Error for using positional member that is hidden

[jcouv]

Fixes #52630

Relates to test plan: #51199
Spec change: dotnet/csharplang#4673

[Youssef1313]

Suggested change

	record Derived(int I) // error: The positional member `Base.I` found corresponding to parameter `I` is hidden.
	record Derived(int I) // error: The positional member 'Base.I' found corresponding to this parameter is hidden.
	``` #Resolved

[Youssef1313]

Could be moved outside the loop? #Resolved

[Youssef1313]

• When can the this condition be false?

• What if the Deconstruct method is declared explicitly:

  public record Base
  {
      public int I { get; set; } = 42;
      public Base(int ignored) { }
  
      public void Deconstruct(out string s, out string s2) { s = s2 = "";  }
  }
  public record C(int I) : Base(I)
  {
      public void I() { }
  
      public void Deconstruct(out string s, out string s2) { s = s2 = "";  }
  }
  ``` #Resolved

[jcouv]

• the condition is false when addProperties in SourceMemberContainerSymbol doesn't find a property for each parameter (we produce ERR_BadRecordMemberForPositionalParameter in that case).
• thanks. I need to think more about scenarios where Deconstruct is declared in source. We should produce a diagnostic too, but currently don't.

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In reply to: 614614357 [](ancestors = 614614357)

[Youssef1313]

If prop is abstract, it won't be validated, is that intended? i.e:

abstract record Base
{
    public abstract int I { get; init; }
}

record Derived(int I) : Base
{
    public int I() { return 0; }
}

#Resolved

[jcouv]

In that scenario Derived defined a concrete property I and a method I() (that's an error). The positional member is Derived.I so we didn't pick a hidden member, so the new error doesn't come into play.
Added tests to illustrate. Thanks for the scenario. #Resolved

[AlekseyTs]

Done with review pass (commit 9)

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In reply to: 822644422

[AlekseyTs]

LGTM (commit 11)