ExtractDependencies: more robust cycle check

Checking for seen types alone wasn't robust enough since the cycle might
involve a type`=:=` but not `eq` to a type we've already seen.

Fixes #13575.

Author: smarter

compiler/src/dotty/tools/dotc/sbt/ExtractDependencies.scala

@@ -447,18 +447,20 @@ private class ExtractDependenciesCollector extends tpd.TreeTraverser { thisTreeT
   private abstract class TypeDependencyTraverser(using Context) extends TypeTraverser() {
     protected def addDependency(symbol: Symbol): Unit
 
-    val seen = new mutable.HashSet[Type]
+    // Avoid cycles by remembering both the types (testcase:
+    // tests/run/enum-values.scala) and the symbols of named types (testcase:
+    // tests/pos-java-interop/i13575) we've seen before.
+    val seen = new mutable.HashSet[Symbol | Type]
     def traverse(tp: Type): Unit = if (!seen.contains(tp)) {
       seen += tp
       tp match {
         case tp: NamedType =>
           val sym = tp.symbol
-          if (!sym.is(Package)) {
+          if !seen.contains(sym) && !sym.is(Package) then
+            seen += sym
             addDependency(sym)
-            if (!sym.isClass)
-              traverse(tp.info)
+            if !sym.isClass then traverse(tp.info)
             traverse(tp.prefix)
-          }
         case tp: ThisType =>
           traverse(tp.underlying)
         case tp: ConstantType =>

tests/pos-java-interop/i13575/Builder.java

@@ -0,0 +1,16 @@
+package com.lamoroso.example;
+
+import java.util.Collections;
+import java.util.List;
+
+public abstract class Builder<T extends Builder<T, R>, R> {
+
+    private List<String> pools;
+
+    public Builder<T, R> withPool(String... pools) {
+        Collections.addAll(this.pools, pools);
+        return this;
+    }
+
+    public Builder<T, R> build(){return null;}
+}

tests/pos-java-interop/i13575/Client.java

@@ -0,0 +1,9 @@
+package com.lamoroso.example;
+
+public class Client {
+    
+    public static Builder<?, ?> builder() {
+        return null;
+    }
+    
+}

tests/pos-java-interop/i13575/RestClient.java

@@ -0,0 +1,15 @@
+package com.lamoroso.example;
+
+public class RestClient {
+
+    private Object instance;
+
+    public RestClient(Object instance) {
+        this.instance = instance;
+    }
+
+    public static RestClientBuilder<?,?> builder() {
+        return new RestClientBuilder();
+    }
+    
+}

tests/pos-java-interop/i13575/RestClientBuilder.java

@@ -0,0 +1,19 @@
+package com.lamoroso.example;
+
+public class RestClientBuilder<T extends Builder<T, R>, R> {
+
+    private Builder<?, ?> wrappedBuilder;
+
+    protected RestClientBuilder() {
+        this.wrappedBuilder = Client.builder();
+    }
+    
+    public RestClientBuilder<T, R> withPool(String... pools) {
+        this.wrappedBuilder.withPool(pools);
+        return this;
+    }
+
+    public RestClient build() {
+        return new RestClient(wrappedBuilder.build());
+    }
+}

tests/pos-java-interop/i13575/ScalaApp.scala

@@ -0,0 +1,5 @@
+package com.lamoroso.example
+
+object ScalaApp extends App {
+  RestClient.builder().withPool("hello").build()
+}