Exception in CSharpAddParameterCheckCodeRefactoringProvider when changing type of indexer argument

[jhinder]

Version Used: VS 17.3, Roslyn 4.3.0-3.22401.3

Steps to Reproduce:

1. Take the code below.
2. Select the type of the indexer argument and type any type name (valid or invalid).
3. A gold bar appears, stating "'CSharpAddParameterCheckCodeRefactoringProvider' encountered an error and has been disabled."

record R
{
    public int this[int i]
    {
        get => default;
    }
}

Stack trace:

System.InvalidCastException : Unable to cast object of type 'Microsoft.CodeAnalysis.CSharp.Symbols.PublicModel.PropertySymbol' to type 'Microsoft.CodeAnalysis.IMethodSymbol'.
   at async Microsoft.CodeAnalysis.InitializeParameter.AbstractInitializeParameterCodeRefactoringProvider`4.ComputeRefactoringsAsync[TTypeDeclarationSyntax,TParameterSyntax,TStatementSyntax,TExpressionSyntax](<Unknown Parameters>)
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at async Microsoft.CodeAnalysis.CodeRefactorings.CodeRefactoringService.GetRefactoringFromProviderAsync(<Unknown Parameters>)

Notes:

• Seems to affect only record types, not class or struct.
• An accessor must be explicitly defined (i.e. this[X x] => 0 is not affected), and it can be any of get, set or init.

Expected Behavior: No exception.

Actual Behavior: Exception and gold bar.