Support Range for non ValueTuple by remove the GetOffsetAndLength method

[wherewhere]

Description (optional)

Support Range for non ValueTuple by remove the GetOffsetAndLength method

Rationale

Code like "Hello World"[..5] does not need to use Range. It just be compiled to "Hello World".Substring(0, 5). So please remove GetOffsetAndLength when ValueTuple is not referenced like this Range.cs.

[wherewhere]

Things like (a, b) = (b, a) does not need to use ValueTuple. Why they have to check ValueTuple existing?

[hez2010]

Things like (a, b) = (b, a) does not need to use ValueTuple. Why they have to check ValueTuple existing?

The final codegen of swapping variables not using ValueTuple due to optimization doesn't mean the compiler won't check the existence of ValueTuple to make sure the ValueTuple feature itself works. And the compiler still needs to get the type ValueTuple so that it can bind the symbols, otherwise the type of (a, b) and (b, a) will be unknown at compile time.

[wherewhere]

But (a, b) = (b, a) can't be ValueTuple. Create ValueTuple need (var c, var d) = (b, a). Distrust (a, b) = c seems not check ValueTuple.

[hez2010]

You are trying to construct a ValueTuple at the right expression (b, a), but as for (a, b) = c where (a, b) is on the left, it is a completedly unrelated feature called destruction.

[wherewhere]

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