diff options
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 |