Missing cast in string interpolation

[ds5678]

Input code

public string ContainsCast(int i)
{
	return $"a_{(short)i}_b";
}

public string ContainsCast(long i)
{
	return $"a_{(int)i}_b";
}

Erroneous output

public string ContainsCast(int i)
{
	return $"a_{(short)i}_b";
}

public string ContainsCast(long i)
{
	return $"a_{i}_b";
}

The absence of the cast in the second method is a behavioral change, and the problem only exhibits on the "Roslyn Latest" unit tests.

Details

• Product in use: ILSpy unit testing
• Version in use: latest commit
• Any other relevant information to the issue, or your interest in contributing a fix.
  • I discovered this while working on Parenthesize interpolations containing global:: #3463

[ds5678]

I did some debugging, and I think the problem is caused by this branch.

ILSpy/ICSharpCode.Decompiler/CSharp/ExpressionBuilder.cs

Lines 2287 to 2291 in 03b7444

	// For non-small integer types, we can let the whole unchecked truncation
	// get handled by our caller (using the ExpressionBuilder post-condition).
	// Case 4 (left-over extension from implicit conversion) can also be handled by our caller.
	return arg.WithILInstruction(inst);