[BUG] Unify the constructor signature for pointer-based initialization across multiple types

[soraros]

That said, the unsafe constructors from pointers are really a mess, and I find myself having to look up the keyword names every time. Could we adopt a convention like fn __init__(inout self, *, ptr: UnsafePointer, len: Int)?

• String: fn __init__(inout self, ptr: UnsafePointer[UInt8], len: Int):
• StringRef: fn __init__(inout self, ptr: UnsafePointer[c_char], len: Int):
• StringSlice: fn __init__(inout self, *, unsafe_from_utf8_ptr: UnsafePointer[UInt8], len: Int):
• Span: fn __init__(inout self, *, unsafe_ptr: UnsafePointer[T], len: Int):
• List: fn __init__(inout self, *, unsafe_pointer: UnsafePointer[T], size: Int, capacity: Int):

Agreed, they're wildly inconsistent. +1 to your proposed convention - feel free to open a PR. I'm also +1 for making them all (including String kw-only for the ptr + len constructor until we fix implicit constructor issue you linked).

Originally posted by @JoeLoser in #3698 (comment)

[martinvuyk]

I agree that it's necessary, but I'll be a bit nit-picky and very subjective: since we are defining a new standard, I wanted to say that I strongly dislike using len as argument since it is the name of a builtin function. I personally prefer going for length.

[JoeLoser]

I agree that it's necessary, but I'll be a bit nit-picky and very subjective: since we are defining a new standard, I wanted to say that I strongly dislike using len as argument since it is the name of a builtin function. I personally prefer going for length.

Agreed given that argument. I'd be fine with length.