Simplify some bits

Author: Garciat

src/main/java/com/garciat/typeclasses/processor/StaticWitnessSystem.java

@@ -15,18 +15,13 @@
 import javax.lang.model.element.TypeElement;
 import javax.lang.model.element.VariableElement;
 import javax.lang.model.type.*;
-import javax.lang.model.util.Types;
 
 public class StaticWitnessSystem {
   private static final Class<?> TAG_BASE_CLASS = TagBase.class;
   private static final Class<?> TAPP_CLASS = TApp.class;
   private static final Class<?> TPAR_CLASS = TPar.class;
 
-  private final Types types;
-
-  public StaticWitnessSystem(Types types) {
-    this.types = types;
-  }
+  public StaticWitnessSystem() {}
 
   public List<WitnessConstructor> findRules(ParsedType target) {
     return switch (target) {
@@ -42,7 +37,7 @@ public List<WitnessConstructor> findRules(ParsedType target) {
     };
   }
 
-  public Maybe<WitnessConstructor> parseWitnessConstructor(ExecutableElement method) {
+  private Maybe<WitnessConstructor> parseWitnessConstructor(ExecutableElement method) {
     if (method.getModifiers().contains(Modifier.PUBLIC)
         && method.getModifiers().contains(Modifier.STATIC)
         && method.getAnnotation(TypeClass.Witness.class) instanceof TypeClass.Witness witnessAnn) {
@@ -61,10 +56,6 @@ public Maybe<WitnessConstructor> parseWitnessConstructor(ExecutableElement metho
     }
   }
 
-  public List<ParsedType> parseAll(List<? extends TypeMirror> types) {
-    return types.stream().map(this::parse).toList();
-  }
-
   public ParsedType parse(TypeMirror type) {
     return switch (type) {
       case TypeVariable tv -> new ParsedType.Var(tv);
@@ -82,8 +73,9 @@ when parseAppType(dt)
                   Pair<TypeMirror, TypeMirror>(var fun, var arg)) ->
           new ParsedType.App(parse(fun), parse(arg));
       case DeclaredType dt ->
-          parseAll(dt.getTypeArguments()).stream()
-              .reduce(parse(types.erasure(dt)), ParsedType.App::new);
+          dt.getTypeArguments().stream()
+              .map(this::parse)
+              .reduce(new ParsedType.Const(erasure(dt)), ParsedType.App::new);
       case WildcardType wt ->
           throw new IllegalArgumentException("Cannot parse wildcard type: " + wt);
       default -> throw new IllegalArgumentException("Unsupported type: " + type);
@@ -104,7 +96,7 @@ private static Maybe<DeclaredType> parseTagType(DeclaredType t) {
   }
 
   private Maybe<Pair<TypeMirror, TypeMirror>> parseAppType(DeclaredType t) {
-    return t.getTypeArguments().size() == 2 && isAppType(types.erasure(t))
+    return t.getTypeArguments().size() == 2 && isAppType(erasure(t))
         ? Maybe.just(new Pair<>(t.getTypeArguments().get(0), t.getTypeArguments().get(1)))
         : Maybe.nothing();
   }
@@ -116,6 +108,10 @@ private boolean isAppType(TypeMirror erasure) {
             || te.getQualifiedName().contentEquals(TPAR_CLASS.getName()));
   }
 
+  private DeclaredType erasure(DeclaredType t) {
+    return t.asElement().asType() instanceof DeclaredType typeCtor ? typeCtor : t;
+  }
+
   private static <T extends U, U> Function<U, Stream<T>> isInstanceOf(Class<T> cls) {
     return u -> cls.isInstance(u) ? Stream.of(cls.cast(u)) : Stream.empty();
   }

src/main/java/com/garciat/typeclasses/processor/WitnessResolutionChecker.java

@@ -12,7 +12,6 @@
 import javax.lang.model.element.TypeElement;
 import javax.lang.model.type.DeclaredType;
 import javax.lang.model.type.TypeMirror;
-import javax.lang.model.util.Types;
 import javax.tools.Diagnostic;
 
 public final class WitnessResolutionChecker implements Plugin {
@@ -45,29 +44,23 @@ public void finished(TaskEvent e) {
               return;
             }
 
-            Trees trees = Trees.instance(task);
-            new WitnessCallScanner(trees, task.getTypes()).scan(e.getCompilationUnit(), trees);
+            new WitnessCallScanner(Trees.instance(task)).scan(e.getCompilationUnit(), null);
           }
         });
   }
 
   /** Scanner that finds calls to TypeClasses.witness() and validates them. */
-  private static class WitnessCallScanner extends TreePathScanner<Void, Trees> {
+  private static class WitnessCallScanner extends TreePathScanner<Void, Void> {
     private final Trees trees;
     private final StaticWitnessSystem system;
 
-    WitnessCallScanner(Trees trees, Types types) {
+    private WitnessCallScanner(Trees trees) {
       this.trees = trees;
-      this.system = new StaticWitnessSystem(types);
+      this.system = new StaticWitnessSystem();
     }
 
     @Override
-    public Void visitClass(ClassTree node, Trees trees) {
-      return super.visitClass(node, trees);
-    }
-
-    @Override
-    public Void visitMethodInvocation(MethodInvocationTree node, Trees trees) {
+    public Void visitMethodInvocation(MethodInvocationTree node, Void arg) {
       Element element = trees.getElement(getCurrentPath());
 
       if (isMethodCall(WITNESS_METHOD, element)) {
@@ -95,7 +88,7 @@ public Void visitMethodInvocation(MethodInvocationTree node, Trees trees) {
                   this.trees.printMessage(
                       Diagnostic.Kind.ERROR,
                       "Failed to resolve witness for type: "
-                          + target.format()
+                          + witnessTypeMirror
                           + "\nReason: "
                           + error.format(),
                       getCurrentPath().getLeaf(),
@@ -108,7 +101,7 @@ public Void visitMethodInvocation(MethodInvocationTree node, Trees trees) {
         }
       }
 
-      return super.visitMethodInvocation(node, trees);
+      return super.visitMethodInvocation(node, arg);
     }
   }