From df3e562962ba5e58ed598f94afaa9bab3e02b86b Mon Sep 17 00:00:00 2001
From: Zac Sweers <zac.sweers@gmail.com>
Date: Tue, 11 Jun 2024 17:05:26 -0400
Subject: [PATCH] Fix complex alias handling in KsTypes (#1929)

---
 docs/changelog.md                             |  1 +
 .../com/squareup/kotlinpoet/ksp/KsTypes.kt    |  2 +-
 .../ksp/test/processor/TestProcessorTest.kt   | 43 +++++++++++++++++++
 3 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/docs/changelog.md b/docs/changelog.md
index 34ec2231dc..c0c33f0b7d 100644
--- a/docs/changelog.md
+++ b/docs/changelog.md
@@ -5,6 +5,7 @@ Change Log
 
 * **Fix**: Don't expand typealiases of function types to `LambdaTypeName`s in `KSTypeReference.toTypeName()`.
 * **Fix**: Small double and float values were set to 0.0 in %L translation (#1919)
+* **Fix**: Fix typealias type argument resolution in KSP2.
 * **Enhancement**: Make enum entry references in `KSAnnotation.toAnnotationSpec()` and `KSClassDeclaration.toClassName()` more robust.
 * Migrate `kotlinpoet-metadata` to stable `org.jetbrains.kotlin:kotlin-metadata-jvm` artifact for Metadata parsing.
 * Promote `kotlinpoet-metadata` out of preview to stable.
diff --git a/interop/ksp/src/main/kotlin/com/squareup/kotlinpoet/ksp/KsTypes.kt b/interop/ksp/src/main/kotlin/com/squareup/kotlinpoet/ksp/KsTypes.kt
index 19e48c01a3..500cb62aac 100644
--- a/interop/ksp/src/main/kotlin/com/squareup/kotlinpoet/ksp/KsTypes.kt
+++ b/interop/ksp/src/main/kotlin/com/squareup/kotlinpoet/ksp/KsTypes.kt
@@ -199,6 +199,6 @@ public fun KSTypeReference.toTypeName(
       returnType = elem.returnType.toTypeName(typeParamResolver),
     ).copy(nullable = type.isMarkedNullable, suspending = type.isSuspendFunctionType)
   } else {
-    type.toTypeName(typeParamResolver, element?.typeArguments.orEmpty())
+    type.toTypeName(typeParamResolver, type.arguments)
   }
 }
diff --git a/interop/ksp/test-processor/src/test/kotlin/com/squareup/kotlinpoet/ksp/test/processor/TestProcessorTest.kt b/interop/ksp/test-processor/src/test/kotlin/com/squareup/kotlinpoet/ksp/test/processor/TestProcessorTest.kt
index 640012a3c1..966aca095a 100644
--- a/interop/ksp/test-processor/src/test/kotlin/com/squareup/kotlinpoet/ksp/test/processor/TestProcessorTest.kt
+++ b/interop/ksp/test-processor/src/test/kotlin/com/squareup/kotlinpoet/ksp/test/processor/TestProcessorTest.kt
@@ -911,6 +911,49 @@ class TestProcessorTest(private val useKsp2: Boolean) {
     )
   }
 
+  @Test
+  fun complexAliasing() {
+    val compilation = prepareCompilation(
+      kotlin(
+        "Example.kt",
+        """
+           package test
+
+           import javax.inject.Provider
+           import com.squareup.kotlinpoet.ksp.test.processor.ExampleAnnotation
+
+           typealias DaggerProvider<T> = @JvmSuppressWildcards Provider<T>
+           interface SelectOptions
+           interface SelectHandler<T>
+
+           @ExampleAnnotation
+           class Example(
+             private val handlers: Map<Class<out SelectOptions>, DaggerProvider<SelectHandler<*>>>,
+           )
+           """,
+      ),
+    )
+
+    val result = compilation.compile()
+    assertThat(result.exitCode).isEqualTo(KotlinCompilation.ExitCode.OK)
+    val generatedFileText = File(compilation.kspSourcesDir, "kotlin/test/TestExample.kt")
+      .readText()
+
+    assertThat(generatedFileText).isEqualTo(
+      """
+        package test
+
+        import java.lang.Class
+        import kotlin.collections.Map
+
+        public class TestExample {
+          private val handlers: Map<Class<out SelectOptions>, DaggerProvider<SelectHandler<*>>> = TODO()
+        }
+
+      """.trimIndent(),
+    )
+  }
+
   private fun prepareCompilation(vararg sourceFiles: SourceFile): KotlinCompilation {
     return KotlinCompilation()
       .apply {