Prevent unions with itself (#1997)

* Remove stale reference * Don't suppress LHS diagnostics on augmented assign * Revert "Don't suppress LHS diagnostics on augmented assign" This reverts commit 6109ac7. * Escape [ and ] * PR feedback * Prevent unions with itself * Add special Union comparison + test

Author: Mikhail Arkhipov

src/Analysis/Ast/Impl/Types/PythonUnionType.cs

@@ -28,15 +28,19 @@ internal sealed class PythonUnionType : LocatedMember, IPythonUnionType {
 
  public PythonUnionType(IEnumerable<IPythonType> types, IPythonModule declaringModule)
  : base(declaringModule.Interpreter.ModuleResolution.GetSpecializedModule("typing")) {
- _types.UnionWith(types);
+ _types.UnionWith(types.Where(t => !this.Equals(t)));
  }
 
  private PythonUnionType(IPythonType x, IPythonType y)
  : base(x.DeclaringModule.Interpreter.ModuleResolution.GetSpecializedModule("typing")) {
  Check.Argument(nameof(x), () => !(x is IPythonUnionType));
  Check.Argument(nameof(y), () => !(y is IPythonUnionType));
- _types.Add(x);
- _types.Add(y);
+ if (!this.Equals(x)) {
+ _types.Add(x);
+ }
+ if (!this.Equals(y)) {
+ _types.Add(y);
+ }
  }
 
  public override PythonMemberType MemberType => PythonMemberType.Union;
@@ -91,7 +95,7 @@ public IMember Index(IPythonInstance instance, IArgumentSet args) {
  // Check if any types support indexing
  var result = types
  .Select(t => t.Index(instance, args))
- .FirstOrDefault(r => !r.IsUnknown() && r.GetPythonType() != this);
+ .FirstOrDefault(r => !r.IsUnknown() && !r.GetPythonType().Equals(this));
  return result ?? DeclaringModule.Interpreter.UnknownType;
  }
 
@@ -112,7 +116,7 @@ public IPythonUnionType Add(IPythonType t) {
 
  public IPythonUnionType Add(IPythonUnionType types) {
  lock (_lock) {
- _types.UnionWith(types);
+ _types.UnionWith(types.Where(t => !this.Equals(t)));
  return this;
  }
  }
@@ -158,5 +162,16 @@ public static IPythonType Combine(IPythonType x, IPythonType y) {
 
  return utx == null ? uty.Add(x) : utx.Add(uty);
  }
+
+ public override bool Equals(object obj) {
+ if (obj is PythonUnionType u) {
+ lock (_lock) {
+ return _types.SetEquals(u._types);
+ }
+ }
+ return false;
+ }
+
+ public override int GetHashCode() => 0;
  }
 }

src/Analysis/Ast/Test/TypingTests.cs

@@ -386,6 +386,34 @@ public void AnnotationParsing() {
  AssertTransform("Dict['Int, Str']", "NameOp:Dict", "StartListOp", "NameOp:Int", "NameOp:Str", "MakeGenericOp");
  }
 
+ [TestMethod, Priority(0)]
+ public async Task UnionsCompare() {
+ var analysis = await GetAnalysisAsync("from typing import Union", PythonVersions.LatestAvailable3X);
+ var i = analysis.Document.Interpreter.GetBuiltinType(BuiltinTypeId.Int);
+ var b = analysis.Document.Interpreter.GetBuiltinType(BuiltinTypeId.Bool);
+
+ var expected = new[] {i, b};
+ var u1 = new PythonUnionType(expected, analysis.Document);
+ var u2 = new PythonUnionType(expected, analysis.Document);
+
+ u2.Equals(u1).Should().BeTrue();
+ u1.Add(u2);
+ var actual = u1.ToArray();
+ actual.Should().Equal(expected);
+
+ u1.Add(u1);
+ actual = u1.ToArray();
+ actual.Should().Equal(expected);
+
+ u2.Add(u1);
+ actual = u2.ToArray();
+ actual.Should().Equal(expected);
+
+ u2.Add(u2);
+ actual = u1.ToArray();
+ actual.Should().Equal(expected);
+ }
+
  [TestMethod, Priority(0)]
  public void AnnotationConversion() {
  AssertConvert("List");