From e10cf7c2449fadeadeaba50741feb30c1a5b8b08 Mon Sep 17 00:00:00 2001
From: nabiljarrai <nabil.jarrai.work@gmail.com>
Date: Mon, 9 Mar 2026 05:17:42 +0400
Subject: [PATCH] Reuse cached erased TypeMirrors for Collection/Map/Stream
 checks in Type

The private isCollection(), isMap(), and isStream() methods in Type were
redundantly resolving TypeElements and erasing them on every call inside
getAlternativeTargetAccessors(). TypeFactory already caches these exact
erased TypeMirrors at construction time, so I exposed them via package-private
getters and rewired Type to use them directly. Removed the now-unused
isSubType helper method.
---
 .../mapstruct/ap/internal/model/common/Type.java   | 14 +++-----------
 .../ap/internal/model/common/TypeFactory.java      | 12 ++++++++++++
 2 files changed, 15 insertions(+), 11 deletions(-)

diff --git a/processor/src/main/java/org/mapstruct/ap/internal/model/common/Type.java b/processor/src/main/java/org/mapstruct/ap/internal/model/common/Type.java
index f742e1ba..d29e545f 100644
--- a/processor/src/main/java/org/mapstruct/ap/internal/model/common/Type.java
+++ b/processor/src/main/java/org/mapstruct/ap/internal/model/common/Type.java
@@ -44,7 +44,6 @@
 import org.mapstruct.ap.internal.util.ElementUtils;
 import org.mapstruct.ap.internal.util.Executables;
 import org.mapstruct.ap.internal.util.Filters;
-import org.mapstruct.ap.internal.util.JavaStreamConstants;
 import org.mapstruct.ap.internal.util.NativeTypes;
 import org.mapstruct.ap.internal.util.Nouns;
 import org.mapstruct.ap.internal.util.TypeUtils;
@@ -1084,23 +1083,16 @@ private boolean isCollectionOrMapOrStream(Accessor getterMethod) {
     }
 
     private boolean isCollection(TypeMirror candidate) {
-        return isSubType( candidate, Collection.class );
+        return typeUtils.isSubtypeErased( candidate, typeFactory.getCollectionType() );
     }
 
     private boolean isStream(TypeMirror candidate) {
-        TypeElement streamTypeElement = elementUtils.getTypeElement( JavaStreamConstants.STREAM_FQN );
-        TypeMirror streamType = streamTypeElement == null ? null : typeUtils.erasure( streamTypeElement.asType() );
+        TypeMirror streamType = typeFactory.getStreamType();
         return streamType != null && typeUtils.isSubtypeErased( candidate, streamType );
     }
 
     private boolean isMap(TypeMirror candidate) {
-        return isSubType( candidate, Map.class );
-    }
-
-    private boolean isSubType(TypeMirror candidate, Class<?> clazz) {
-        String className = clazz.getCanonicalName();
-        TypeMirror classType = typeUtils.erasure( elementUtils.getTypeElement( className ).asType() );
-        return typeUtils.isSubtypeErased( candidate, classType );
+        return typeUtils.isSubtypeErased( candidate, typeFactory.getMapType() );
     }
 
     /**
diff --git a/processor/src/main/java/org/mapstruct/ap/internal/model/common/TypeFactory.java b/processor/src/main/java/org/mapstruct/ap/internal/model/common/TypeFactory.java
index f28e0c68..6eeddaaa 100644
--- a/processor/src/main/java/org/mapstruct/ap/internal/model/common/TypeFactory.java
+++ b/processor/src/main/java/org/mapstruct/ap/internal/model/common/TypeFactory.java
@@ -693,6 +693,18 @@ public BuilderType builderTypeFor( Type type, BuilderGem builder ) {
         return null;
     }
 
+    TypeMirror getCollectionType() {
+        return collectionType;
+    }
+
+    TypeMirror getMapType() {
+        return mapType;
+    }
+
+    TypeMirror getStreamType() {
+        return streamType;
+    }
+
     public Type effectiveResultTypeFor( Type type, BuilderGem builder ) {
         if ( type != null ) {
             BuilderInfo builderInfo = findBuilder( type.getTypeMirror(), builder, false );