• Eric Seidel's avatar
    Use IP based CallStack in error and undefined · 6740d70d
    Eric Seidel authored
    This patch modifies `error`, `undefined`, and `assertError` to use
    implicit call-stacks to provide better error messages to users.
    There are a few knock-on effects:
    - `GHC.Classes.IP` is now wired-in so it can be used in the wired-in
      types for `error` and `undefined`.
    - `TysPrim.tyVarList` has been replaced with a new function
      `TysPrim.mkTemplateTyVars`. `tyVarList` made it easy to introduce
      subtle bugs when you need tyvars of different kinds. The naive
      tv1 = head $ tyVarList kind1
      tv2 = head $ tyVarList kind2
      would result in `tv1` and `tv2` sharing a `Unique`, thus substitutions
      would be applied incorrectly, treating `tv1` and `tv2` as the same
      tyvar. `mkTemplateTyVars` avoids this pitfall by taking a list of kinds
      and producing a single tyvar of each kind.
    - The types `GHC.SrcLoc.SrcLoc` and `GHC.Stack.CallStack` now live in
    - The type `GHC.Exception.ErrorCall` has a new constructor
      `ErrorCallWithLocation` that takes two `String`s instead of one, the
      2nd one being arbitrary metadata about the error (but usually the
      call-stack). A bi-directional pattern synonym `ErrorCall` continues to
      provide the old API.
    Updates Cabal, array, and haddock submodules.
    Reviewers: nh2, goldfire, simonpj, hvr, rwbarton, austin, bgamari
    Reviewed By: simonpj
    Subscribers: rwbarton, rodlogic, goldfire, maoe, simonmar, carter,
    liyang, bgamari, thomie
    Differential Revision: https://phabricator.haskell.org/D861
    GHC Trac Issues: #5273
TcInteract.hs 75.4 KB