From d5933f28abf76bff729b8fad5c351c279f06b1c3 Mon Sep 17 00:00:00 2001
From: Marco Pennekamp <marco.pennekamp@jetbrains.com>
Date: Wed, 1 Mar 2023 16:54:17 +0100
Subject: [PATCH] [AA] KT-56617 Optimize type parameter access for Java class
 symbols

- Completion accesses symbol type parameters to render their names.
  Instead of building the whole list of type parameters, and
  consequently the whole FIR class, completion can now access the type
  parameter names directly.
---
 .../api/fir/symbols/KtFirPsiJavaClassSymbol.kt      | 13 ++++++++++++-
 .../kotlin/analysis/api/symbols/markers/markers.kt  |  9 ++++++++-
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/symbols/KtFirPsiJavaClassSymbol.kt b/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/symbols/KtFirPsiJavaClassSymbol.kt
index 0449be14a43..5d9e04816ce 100644
--- a/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/symbols/KtFirPsiJavaClassSymbol.kt
+++ b/analysis/analysis-api-fir/src/org/jetbrains/kotlin/analysis/api/fir/symbols/KtFirPsiJavaClassSymbol.kt
@@ -97,6 +97,16 @@ internal class KtFirPsiJavaClassSymbol(
             psi.containingClass?.let { KtFirPsiJavaClassSymbol(it, analysisSession) }
         }
 
+    override val typeParameterNames: List<Name> by cached {
+        // The parent Java class might contribute `FirOuterClassTypeParameterRef`s to the FIR class's type parameters (see
+        // `FirJavaFacade.createFirJavaClass`), but since they are filtered out by `createRegularKtTypeParameters`, we do not need to
+        // include them in the list of type parameter names.
+        javaClass.typeParameters.map { it.name }
+    }
+
+    val hasTypeParameters: Boolean
+        get() = withValidityAssertion { javaClass.typeParameters.isNotEmpty() }
+
     override val isData: Boolean get() = withValidityAssertion { false }
     override val isInline: Boolean get() = withValidityAssertion { false }
     override val isFun: Boolean get() = withValidityAssertion { false }
@@ -137,7 +147,8 @@ internal class KtFirPsiJavaClassSymbol(
     }
 
     override val typeParameters: List<KtTypeParameterSymbol> by cached {
-        firSymbol.createRegularKtTypeParameters(builder)
+        if (hasTypeParameters) firSymbol.createRegularKtTypeParameters(builder)
+        else emptyList()
     }
 
     override val annotationsList: KtAnnotationsList by cached {
diff --git a/analysis/analysis-api/src/org/jetbrains/kotlin/analysis/api/symbols/markers/markers.kt b/analysis/analysis-api/src/org/jetbrains/kotlin/analysis/api/symbols/markers/markers.kt
index 67814566750..321ef93f22e 100644
--- a/analysis/analysis-api/src/org/jetbrains/kotlin/analysis/api/symbols/markers/markers.kt
+++ b/analysis/analysis-api/src/org/jetbrains/kotlin/analysis/api/symbols/markers/markers.kt
@@ -5,9 +5,9 @@
 
 package org.jetbrains.kotlin.analysis.api.symbols.markers
 
+import org.jetbrains.kotlin.analysis.api.lifetime.withValidityAssertion
 import org.jetbrains.kotlin.analysis.api.symbols.KtSymbol
 import org.jetbrains.kotlin.analysis.api.symbols.KtTypeParameterSymbol
-import org.jetbrains.kotlin.analysis.api.types.KtType
 import org.jetbrains.kotlin.name.Name
 
 public interface KtPossiblyNamedSymbol : KtSymbol {
@@ -20,4 +20,11 @@ public interface KtNamedSymbol : KtPossiblyNamedSymbol {
 
 public interface KtSymbolWithTypeParameters : KtSymbol {
     public val typeParameters: List<KtTypeParameterSymbol>
+
+    /**
+     * The names of [typeParameters]. Using this property should be preferred if only the names of type parameters are needed, because some
+     * symbol implementations may avoid building the full list of type parameters.
+     */
+    public val typeParameterNames: List<Name>
+        get() = withValidityAssertion { typeParameters.map { it.name } }
 }
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