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| author | sheaf <sam.derbyshire@gmail.com> | 2022-05-11 13:17:41 +0200 |
|---|---|---|
| committer | Marge Bot <ben+marge-bot@smart-cactus.org> | 2022-05-12 18:14:34 -0400 |
| commit | 3bf938b6c5e1190f3a55e149deaec2f6309d398f (patch) | |
| tree | c3bde01d0456a05f956222bf06b3de8816be803c /docs | |
| parent | b8c5ffab70fbd4e9b01a180359800188191cca47 (diff) | |
| download | haskell-3bf938b6c5e1190f3a55e149deaec2f6309d398f.tar.gz | |
Update extending_ghc for TcPlugin changes
The documentation still mentioned Derived constraints and
an outdated datatype TcPluginResult.
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/users_guide/extending_ghc.rst | 12 |
1 files changed, 6 insertions, 6 deletions
diff --git a/docs/users_guide/extending_ghc.rst b/docs/users_guide/extending_ghc.rst index c12abc2b4c..1cec248364 100644 --- a/docs/users_guide/extending_ghc.rst +++ b/docs/users_guide/extending_ghc.rst @@ -652,8 +652,8 @@ The key component of a typechecker plugin is a function of type :: - solve :: [Ct] -> [Ct] -> [Ct] -> TcPluginM TcPluginResult - solve givens deriveds wanteds = ... + solve :: [Ct] -> [Ct] -> TcPluginM TcPluginSolveResult + solve givens wanteds = ... This function will be invoked in two different ways: @@ -676,11 +676,11 @@ The plugin can then respond with: The plugin must respond with constraints of the same flavour, i.e. in (1) it should return only Givens, and for (2) it should return only -Wanteds (or Deriveds); all other constraints will be ignored. +Wanteds; all other constraints will be ignored. If the plugin cannot make any progress, it should return -``TcPluginSolveResult [] [] []``. Otherwise, if there were any new constraints, the -main constraint solver will be re-invoked to simplify them, then the +``TcPluginSolveResult [] [] []``. Otherwise, if there were any new constraints, +the main constraint solver will be re-invoked to simplify them, then the plugin will be invoked again. The plugin is responsible for making sure that this process eventually terminates. @@ -692,7 +692,7 @@ by solving or contradicting them). Constraints that have been solved by the plugin must be provided with evidence in the form of an ``EvTerm`` of the type of the constraint. -This evidence is ignored for Given and Derived constraints, which GHC +This evidence is ignored for Given constraints, which GHC "solves" simply by discarding them; typically this is used when they are uninformative (e.g. reflexive equations). For Wanted constraints, the evidence will form part of the Core term that is generated after |