[KAPT] KT-64389 Fix stub generation with generic type constraints

plugins/kapt4/src/org/jetbrains/kotlin/kapt4/StubGenerator.kt

@@ -437,7 +437,7 @@ private class StubGenerator(
                     printWithNoIndent(param.name, " extends ")
                     if (param.extendsListTypes.isNotEmpty()) {
                         param.extendsListTypes.forEachIndexed { i, t ->
-                            if (i > 0) printWithNoIndent(", ")
+                            if (i > 0) printWithNoIndent(" & ")
                             printType(t)
                         }
                     } else {

plugins/kapt4/tests-gen/org/jetbrains/kotlin/kapt4/KotlinKapt4ContextTestGenerated.java

@@ -571,6 +571,12 @@ public class KotlinKapt4ContextTestGenerated extends AbstractKotlinKapt4ContextT
         runTest("plugins/kapt4/../kapt3/kapt3-compiler/testData/converter/multifileClassDefaultPackage.kt");
     }
 
+    @Test
+    @TestMetadata("multipleTypeConstraints.kt")
+    public void testMultipleTypeConstraints() throws Exception {
+        runTest("plugins/kapt4/../kapt3/kapt3-compiler/testData/converter/multipleTypeConstraints.kt");
+    }
+
     @Test
     @TestMetadata("nestedClasses.kt")
     public void testNestedClasses() throws Exception {