructor = firDeclaration as FirConstructor
+                declarationStorage.getOrCreateIrConstructor(firConstructor, parent as IrClass)
+            }
+            is IrSimpleFunctionSymbol -> {
+                val firSimpleFunction = firDeclaration as FirSimpleFunction
+                declarationStorage.getOrCreateIrFunction(firSimpleFunction, parent)
+            }
+            is IrPropertySymbol -> {
+                val firProperty = firDeclaration as FirProperty
+                declarationStorage.getOrCreateIrProperty(firProperty, parent)
+            }
+            is IrFieldSymbol -> {
+                val firField = firDeclaration as FirField
+                declarationStorage.getOrCreateIrPropertyByPureField(firField, parent)
+            }
+            else -> error("Don't know how to deal with this symbol kind: $symbol")
+        }
+    }
+}