with expression containing an await leaves the raw <Clone>$ call in the output

[christophwille]

A with expression whose initializer contains an await is not recognized: the compiler-generated <Clone>$ call survives into the output under its escaped name.

Input

public record Record(int X);

private static Task<int> Get()
{
	return Task.FromResult(1);
}

public async Task<Record> WithExpressionContainingAwait(Record value)
{
	return value with {
		X = await Get()
	};
}

Actual output

public async Task<Record> WithExpressionContainingAwait(Record value)
{
	Record record = value._003CClone_003E_0024();
	Record record2 = record;
	record2.X = await Get();
	return record;
}

_003CClone_003E_0024 is the escaped <Clone>$; the output does not compile.

Expected output

public async Task<Record> WithExpressionContainingAwait(Record value)
{
	return value with {
		X = await Get()
	};
}

Notes

The await is what defeats it - the same with expression round-trips when the initializer has no suspension point. The state-machine split puts the clone call and the property assignment in different blocks, so the transform that recognizes the with-expression pattern no longer sees them adjacent.

[dgrunwald]

This likely has the same root cause as #4018.