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author | Eric Seidel <gridaphobe@gmail.com> | 2015-12-23 10:10:04 +0100 |
---|---|---|
committer | Ben Gamari <ben@smart-cactus.org> | 2015-12-23 11:30:42 +0100 |
commit | 380b25ea4754c2aea683538ffdb179f8946219a0 (patch) | |
tree | 722784415e0f1b29a46fc115baff56f3495c0c9b /testsuite/tests/array | |
parent | 78248702b0b8189d73f08c89d86f5cb7a3c6ae8c (diff) | |
download | haskell-380b25ea4754c2aea683538ffdb179f8946219a0.tar.gz |
Allow CallStacks to be frozen
This introduces "freezing," an operation which prevents further
locations from being appended to a CallStack. Library authors may want
to prevent CallStacks from exposing implementation details, as a matter
of hygiene. For example, in
```
head [] = error "head: empty list"
ghci> head []
*** Exception: head: empty list
CallStack (from implicit params):
error, called at ...
```
including the call-site of `error` in `head` is not strictly necessary
as the error message already specifies clearly where the error came
from.
So we add a function `freezeCallStack` that wraps an existing CallStack,
preventing further call-sites from being pushed onto it. In other words,
```
pushCallStack callSite (freezeCallStack callStack) = freezeCallStack callStack
```
Now we can define `head` to not produce a CallStack at all
```
head [] =
let ?callStack = freezeCallStack emptyCallStack
in error "head: empty list"
ghci> head []
*** Exception: head: empty list
CallStack (from implicit params):
error, called at ...
```
---
1. We add the `freezeCallStack` and `emptyCallStack` and update the
definition of `CallStack` to support this functionality.
2. We add `errorWithoutStackTrace`, a variant of `error` that does not
produce a stack trace, using this feature. I think this is a sensible
wrapper function to provide in case users want it.
3. We replace uses of `error` in base with `errorWithoutStackTrace`. The
rationale is that base does not export any functions that use CallStacks
(except for `error` and `undefined`) so there's no way for the stack
traces (from Implicit CallStacks) to include user-defined functions.
They'll only contain the call to `error` itself. As base already has a
good habit of providing useful error messages that name the triggering
function, the stack trace really just adds noise to the error. (I don't
have a strong opinion on whether we should include this third commit,
but the change was very mechanical so I thought I'd include it anyway in
case there's interest)
4. Updates tests in `array` and `stm` submodules
Test Plan: ./validate, new test is T11049
Reviewers: simonpj, nomeata, goldfire, austin, hvr, bgamari
Reviewed By: simonpj
Subscribers: thomie
Projects: #ghc
Differential Revision: https://phabricator.haskell.org/D1628
GHC Trac Issues: #11049
Diffstat (limited to 'testsuite/tests/array')
-rw-r--r-- | testsuite/tests/array/should_run/arr003.stderr | 2 | ||||
-rw-r--r-- | testsuite/tests/array/should_run/arr004.stderr | 2 | ||||
-rw-r--r-- | testsuite/tests/array/should_run/arr007.stderr | 2 | ||||
-rw-r--r-- | testsuite/tests/array/should_run/arr008.stderr | 2 |
4 files changed, 0 insertions, 8 deletions
diff --git a/testsuite/tests/array/should_run/arr003.stderr b/testsuite/tests/array/should_run/arr003.stderr index a0d56ed0a6..8f3945286b 100644 --- a/testsuite/tests/array/should_run/arr003.stderr +++ b/testsuite/tests/array/should_run/arr003.stderr @@ -1,3 +1 @@ arr003: Ix{Int}.index: Index (4) out of range ((1,3)) -CallStack (from ImplicitParams): - error, called at libraries/base/GHC/Arr.hs:176:5 in base:GHC.Arr diff --git a/testsuite/tests/array/should_run/arr004.stderr b/testsuite/tests/array/should_run/arr004.stderr index e109855a71..b69cbf5b62 100644 --- a/testsuite/tests/array/should_run/arr004.stderr +++ b/testsuite/tests/array/should_run/arr004.stderr @@ -1,3 +1 @@ arr004: (Array.!): undefined array element -CallStack (from ImplicitParams): - error, called at libraries/base/GHC/Arr.hs:402:16 in base:GHC.Arr diff --git a/testsuite/tests/array/should_run/arr007.stderr b/testsuite/tests/array/should_run/arr007.stderr index 4c02cecf6e..feaa5d8363 100644 --- a/testsuite/tests/array/should_run/arr007.stderr +++ b/testsuite/tests/array/should_run/arr007.stderr @@ -1,3 +1 @@ arr007: Ix{Int}.index: Index (1) out of range ((1,0)) -CallStack (from ImplicitParams): - error, called at libraries/base/GHC/Arr.hs:176:5 in base:GHC.Arr diff --git a/testsuite/tests/array/should_run/arr008.stderr b/testsuite/tests/array/should_run/arr008.stderr index 5355a07162..f926f7288c 100644 --- a/testsuite/tests/array/should_run/arr008.stderr +++ b/testsuite/tests/array/should_run/arr008.stderr @@ -1,3 +1 @@ arr008: Ix{Int}.index: Index (2) out of range ((0,1)) -CallStack (from ImplicitParams): - error, called at libraries/base/GHC/Arr.hs:176:5 in base:GHC.Arr |