Move the Error trait into core (without `fn backtrace`)#90328

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yaahc wants to merge 5 commits intorust-lang:masterfrom yaahc:error-in-core

+1,467-9

Commits on Dec 21, 2021

Commits on Dec 22, 2021

implement source in terms of generic member access
yaahc
committed

Commits on Apr 5, 2022

Add ui tests for checking instability
yaahc
committed