FIR IDE: implement completion in where clause

idea/idea-fir/src/org/jetbrains/kotlin/idea/completion/KotlinFirCompletionContributor.kt

@@ -69,6 +69,7 @@ private object KotlinFirCompletionProvider : CompletionProvider<CompletionParame
         val annotationsContributor = FirAnnotationCompletionContributor(basicContext)
         val packageCompletionContributor = FirPackageCompletionContributor(basicContext)
         val importDirectivePackageMembersCompletionContributor = FirImportDirectivePackageMembersCompletionContributor(basicContext)
+        val typeParameterConstraintNameInWhereClauseContributor = FirTypeParameterConstraintNameInWhereClauseCompletionContributor(basicContext)
 
         when (positionContext) {
             is FirExpressionNameReferencePositionContext -> {
@@ -103,6 +104,10 @@ private object KotlinFirCompletionProvider : CompletionProvider<CompletionParame
                 complete(packageCompletionContributor, positionContext)
             }
 
+            is FirTypeConstraintNameInWhereClausePositionContext -> {
+                complete(typeParameterConstraintNameInWhereClauseContributor, positionContext)
+            }
+
             is FirUnknownPositionContext -> {
                 complete(keywordContributor, positionContext)
             }

idea/idea-fir/src/org/jetbrains/kotlin/idea/completion/context/FirPositionCompletionContext.kt

@@ -19,6 +19,11 @@ internal sealed class FirRawPositionCompletionContext {
     abstract val position: PsiElement
 }
 
+internal class FirTypeConstraintNameInWhereClausePositionContext(
+    override val position: PsiElement,
+    val typeParametersOwner: KtTypeParameterListOwner
+) : FirRawPositionCompletionContext()
+
 internal sealed class FirNameReferencePositionContext : FirRawPositionCompletionContext() {
     abstract val reference: KtSimpleNameReference
     abstract val nameExpression: KtSimpleNameExpression
@@ -40,7 +45,6 @@ internal class FirPackageDirectivePositionContext(
 ) : FirNameReferencePositionContext()
 
 
-
 internal class FirTypeNameReferencePositionContext(
     override val position: PsiElement,
     override val reference: KtSimpleNameReference,
@@ -108,6 +112,10 @@ internal object FirPositionCompletionContextDetector {
                     explicitReceiver,
                 )
             }
+            parent is KtTypeConstraint -> FirTypeConstraintNameInWhereClausePositionContext(
+                position,
+                position.parentOfType()!!,
+            )
             else -> {
                 FirExpressionNameReferencePositionContext(position, reference, nameExpression, explicitReceiver)
             }
@@ -169,7 +177,10 @@ internal object FirPositionCompletionContextDetector {
                 positionContext.nameExpression,
                 action
             )
-            is FirUnknownPositionContext, is FirImportDirectivePositionContext, is FirPackageDirectivePositionContext -> {
+            is FirUnknownPositionContext,
+            is FirImportDirectivePositionContext,
+            is FirPackageDirectivePositionContext,
+            is FirTypeConstraintNameInWhereClausePositionContext -> {
                 analyse(basicContext.originalKtFile, action)
             }
         }

idea/idea-fir/src/org/jetbrains/kotlin/idea/completion/contributors/FirKeywordCompletionContributor.kt

@@ -9,9 +9,11 @@ import com.intellij.codeInsight.lookup.LookupElement
 import com.intellij.openapi.module.Module
 import com.intellij.psi.PsiElement
 import org.jetbrains.kotlin.idea.completion.*
+import org.jetbrains.kotlin.idea.completion.context.*
 import org.jetbrains.kotlin.idea.completion.context.FirBasicCompletionContext
 import org.jetbrains.kotlin.idea.completion.context.FirNameReferencePositionContext
 import org.jetbrains.kotlin.idea.completion.context.FirRawPositionCompletionContext
+import org.jetbrains.kotlin.idea.completion.context.FirTypeConstraintNameInWhereClausePositionContext
 import org.jetbrains.kotlin.idea.completion.context.FirUnknownPositionContext
 import org.jetbrains.kotlin.idea.completion.contributors.keywords.OverrideKeywordHandler
 import org.jetbrains.kotlin.idea.completion.contributors.keywords.ReturnKeywordHandler
@@ -44,6 +46,9 @@ internal class FirKeywordCompletionContributor(basicContext: FirBasicCompletionC
                     else -> reference.expression
                 }
             }
+            is FirTypeConstraintNameInWhereClausePositionContext -> {
+                error("keyword completion should not be called for FirTypeConstraintNameInWhereClausePositionContext")
+            }
             is FirUnknownPositionContext -> null
         }
         completeWithResolve(expression ?: positionContext.position, expression)

idea/idea-fir/src/org/jetbrains/kotlin/idea/completion/contributors/FirTypeParameterConstraintNameInWhereClauseCompletionContributor.kt

@@ -0,0 +1,54 @@
+/*
+ * 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.idea.completion.contributors
+
+import com.intellij.codeInsight.completion.InsertHandler
+import com.intellij.codeInsight.completion.InsertionContext
+import com.intellij.codeInsight.lookup.LookupElement
+import com.intellij.codeInsight.lookup.LookupElementBuilder
+import org.jetbrains.kotlin.idea.completion.KotlinFirIconProvider.getIconFor
+import org.jetbrains.kotlin.idea.completion.context.FirBasicCompletionContext
+import org.jetbrains.kotlin.idea.completion.context.FirTypeConstraintNameInWhereClausePositionContext
+import org.jetbrains.kotlin.idea.completion.contributors.helpers.addSymbolAndInvokeCompletion
+import org.jetbrains.kotlin.idea.completion.lookups.KotlinLookupObject
+import org.jetbrains.kotlin.idea.frontend.api.KtAnalysisSession
+import org.jetbrains.kotlin.idea.frontend.api.symbols.markers.KtSymbolWithTypeParameters
+import org.jetbrains.kotlin.name.Name
+import org.jetbrains.kotlin.renderer.render
+
+internal class FirTypeParameterConstraintNameInWhereClauseCompletionContributor(
+    basicContext: FirBasicCompletionContext
+) : FirCompletionContributorBase<FirTypeConstraintNameInWhereClausePositionContext>(basicContext) {
+
+    override fun KtAnalysisSession.complete(positionContext: FirTypeConstraintNameInWhereClausePositionContext) {
+        val ownerSymbol = positionContext.typeParametersOwner.getSymbol() as? KtSymbolWithTypeParameters ?: return
+        ownerSymbol.typeParameters.forEach { typeParameter ->
+            val name = typeParameter.name
+            val icon = getIconFor(typeParameter)
+            LookupElementBuilder.create(TypeParameterInWhenClauseILookupObject(name), name.asString())
+                .withTailText(" : ")
+                .withInsertHandler(TypeParameterInWhenClauseInsertionHandler)
+                .withPsiElement(typeParameter.psi)
+                .withIcon(icon)
+                .let(result::addElement)
+        }
+    }
+}
+
+private class TypeParameterInWhenClauseILookupObject(override val shortName: Name) : KotlinLookupObject
+
+
+private object TypeParameterInWhenClauseInsertionHandler : InsertHandler<LookupElement> {
+    override fun handleInsert(context: InsertionContext, item: LookupElement) {
+        val lookupElement = item.`object` as TypeParameterInWhenClauseILookupObject
+        val name = lookupElement.shortName.render()
+        context.document.replaceString(context.startOffset, context.tailOffset, name)
+        context.commitDocument()
+        context.addSymbolAndInvokeCompletion(symbol = " : ")
+    }
+}
+
+

idea/idea-fir/src/org/jetbrains/kotlin/idea/completion/contributors/helpers/FirSuperEntriesProvider.kt

@@ -34,7 +34,7 @@ internal object SuperCallInsertionHandler : InsertHandler<LookupElement> {
         val lookupObject = item.`object` as SuperCallLookupObject
 
         replaceWithClassIdAndShorten(lookupObject, context)
-        context.addDotAndInvokeCompletion()
+        context.addSymbolAndInvokeCompletion(symbol = ".")
     }
 
     private fun replaceWithClassIdAndShorten(

idea/idea-fir/src/org/jetbrains/kotlin/idea/completion/contributors/helpers/completionHelpers.kt

@@ -10,8 +10,8 @@ import com.intellij.codeInsight.completion.CompletionType
 import com.intellij.codeInsight.completion.InsertionContext
 import com.intellij.openapi.application.ApplicationManager
 
-internal fun InsertionContext.addDotAndInvokeCompletion() {
+internal fun InsertionContext.addSymbolAndInvokeCompletion(symbol: String) {
-    addDotToCompletion(this)
+    addSymbolToCompletion(this, symbol)
     invokeCompletion(this)
 }
 
@@ -22,8 +22,8 @@ private fun invokeCompletion(context: InsertionContext) {
     }
 }
 
-private fun addDotToCompletion(context: InsertionContext) {
+private fun addSymbolToCompletion(context: InsertionContext, symbol: String) {
-    context.document.insertString(context.tailOffset, ".")
+    context.document.insertString(context.tailOffset, symbol)
     context.commitDocument()
     context.editor.caretModel.moveToOffset(context.tailOffset)
 }

idea/idea-fir/src/org/jetbrains/kotlin/idea/completion/lookups/factories/PackagePartLookupElementFactory.kt

@@ -10,7 +10,7 @@ import com.intellij.codeInsight.completion.InsertionContext
 import com.intellij.codeInsight.lookup.LookupElement
 import com.intellij.codeInsight.lookup.LookupElementBuilder
 import com.intellij.icons.AllIcons
-import org.jetbrains.kotlin.idea.completion.contributors.helpers.addDotAndInvokeCompletion
+import org.jetbrains.kotlin.idea.completion.contributors.helpers.addSymbolAndInvokeCompletion
 import org.jetbrains.kotlin.idea.completion.lookups.KotlinLookupObject
 import org.jetbrains.kotlin.miniStdLib.letIf
 import org.jetbrains.kotlin.name.FqName
@@ -41,7 +41,7 @@ private object PackagePartInsertionHandler : InsertHandler<LookupElement> {
         val name = lookupElement.shortName.render()
         context.document.replaceString(context.startOffset, context.tailOffset, name)
         context.commitDocument()
-        context.addDotAndInvokeCompletion()
+        context.addSymbolAndInvokeCompletion(symbol = ".")
     }
 }