-
fe6ed8d9
by Sylvain Henry at 2025-04-24T18:04:12-04:00
Doc: add doc for JS interruptible calling convention (#24444)
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6111c5e4
by Ben Gamari at 2025-04-24T18:04:53-04:00
compiler: Ensure that Panic.Plain.assertPanic' provides callstack
In 36cddd2ce1a3bc62ea8a1307d8bc6006d54109cf @alt-romes removed CallStack
output from `GHC.Utils.Panic.Plain.assertPanic'`. While this output is
redundant due to the exception backtrace proposal, we may be
bootstrapping with a compiler which does not yet include this machinery.
Reintroduce the output for now.
Fixes #25898.
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217caad1
by Matthew Pickering at 2025-04-25T18:58:42+01:00
Implement Explicit Level Imports for Template Haskell
This commit introduces the `ExplicitLevelImports` and
`ImplicitStagePersistence` language extensions as proposed in GHC
Proposal #682.
Key Features
------------
- `ExplicitLevelImports` adds two new import modifiers - `splice` and
`quote` - allowing precise control over the level at which imported
identifiers are available
- `ImplicitStagePersistence` (enabled by default) preserves existing
path-based cross-stage persistence behavior
- `NoImplicitStagePersistence` disables implicit cross-stage
persistence, requiring explicit level imports
Benefits
--------
- Improved compilation performance by reducing unnecessary code generation
- Enhanced IDE experience with faster feedback in `-fno-code` mode
- Better dependency tracking by distinguishing compile-time and runtime dependencies
- Foundation for future cross-compilation improvements
This implementation enables the separation of modules needed at
compile-time from those needed at runtime, allowing for more efficient
compilation pipelines and clearer code organization in projects using
Template Haskell.
Implementation Notes
--------------------
The level which a name is availble at is stored in the 'GRE', in the normal
GlobalRdrEnv. The function `greLevels` returns the levels which a specific GRE
is imported at. The level information for a 'Name' is computed by `getCurrentAndBindLevel`.
The level validity is checked by `checkCrossLevelLifting`.
Instances are checked by `checkWellLevelledDFun`, which computes the level an
instance by calling `checkWellLevelledInstanceWhat`, which sees what is
available at by looking at the module graph.
Modifications to downsweep
--------------------------
Code generation is now only enabled for modules which are needed at
compile time.
See the Note [-fno-code mode] for more information.
Uniform error messages for level errors
---------------------------------------
All error messages to do with levels are now reported uniformly using
the `TcRnBadlyStaged` constructor.
Error messages are uniformly reported in terms of levels.
0 - top-level
1 - quote level
-1 - splice level
The only level hard-coded into the compiler is the top-level in
GHC.Types.ThLevelIndex.topLevelIndex.
Uniformly refer to levels and stages
------------------------------------
There was much confusion about levels vs stages in the compiler.
A level is a semantic concept, used by the typechecker to ensure a
program can be evaluated in a well-staged manner.
A stage is an operational construct, program evaluation proceeds in
stages.
Deprecate -Wbadly-staged-types
------------------------------
`-Wbadly-staged-types` is deprecated in favour of `-Wbadly-levelled-types`.
Lift derivation changed
-----------------------
Derived lift instances will now not generate code with expression
quotations.
Before:
```
data A = A Int deriving Lift
=>
lift (A x) = [| A $(lift x) |]
```
After:
```
lift (A x) = conE 'A `appE` (lift x)
```
This is because if you attempt to derive `Lift` in a module where
`NoImplicitStagePersistence` is enabled, you would get an infinite loop
where a constructor was attempted to be persisted using the instance you
are currently defining.
GHC API Changes
---------------
The ModuleGraph now contains additional information about the type of
the edges (normal, quote or splice) between modules. This is abstracted
using the `ModuleGraphEdge` data type.
Fixes #25828
-------------------------
Metric Increase:
MultiLayerModulesTH_Make
-------------------------
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7641a74a
by Simon Peyton Jones at 2025-04-26T22:05:19-04:00
Get a decent MatchContext for pattern synonym bindings
In particular when we have a pattern binding
K p1 .. pn = rhs
where K is a pattern synonym. (It might be nested.)
This small MR fixes #25995. It's a tiny fix, to an error message,
removing an always-dubious `unkSkol`.
The bug report was in the context of horde-ad, a big program,
and I didn't manage to make a small repro case quickly. I decided
not to bother further.
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ce616f49
by Simon Peyton Jones at 2025-04-27T21:10:25+01:00
Fix infelicities in the Specialiser
On the way to #23109 (unary classes) I discovered some infelicities
(or maybe tiny bugs, I forget) in the type-class specialiser.
I also tripped over #25965, an outright bug in the rule matcher
Specifically:
* Refactor: I enhanced `wantCallsFor`, whih previously always said
`True`, to discard calls of class-ops, data constructors etc. This is
a bit more efficient; and it means we don't need to worry about
filtering them out later.
* Fix: I tidied up some tricky logic that eliminated redundant
specialisations. It wasn't working correctly. See the expanded
Note [Specialisations already covered], and
(MP3) in Note [Specialising polymorphic dictionaries].
See also the new top-level `alreadyCovered`
function, which now goes via `GHC.Core.Rules.ruleLhsIsMoreSpecific`
I also added a useful Note [The (CI-KEY) invariant]
* Fix #25965: fixed a tricky bug in the `go_fam_fam` in
`GHC.Core.Unify.uVarOrFam`, which allows matching to succeed
without binding all type varibles.
I enhanced Note [Apartness and type families] some more
* #25703. This ticket "just works" with -fpolymorphic-specialisation;
but I was surprised that it worked! In this MR I added documentation
to Note [Interesting dictionary arguments] to explain; and tests to
ensure it stays fixed.
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22d11fa8
by Simon Peyton Jones at 2025-04-28T18:05:19-04:00
Track rewriter sets more accurately in constraint solving
The key change, which fixed #25440, is to call `recordRewriter` in
GHC.Tc.Solver.Rewrite.rewrite_exact_fam_app. This missing call meant
that we were secretly rewriting a Wanted with a Wanted, but not really
noticing; and that led to a very bad error message, as you can see
in the ticket.
But of course that led me into rabbit hole of other refactoring around
the RewriteSet code:
* Improve Notes [Wanteds rewrite Wanteds]
* Zonk the RewriterSet in `zonkCtEvidence` rather than only in GHC.Tc.Errors.
This is tidier anyway (e.g. de-clutters debug output), and helps with the
next point.
* In GHC.Tc.Solver.Equality.inertsCanDischarge, don't replace a constraint
with no rewriters with an equal constraint that has many. See
See (CE4) in Note [Combining equalities]
* Move zonkRewriterSet and friends from GHC.Tc.Zonk.Type into
GHC.Tc.Zonk.TcType, where they properly belong.
A handful of tests get better error messages.
For some reason T24984 gets 12% less compiler allocation -- good
Metric Decrease:
T24984
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1fb071db
by Andreas Klebinger at 2025-04-29T10:17:02+01:00
Try to relax specialization requirements we put on args.
Dont make comment seem like haddock
Test things
Wibble
Try simons version of isInterestingDict
Disable trace for ci checks
use inscope set
Add test cases
Polishing up from Simon
Rmoved accidentally committed traces
and add missing import
Typos
Remove a special case that appears to do nothing
See the commented-out block of `specCase`
Wibbles
Another subtle wibble: (ID8)