BigInt parsing allows whitespace

[Liozou]

julia> parse(Int, "100 10")
ERROR: ArgumentError: extra characters after whitespace in "100 10"

julia> parse(BigInt, "100 10")
10010

The second case is the oddity here, and it seems to originate from

julia/base/gmp.jl

Line 284 in f5d1557

err = GC.@preserve bstr MPZ.set_str!(z, pointer(bstr)+(i-firstindex(bstr)), base)

aka MPZ.set_str! does not follow Julia conventions for parsing numbers.

Originally posted by @Liozou in #44550 (comment)

Copy-pasted from #44550, discovered by @henriquebecker91

[PallHaraldsson]

I'm not sure how (easy it is) to fix this.

I like better to just drop BigInt support... move it too a package (making Julia smaller), yes a breaking change, or could still be loaded by default, conditional on an ENV var.

Not having it (be default or not) would get rid of a number of bugs like this one, and e.g. #52862

[quinnj]

Note that Parsers.jl correctly errors in this case (though admittedly the error message mentioning "SUCCESS" is probably confusing along with the absence of a helpful error message):

julia> Parsers.parse(BigInt, "100 10")
ERROR: Parsers.Error (SUCCESS: OK ):
initial value parsing succeeded
attempted to parse BigInt from: "100 10"

Stacktrace:
 [1] parse
   @ ~/.julia/dev/Parsers/src/Parsers.jl:366 [inlined]
 [2] parse(::Type{BigInt}, buf::String)
   @ Parsers ~/.julia/dev/Parsers/src/Parsers.jl:362
 [3] top-level scope
   @ REPL[7]:1