Qualify types masked by type variables (#657)

* Use fully qualified names if a type variable masks a type name, even if it is in the same package

* Add a makeshift multiset to handle https://github.com/square/javapoet/pull/657\#discussion_r205514292

3 files changed, 38 insertions, 1 deletions

diff --git a/src/main/java/com/squareup/javapoet/CodeWriter.java b/src/main/java/com/squareup/javapoet/CodeWriter.java
index 542f434..ac8178f 100644
--- a/src/main/java/com/squareup/javapoet/CodeWriter.java
+++ b/src/main/java/com/squareup/javapoet/CodeWriter.java
@@ -57,6 +57,7 @@ final class CodeWriter {
   private final Map<String, ClassName> importedTypes;
   private final Map<String, ClassName> importableTypes = new LinkedHashMap<>();
   private final Set<String> referencedNames = new LinkedHashSet<>();
+  private final Multiset<String> currentTypeVariables = new Multiset<>();
   private boolean trailingNewline;
 
   /**
@@ -187,6 +188,8 @@ final class CodeWriter {
   public void emitTypeVariables(List<TypeVariableName> typeVariables) throws IOException {
     if (typeVariables.isEmpty()) return;
 
+    typeVariables.forEach(typeVariable -> currentTypeVariables.add(typeVariable.name));
+
     emit("<");
     boolean firstTypeVariable = true;
     for (TypeVariableName typeVariable : typeVariables) {
@@ -203,6 +206,10 @@ final class CodeWriter {
     emit(">");
   }
 
+  public void popTypeVariables(List<TypeVariableName> typeVariables) throws IOException {
+    typeVariables.forEach(typeVariable -> currentTypeVariables.remove(typeVariable.name));
+  }
+
   public CodeWriter emit(String s) throws IOException {
     return emitAndIndent(s);
   }
@@ -353,6 +360,12 @@ final class CodeWriter {
    * names visible due to inheritance.
    */
   String lookupName(ClassName className) {
+    // If the top level simple name is masked by a current type variable, use the canonical name.
+    String topLevelSimpleName = className.topLevelClassName().simpleName();
+    if (currentTypeVariables.contains(topLevelSimpleName)) {
+      return className.canonicalName;
+    }
+
     // Find the shortest suffix of className that resolves to className. This uses both local type
     // names (so `Entry` in `Map` refers to `Map.Entry`). Also uses imports.
     boolean nameResolved = false;
@@ -374,7 +387,7 @@ final class CodeWriter {
 
     // If the class is in the same package, we're done.
     if (Objects.equals(packageName, className.packageName())) {
-      referencedNames.add(className.topLevelClassName().simpleName());
+      referencedNames.add(topLevelSimpleName);
       return join(".", className.simpleNames());
     }
 
@@ -494,4 +507,26 @@ final class CodeWriter {
     result.keySet().removeAll(referencedNames);
     return result;
   }
+
+  // A makeshift multi-set implementation
+  private static final class Multiset<T> {
+    private final Map<T, Integer> map = new LinkedHashMap<>();
+
+    void add(T t) {
+      int count = map.getOrDefault(t, 0);
+      map.put(t, count + 1);
+    }
+
+    void remove(T t) {
+      int count = map.getOrDefault(t, 0);
+      if (count == 0) {
+        throw new IllegalStateException(t + " is not in the multiset");
+      }
+      map.put(t, count - 1);
+    }
+
+    boolean contains(T t) {
+      return map.getOrDefault(t, 0) > 0;
+    }
+  }
 }
diff --git a/src/main/java/com/squareup/javapoet/MethodSpec.java b/src/main/java/com/squareup/javapoet/MethodSpec.java
index a2c7c43..52b41e7 100644
--- a/src/main/java/com/squareup/javapoet/MethodSpec.java
+++ b/src/main/java/com/squareup/javapoet/MethodSpec.java
@@ -137,6 +137,7 @@ public final class MethodSpec {
 
       codeWriter.emit("}\n");
     }
+    codeWriter.popTypeVariables(typeVariables);
   }
 
   public boolean hasModifier(Modifier modifier) {
diff --git a/src/main/java/com/squareup/javapoet/TypeSpec.java b/src/main/java/com/squareup/javapoet/TypeSpec.java
index 46de3a5..c315579 100644
--- a/src/main/java/com/squareup/javapoet/TypeSpec.java
+++ b/src/main/java/com/squareup/javapoet/TypeSpec.java
@@ -316,6 +316,7 @@ public final class TypeSpec {
 
       codeWriter.unindent();
       codeWriter.popType();
+      codeWriter.popTypeVariables(typeVariables);
 
       codeWriter.emit("}");
       if (enumName == null && anonymousTypeArguments == null) {