FIR Completion: Add simple lookup decorating with icon and parameters

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/completion/HighLevelApiLookupElementFactory.kt

@@ -0,0 +1,60 @@
+/*
+ * 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.idea.completion
+
+import com.intellij.codeInsight.lookup.LookupElement
+import com.intellij.codeInsight.lookup.LookupElementBuilder
+import org.jetbrains.kotlin.idea.frontend.api.symbols.*
+import org.jetbrains.kotlin.idea.frontend.api.types.KtDenotableType
+import org.jetbrains.kotlin.idea.frontend.api.types.KtType
+
+internal class HighLevelApiLookupElementFactory {
+    private val classLookupElementFactory = ClassLookupElementFactory()
+    private val variableLookupElementFactory = VariableLookupElementFactory()
+    private val functionLookupElementFactory = FunctionLookupElementFactory()
+
+    fun createLookupElement(symbol: KtNamedSymbol): LookupElement {
+        val elementBuilder = when (symbol) {
+            is KtFunctionSymbol -> functionLookupElementFactory.createLookup(symbol)
+            is KtVariableLikeSymbol -> variableLookupElementFactory.createLookup(symbol)
+            is KtClassLikeSymbol -> classLookupElementFactory.createLookup(symbol)
+            else -> throw IllegalArgumentException("Cannot create a lookup element for $symbol")
+        }
+
+        return elementBuilder.withIcon(KotlinSymbolIconProvider.getIconFor(symbol))
+    }
+}
+
+private class ClassLookupElementFactory {
+    fun createLookup(symbol: KtClassLikeSymbol): LookupElementBuilder {
+        return LookupElementBuilder.create(symbol.name.asString())
+    }
+}
+
+private class VariableLookupElementFactory {
+    fun createLookup(symbol: KtVariableLikeSymbol): LookupElementBuilder {
+        return LookupElementBuilder.create(symbol.name.asString())
+            .withTypeText(ShortNamesRenderer.renderType(symbol.type))
+    }
+}
+
+private class FunctionLookupElementFactory {
+    fun createLookup(symbol: KtFunctionSymbol): LookupElementBuilder {
+        return LookupElementBuilder.create(symbol.name.asString())
+            .appendTailText(ShortNamesRenderer.renderFunctionParameters(symbol), true)
+            .withTypeText(ShortNamesRenderer.renderType(symbol.type))
+    }
+}
+
+
+private object ShortNamesRenderer {
+    fun renderFunctionParameters(function: KtFunctionSymbol): String =
+        function.valueParameters.joinToString(", ", "(", ")") { renderFunctionParameter(it) }
+
+    fun renderType(ktType: KtType): String = (ktType as? KtDenotableType)?.asString() ?: ""
+
+    private fun renderFunctionParameter(param: KtFunctionParameterSymbol) = "${param.name.asString()}: ${renderType(param.type)}"
+}

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

@@ -6,7 +6,6 @@
 package org.jetbrains.kotlin.idea.completion
 
 import com.intellij.codeInsight.completion.*
-import com.intellij.codeInsight.lookup.LookupElementBuilder
 import com.intellij.patterns.PlatformPatterns
 import com.intellij.patterns.PsiJavaPatterns
 import com.intellij.util.ProcessingContext
@@ -27,6 +26,8 @@ class KotlinFirCompletionContributor : CompletionContributor() {
 }
 
 private object KotlinHighLevelApiContributor : CompletionProvider<CompletionParameters>() {
+    private val lookupElementFactory = HighLevelApiLookupElementFactory()
+
     override fun addCompletions(parameters: CompletionParameters, context: ProcessingContext, result: CompletionResultSet) {
         if (shouldSuppressCompletion(parameters, result.prefixMatcher)) return
 
@@ -48,7 +49,7 @@ private object KotlinHighLevelApiContributor : CompletionProvider<CompletionPara
 
         fun addToCompletion(symbol: KtSymbol) {
             if (symbol !is KtNamedSymbol) return
-            result.addElement(LookupElementBuilder.create(symbol.name.asString()))
+            result.addElement(lookupElementFactory.createLookupElement(symbol))
         }
 
         if (possibleReceiverScope != null) {

idea/idea-frontend-fir/src/org/jetbrains/kotlin/idea/completion/KotlinSymbolIconProvider.kt

@@ -0,0 +1,53 @@
+/*
+ * 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.idea.completion
+
+import com.intellij.util.PlatformIcons
+import org.jetbrains.kotlin.idea.KotlinIcons
+import org.jetbrains.kotlin.idea.frontend.api.symbols.*
+import javax.swing.Icon
+
+internal object KotlinSymbolIconProvider {
+    fun getIconFor(symbol: KtNamedSymbol): Icon? {
+        if (symbol is KtFunctionSymbol) {
+            val isAbstract = symbol.modality == KtCommonSymbolModality.ABSTRACT
+
+            return when {
+                symbol.isExtension -> {
+                    if (isAbstract) KotlinIcons.ABSTRACT_EXTENSION_FUNCTION else KotlinIcons.EXTENSION_FUNCTION
+                }
+                symbol.symbolKind == KtSymbolKind.MEMBER -> {
+                    if (isAbstract) PlatformIcons.ABSTRACT_METHOD_ICON else PlatformIcons.METHOD_ICON
+                }
+                else -> KotlinIcons.FUNCTION
+            }
+        }
+
+        if (symbol is KtClassOrObjectSymbol) {
+            val isAbstract = symbol.modality == KtCommonSymbolModality.ABSTRACT
+
+            return when (symbol.classKind) {
+                KtClassKind.CLASS -> if (isAbstract) KotlinIcons.CLASS else KotlinIcons.ABSTRACT_CLASS
+                KtClassKind.ENUM_CLASS, KtClassKind.ENUM_ENTRY -> KotlinIcons.ENUM
+                KtClassKind.ANNOTATION_CLASS -> KotlinIcons.ANNOTATION
+                KtClassKind.OBJECT, KtClassKind.COMPANION_OBJECT -> KotlinIcons.OBJECT
+                KtClassKind.INTERFACE -> KotlinIcons.INTERFACE
+            }
+        }
+
+        if (symbol is KtParameterSymbol) return KotlinIcons.PARAMETER
+
+        if (symbol is KtLocalVariableSymbol) return if (symbol.isVal) KotlinIcons.VAL else KotlinIcons.VAR
+
+        if (symbol is KtPropertySymbol) return if (symbol.isVal) KotlinIcons.FIELD_VAL else KotlinIcons.FIELD_VAR
+
+        if (symbol is KtTypeParameterSymbol) return PlatformIcons.CLASS_ICON
+
+        if (symbol is KtTypeAliasSymbol) return KotlinIcons.TYPE_ALIAS
+
+        return null
+    }
+}