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Alan Zimmerman pushed to branch wip/az/ghc-cpp at Glasgow Haskell Compiler / GHC

Commits:

e0f3ff11

by Patrick at 2025-04-17T04:31:12-04:00

Refactor Handling of Multiple Default Declarations

Fixes: #25912, #25914, #25934

Previously, GHC discarded all loaded defaults (tcg_default) when local
defaults were encountered during typechecking. According to the
exportable-named-default proposal (sections 2.4.2 and 2.4.3), local
defaults should be merged into tcg_default, retaining any defaults
already present while overriding where necessary.

Key Changes:

* Introduce DefaultProvenance to track the origin of default declarations
  (local, imported, or built-in), replacing the original cd_module
  in ClassDefaults with cd_provenance :: DefaultProvenance.
* Rename tcDefaults to tcDefaultDecls, limiting its responsibility to only
  converting renamed class defaults into ClassDefaults.
* Add extendDefaultEnvWithLocalDefaults to merge local defaults into the
  environment, with proper duplication checks:
  - Duplicate local defaults for a class trigger an error.
  - Local defaults override imported or built-in defaults.
* Update and add related notes: Note [Builtin class defaults],
  Note [DefaultProvenance].
* Add regression tests: T25912, T25914, T25934.

Thanks sam and simon for the help on this patch.
Co-authored-by: sheaf <sam.derbyshire@gmail.com>

386f1854

by Teo Camarasu at 2025-04-17T04:31:55-04:00

template-haskell: Remove `addrToByteArrayName` and `addrToByteArray`

These were part of the implementation of the `Lift ByteArray` instance and were errornously exported because this module lacked an explicit export list. They have no usages on Hackage.

Resolves #24782

b96e2f77

by Sylvain Henry at 2025-04-18T20:46:33-04:00

RTS: remove target info and fix host info (#24058)

The RTS isn't a compiler, hence it doesn't have a target and we remove
the reported target info displayed by "+RTS --info". We also fix the
host info displayed by "+RTS --info": the host of the RTS is the
RTS-building compiler's target, not the compiler's host (wrong when
doing cross-compilation).

6d9965f4

by Sylvain Henry at 2025-04-18T20:46:33-04:00

RTS: remove build info

As per the discussion in !13967, there is no reason to tag the RTS with
information about the build platform.

d52e9b3f

by Vladislav Zavialov at 2025-04-18T20:47:15-04:00

Diagnostics: remove the KindMismatch constructor (#25957)

The KindMismatch constructor was only used as an intermediate
representation in pretty-printing.

Its removal addresses a problem detected by the "codes" test case:

  [GHC-89223] is untested (constructor = KindMismatch)

In a concious deviation from the usual procedure, the error code
GHC-89223 is removed entirely rather than marked as Outdated.
The reason is that it never was user-facing in the first place.

e2f2f9d0

by Vladislav Zavialov at 2025-04-20T10:53:39-04:00

Add name for -Wunusable-unpack-pragmas

This warning had no name or flag and was triggered unconditionally.
Now it is part of -Wdefault.

In GHC.Tc.TyCl.tcTyClGroupsPass's strict mode, we now have to
force-enable this warning to ensure that detection of flawed groups
continues to work even if the user disables the warning with the
-Wno-unusable-unpack-pragmas option. Test case: T3990c

Also, the misnamed BackpackUnpackAbstractType is now called
UnusableUnpackPragma.

6caa6508

by Adam Gundry at 2025-04-20T10:54:22-04:00

Fix specialisation of incoherent instances (fixes #25883)

GHC normally assumes that class constraints are canonical, meaning that
the specialiser is allowed to replace one dictionary argument with another
provided that they have the same type.  The `-fno-specialise-incoherents`
flag alters INCOHERENT instance definitions so that they will prevent
specialisation in some cases, by inserting `nospec`.

This commit fixes a bug in 7124e4ad76d98f1fc246ada4fd7bf64413ff2f2e, which
treated some INCOHERENT instance matches as if `-fno-specialise-incoherents`
was in effect, thereby unnecessarily preventing specialisation. In addition
it updates the relevant `Note [Rules for instance lookup]` and adds a new
`Note [Canonicity for incoherent matches]`.

0426fd6c
by Adam Gundry at 2025-04-20T10:54:23-04:00
```
Add regression test for #23429
```

eec96527

by Adam Gundry at 2025-04-20T10:54:23-04:00

user's guide: update specification of overlapping/incoherent instances

The description of the instance resolution algorithm in the user's
guide was slightly out of date, because it mentioned in-scope given
constraints only at the end, whereas the implementation checks for
their presence before any of the other steps.

This also adds a warning to the user's guide about the impact of
incoherent instances on specialisation, and more clearly documents
some of the other effects of `-XIncoherentInstances`.

a00eeaec

by Matthew Craven at 2025-04-20T10:55:03-04:00

Fix bytecode generation for `tagToEnum# <LITERAL>`

Fixes #25975.

ea5fab39

by Alan Zimmerman at 2025-04-21T18:44:33+01:00

GHC-CPP: first rough proof of concept

Processes

     #define FOO
     #ifdef FOO
     x = 1
     #endif

Into

    [ITcppIgnored [L loc ITcppDefine]
    ,ITcppIgnored [L loc ITcppIfdef]
    ,ITvarid "x"
    ,ITequal
    ,ITinteger (IL {il_text = SourceText "1", il_neg = False, il_value = 1})
    ,ITcppIgnored [L loc ITcppEndif]
    ,ITeof]

In time, ITcppIgnored will be pushed into a comment

e73abe65

by Alan Zimmerman at 2025-04-21T18:44:33+01:00

Tidy up before re-visiting the continuation mechanic

496b05a4

by Alan Zimmerman at 2025-04-21T18:44:33+01:00

Switch preprocessor to continuation passing style

Proof of concept, needs tidying up

7d770792
by Alan Zimmerman at 2025-04-21T18:44:33+01:00
```
Small cleanup
```
4436589a
by Alan Zimmerman at 2025-04-21T18:44:33+01:00
```
Get rid of some cruft
```

703f0997

by Alan Zimmerman at 2025-04-21T18:44:33+01:00

Starting to integrate.

Need to get the pragma recognised and set

d41cf158

by Alan Zimmerman at 2025-04-21T18:44:33+01:00

Make cppTokens extend to end of line, and process CPP comments

5473a8f8
by Alan Zimmerman at 2025-04-21T18:44:33+01:00
```
Remove unused ITcppDefined
```

6e761c77

by Alan Zimmerman at 2025-04-21T18:44:33+01:00

Allow spaces between # and keyword for preprocessor directive

a963ddf1

by Alan Zimmerman at 2025-04-21T18:44:33+01:00

Process CPP continuation lines

They are emited as separate ITcppContinue tokens.
Perhaps the processing should be more like a comment, and keep on
going to the end.
BUT, the last line needs to be slurped as a whole.

a27ddbe1

by Alan Zimmerman at 2025-04-21T18:44:33+01:00

Accumulate CPP continuations, process when ready

Can be simplified further, we only need one CPP token

aecedf1a

by Alan Zimmerman at 2025-04-21T18:44:33+01:00

Simplify Lexer interface. Only ITcpp

We transfer directive lines through it, then parse them from scratch
in the preprocessor.

a8124788

by Alan Zimmerman at 2025-04-21T18:44:33+01:00

Deal with directive on last line, with no trailing \n

07258013
by Alan Zimmerman at 2025-04-21T18:44:33+01:00
```
Start parsing and processing the directives
```
da41c32b
by Alan Zimmerman at 2025-04-21T18:44:33+01:00
```
Prepare for processing include files
```

74fc7700

by Alan Zimmerman at 2025-04-21T18:44:33+01:00

Move PpState into PreProcess

And initParserState, initPragState too

3629caba

by Alan Zimmerman at 2025-04-21T18:44:33+01:00

Process nested include files

Also move PpState out of Lexer.x, so it is easy to evolve it in a ghci
session, loading utils/check-cpp/Main.hs

30f795fb
by Alan Zimmerman at 2025-04-21T18:44:33+01:00
```
Split into separate files
```

fce63df8

by Alan Zimmerman at 2025-04-21T18:44:33+01:00

Starting on expression parser.

But it hangs. Time for Text.Parsec.Expr

a777ca97

by Alan Zimmerman at 2025-04-21T18:44:33+01:00

Start integrating the ghc-cpp work

From https://github.com/alanz/ghc-cpp

053eb592
by Alan Zimmerman at 2025-04-21T18:44:33+01:00
```
WIP
```
b71ec92e
by Alan Zimmerman at 2025-04-21T18:44:33+01:00
```
Fixup after rebase
```
e439eaa3
by Alan Zimmerman at 2025-04-21T18:44:33+01:00
```
WIP
```
c01bf5b6
by Alan Zimmerman at 2025-04-21T18:44:33+01:00
```
Fixup after rebase, including all tests pass
```
e0ba1ec8
by Alan Zimmerman at 2025-04-21T18:44:33+01:00
```
Change pragma usage to GHC_CPP from GhcCPP
```
c1b68436
by Alan Zimmerman at 2025-04-21T18:44:33+01:00
```
Some comments
```
dede9429
by Alan Zimmerman at 2025-04-21T18:44:33+01:00
```
Reformat
```
4eed4283
by Alan Zimmerman at 2025-04-21T18:44:33+01:00
```
Delete unused file
```
f2e37212
by Alan Zimmerman at 2025-04-21T18:44:33+01:00
```
Rename module Parse to ParsePP
```
45457d52
by Alan Zimmerman at 2025-04-21T18:44:33+01:00
```
Clarify naming in the parser
```

87c77e37

by Alan Zimmerman at 2025-04-21T18:44:33+01:00

WIP. Switching to alex/happy to be able to work in-tree

Since Parsec is not available

c529a377

by Alan Zimmerman at 2025-04-21T18:44:33+01:00

Layering is now correct

- GHC lexer, emits CPP tokens
- accumulated in Preprocessor state
- Lexed by CPP lexer, CPP command extracted, tokens concated with
  spaces (to get rid of token pasting via comments)
- if directive lexed and parsed by CPP lexer/parser, and evaluated

ebd2fd33

by Alan Zimmerman at 2025-04-21T18:44:33+01:00

First example working

Loading Example1.hs into ghci, getting the right results

```
{-# LANGUAGE GHC_CPP #-}
module Example1 where

y = 3

x =
  "hello"
  "bye now"

foo = putStrLn x
```

8537a9c0

by Alan Zimmerman at 2025-04-21T18:44:33+01:00

Rebase, and all tests pass except whitespace for generated parser

1807c3e1
by Alan Zimmerman at 2025-04-21T18:44:33+01:00
```
More plumbing. Ready for testing tomorrow.
```

d62a7992