throw LightBoundsError instead of BoundsError

[nsajko]

Context: While BoundsError is common in the Julia world, its use is problematic for compiler optimizations. More specifically, Julia is gaining the ability to eliminate heap allocations as of recently, even for code that is not eliminated by dead code elimination or eliminated by constant folding. After the compiler gains interprocedural escape analysis capabilities, elimination of heap allocations should become applicable more often. The problem with BoundsError is that a BoundsError value holds a reference to the array that was attempted to be indexed out-of-bounds. Thus a BoundsError throw escapes the value of the array. Thus a BoundsError throw makes the elimination of the underlying heap allocation impossible, unless the throw is first eliminated by @inbounds or by other compiler optimizations.

The LightBoundsError exception from package LightBoundsErrors.jl addresses this by storing typeof(array) and axes(array) instead of storing array. The new package is already adopted as a dependency by FixedSizeArrays.jl.

Switching from BoundsError to LightBoundsError could hypothetically break a dependent of MemoryViews, in case a dependent branches on something like exception isa BoundsError while error handling.

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• I have updated any relevant documentation and docstrings.
• I have added unit tests, and the CodeCov bot shows tests cover my new code.
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[codecov]

Codecov Report

❌ Patch coverage is 76.92308% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 97.89%. Comparing base (ad50c1e) to head (bdbf158).
⚠️ Report is 7 commits behind head on master.

Files with missing lines	Patch %	Lines
src/basic.jl	72.72%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #37      +/-   ##
==========================================
+ Coverage   97.88%   97.89%   +0.01%     
==========================================
  Files          10       10              
  Lines         331      333       +2     
==========================================
+ Hits          324      326       +2     
  Misses          7        7              

Flag	Coverage Δ
unittests	97.89% <76.92%> (+0.01%)	⬆️

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[jakobnissen]

This is a good idea. Too bad that BoundsError was designed that way. I'm going to roll it up with #19 when releasing v0.4

[jakobnissen]

LGTM. Its still a draft, but whenever you set it ready to merge, I’ll review the package for whether any APIs could use an overhaul, then release v0.4