Experiment with eliminating the younger tyvar
authorSimon Peyton Jones <simonpj@microsoft.com>
Wed, 31 Jan 2018 15:58:12 +0000 (15:58 +0000)
committerSimon Peyton Jones <simonpj@microsoft.com>
Thu, 1 Feb 2018 10:56:28 +0000 (10:56 +0000)
commit618a805b0313ce256fa7b8293f851b32913bace5
treea79e125c5db6791225865b6bde1dbd7939b9e747
parentced9fbd3913e1316498961bc389bfb1e141221a1
Experiment with eliminating the younger tyvar

This patch is comments only, plus a minor refactor that
does not change behaviour.

It just records an idea I had for reducing kick-out in the type
constraint-solver.

See Note [Eliminate younger unification variables] in TcUnify.

Sadly, it didn't improve perf, so I've put it aside, leaving
some breadcrumbs for future generations of GHC hackers.
compiler/basicTypes/Unique.hs
compiler/typecheck/TcCanonical.hs
compiler/typecheck/TcUnify.hs