Adjust asserts in OverloadResolutionResult.ReportDiagnostics. (#55899)

Fixes #52701.

src/Compilers/CSharp/Portable/Binder/Semantics/OverloadResolution/OverloadResolutionResult.cs

@@ -251,12 +251,6 @@ internal void ReportDiagnostics<T>(
  // there also can't be a single one. Therefore, there are none.
  AssertNone(MemberResolutionKind.Worse);
 
- // If there's a less-derived candidate, it must be less derived than some applicable or
- // "worse" candidate. Since there are none of those, there must not be any less-derived
- // candidates either.
- AssertNone(MemberResolutionKind.LessDerived);
-
-
  //// PHASE 2: Applicability failures ////
 
  // Overload resolution performed these checks just before weeding out less-derived and worse candidates.
@@ -305,6 +299,11 @@ internal void ReportDiagnostics<T>(
  // Since we didn't return...
  AssertNone(MemberResolutionKind.ConstraintFailure);
 
+ // If there's a less-derived candidate, it must be less derived than some applicable or
+ // "worse" candidate. Since there are none of those, there must not be any less-derived
+ // candidates either.
+ AssertNone(MemberResolutionKind.LessDerived);
+
  // Otherwise, if there is any such method that has a bad argument conversion or out/ref mismatch
  // then the first such method found is the best bad method.
 

src/Compilers/CSharp/Test/Semantic/Semantics/OverloadResolutionTests.cs

@@ -11411,5 +11411,61 @@ static void verify(CSharpCompilation comp, SyntaxTree tree)
  Assert.Equal("event D<A, B> Base<A, B>.E", symbol.ToTestDisplayString());
  }
  }
+
+ [Fact]
+ [WorkItem(52701, "https://github.com/dotnet/roslyn/issues/52701")]
+ public void Issue52701_01()
+ {
+ var source =
+@"
+class A
+{
+ internal void F<T>(T t) where T : class {}
+}
+class B : A
+{
+ internal new void F<T>(T t) where T : struct { }
+ void M()
+ {
+ System.Action<object> d = F<object>;
+ }
+}
+";
+
+ var comp = CreateCompilation(source);
+ comp.VerifyDiagnostics(
+ // (11,35): error CS0453: The type 'object' must be a non-nullable value type in order to use it as parameter 'T' in the generic type or method 'B.F<T>(T)'
+ // System.Action<object> d = F<object>;
+ Diagnostic(ErrorCode.ERR_ValConstraintNotSatisfied, "F<object>").WithArguments("B.F<T>(T)", "T", "object").WithLocation(11, 35)
+ );
+ }
+
+ [Fact]
+ [WorkItem(52701, "https://github.com/dotnet/roslyn/issues/52701")]
+ public void Issue52701_02()
+ {
+ var source =
+@"
+class A
+{
+ internal void F<T>(T t) where T : class {}
+}
+class B : A
+{
+ internal new void F<T>(T t) where T : struct { }
+ void M()
+ {
+ F<object>(default);
+ }
+}
+";
+
+ var comp = CreateCompilation(source);
+ comp.VerifyDiagnostics(
+ // (11,9): error CS0453: The type 'object' must be a non-nullable value type in order to use it as parameter 'T' in the generic type or method 'B.F<T>(T)'
+ // F<object>(default);
+ Diagnostic(ErrorCode.ERR_ValConstraintNotSatisfied, "F<object>").WithArguments("B.F<T>(T)", "T", "object").WithLocation(11, 9)
+ );
+ }
  }
 }