Commit ffde2348 authored by Committed by Marge BotBrowse files
Do eager instantation in terms
This patch implements eager instantiation, a small but critical change to the type inference engine, #17173. The main change is this: When inferring types, always return an instantiated type (for now, deeply instantiated; in future shallowly instantiated) There is more discussion in https://www.tweag.io/posts/2020-04-02-lazy-eager-instantiation.html There is quite a bit of refactoring in this patch: * The ir_inst field of GHC.Tc.Utils.TcType.InferResultk has entirely gone. So tcInferInst and tcInferNoInst have collapsed into tcInfer. * Type inference of applications, via tcInferApp and tcInferAppHead, are substantially refactored, preparing the way for Quick Look impredicativity. * New pure function GHC.Tc.Gen.Expr.collectHsArgs and applyHsArgs are beatifully dual. We can see the zipper! * GHC.Tc.Gen.Expr.tcArgs is now much nicer; no longer needs to return a wrapper * In HsExpr, HsTypeApp now contains the the actual type argument, and is used in desugaring, rather than putting it in a mysterious wrapper. * I struggled a bit with good error reporting in Unify.matchActualFunTysPart. It's a little bit simpler than before, but still not great. Some smaller things * Rename tcPolyExpr --> tcCheckExpr tcMonoExpr --> tcLExpr * tcPatSig moves from GHC.Tc.Gen.HsType to GHC.Tc.Gen.Pat Metric Decrease: T9961 Reduction of 1.6% in comiler allocation on T9961, I think.