FIR: move FirModifierList to module 'fir:checkers'

To remove dependency of a large module 'fir:tree' on 'psi', allowing
them to compile in parallel.

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

@@ -0,0 +1,86 @@
+/*
+ * Copyright 2010-2020 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
+
+import com.intellij.lang.ASTNode
+import com.intellij.lang.LighterASTNode
+import com.intellij.openapi.util.Ref
+import com.intellij.psi.PsiElement
+import com.intellij.psi.tree.TokenSet
+import com.intellij.util.diff.FlyweightCapableTreeStructure
+import org.jetbrains.kotlin.KtNodeTypes
+import org.jetbrains.kotlin.fir.*
+import org.jetbrains.kotlin.lexer.KtModifierKeywordToken
+import org.jetbrains.kotlin.lexer.KtTokens
+import org.jetbrains.kotlin.psi.KtModifierList
+import org.jetbrains.kotlin.psi.KtModifierListOwner
+
+sealed class FirModifierList {
+    abstract val modifiers: List<FirModifier<*>>
+}
+
+fun FirSourceElement?.getModifierList(): FirModifierList? {
+    return when (this) {
+        null -> null
+        is FirPsiSourceElement<*> -> (psi as? KtModifierListOwner)?.modifierList?.let { FirPsiModifierList(it) }
+        is FirLightSourceElement -> {
+            val kidsRef = Ref<Array<LighterASTNode?>>()
+            tree.getChildren(element, kidsRef)
+            val modifierListNode = kidsRef.get().find { it?.tokenType == KtNodeTypes.MODIFIER_LIST } ?: return null
+            FirLightModifierList(modifierListNode, tree)
+        }
+    }
+}
+
+private val MODIFIER_KEYWORD_SET = TokenSet.orSet(KtTokens.SOFT_KEYWORDS, TokenSet.create(KtTokens.IN_KEYWORD, KtTokens.FUN_KEYWORD))
+
+class FirPsiModifierList(val modifierList: KtModifierList) : FirModifierList() {
+    override val modifiers: List<FirPsiModifier>
+        get() = modifierList.node.getChildren(MODIFIER_KEYWORD_SET).map { node ->
+            FirPsiModifier(node, node.elementType as KtModifierKeywordToken)
+        }
+
+}
+
+class FirLightModifierList(val modifierList: LighterASTNode, val tree: FlyweightCapableTreeStructure<LighterASTNode>) : FirModifierList() {
+    override val modifiers: List<FirLightModifier>
+        get() {
+            val kidsRef = Ref<Array<LighterASTNode?>>()
+            tree.getChildren(modifierList, kidsRef)
+            val modifierNodes = kidsRef.get()
+            return modifierNodes.filterNotNull()
+                .filter { it.tokenType is KtModifierKeywordToken }
+                .map { FirLightModifier(it, it.tokenType as KtModifierKeywordToken, tree) }
+        }
+}
+
+sealed class FirModifier<Node : Any>(val node: Node, val token: KtModifierKeywordToken)
+
+class FirPsiModifier(
+    node: ASTNode,
+    token: KtModifierKeywordToken
+) : FirModifier<ASTNode>(node, token)
+
+class FirLightModifier(
+    node: LighterASTNode,
+    token: KtModifierKeywordToken,
+    val tree: FlyweightCapableTreeStructure<LighterASTNode>
+) : FirModifier<LighterASTNode>(node, token)
+
+val FirModifier<*>.psi: PsiElement? get() = (this as? FirPsiModifier)?.node?.psi
+
+val FirModifier<*>.lightNode: LighterASTNode? get() = (this as? FirLightModifier)?.node
+
+val FirModifier<*>.source: FirSourceElement?
+    get() = when (this) {
+        is FirPsiModifier -> this.psi?.toFirPsiSourceElement()
+        is FirLightModifier -> {
+            // TODO pretty sure I got offsets wrong here
+            val startOffset = tree.getStartOffset(node)
+            val endOffset = tree.getEndOffset(node)
+            node.toFirLightSourceElement(startOffset, endOffset, tree)
+        }
+    }

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

@@ -6,11 +6,18 @@
 package org.jetbrains.kotlin.fir.analysis.checkers.declaration
 
 import org.jetbrains.kotlin.KtNodeTypes
-import org.jetbrains.kotlin.fir.*
+import org.jetbrains.kotlin.fir.FirSourceElement
+import org.jetbrains.kotlin.fir.analysis.checkers.FirModifier
+import org.jetbrains.kotlin.fir.analysis.checkers.FirModifierList
 import org.jetbrains.kotlin.fir.analysis.checkers.context.CheckerContext
+import org.jetbrains.kotlin.fir.analysis.checkers.getModifierList
+import org.jetbrains.kotlin.fir.analysis.checkers.source
 import org.jetbrains.kotlin.fir.analysis.diagnostics.DiagnosticReporter
 import org.jetbrains.kotlin.fir.analysis.diagnostics.FirErrors
-import org.jetbrains.kotlin.fir.declarations.*
+import org.jetbrains.kotlin.fir.declarations.FirClass
+import org.jetbrains.kotlin.fir.declarations.FirDeclaration
+import org.jetbrains.kotlin.fir.declarations.FirProperty
+import org.jetbrains.kotlin.fir.declarations.FirValueParameter
 import org.jetbrains.kotlin.fir.declarations.impl.FirDefaultPropertyAccessor
 import org.jetbrains.kotlin.lexer.KtModifierKeywordToken
 import org.jetbrains.kotlin.lexer.KtTokens.*
@@ -195,5 +202,4 @@ object FirModifierChecker : FirDeclarationChecker<FirDeclaration>() {
         val source = modifier.source
         source?.let { report(FirErrors.INCOMPATIBLE_MODIFIERS.on(it, firstKeyword, secondKeyword)) }
     }
-
-}
+}