Motivation

numberToRangedRational: fix edge cases for exp ≈ (maxBound :: Int)

Currently a negative exponent less than minBound :: Int results in
Infinity, which is very surprising and obviously wrong.

λ> read "1e-9223372036854775808" :: Double                          
0.0                                                                 
λ> read "1e-9223372036854775809" :: Double                          
Infinity                                                            

There is a further edge case where the exponent can overflow when
increased by the number of tens places in the integer part, or
underflow when decreased by the number of leading zeros in the
fractional part if the integer part is zero:

λ> read "10e9223372036854775807" :: Double                          
0.0                                                                 
λ> read "0.01e-9223372036854775808" :: Double                       
Infinity                                                            

Proposal

Fix these bugs. The exponent should not wrap and return Infinity (in case of underflow) or 0 (in case of overflow).
There is a merge request.

Impact

This improves the accuracy of floating point parsing on some extreme cases. Most ordinary programs or use cases are not likely to be affected. Users that are affected would presumably be pleased with this change.