525d64fe88
fixes #24887 (really just this [1 line
commit](632c7b3397)
would have been enough to fix the issue but it would ignore the general
problem)
When a type definition is encountered where the symbol already has a
type (not a forward type), the type is left alone (not reset to
`tyForward`) and the RHS is handled differently: The RHS is still
semchecked, but the type of the symbol is not updated, and nominal type
nodes are ignored entirely (specifically if they are the same kind as
the symbol's existing type but this restriction is not really needed).
If the existing type of the symbol is an enum and and the RHS has a
nominal enum type node, the enum fields of the existing type are added
to scope rather than creating a new type from the RHS and adding its
symbols instead.
The goal is to prevent any incompatible nominal types from being
generated during resem as in #24887. But it also restricts what macros
can do if they generate type section AST, for example if we have:
```nim
type Foo = int
```
and a macro modifies the type section while keeping the symbol node for
`Foo` like:
```nim
type Foo = float
```
Then the type of `Foo` will still remain `int`, while it previously
became `float`. While we could maybe allow this and make it so only
nominal types cannot be changed, it gets even more complex when
considering generic params and whether or not they get updated. So to
keep it as simple as possible the rule is that the symbol type does not
change, but maybe this behavior was useful for macros.
Only nominal type nodes are ignored for semchecking on the RHS, so that
cases like this do not cause a regression:
```nim
template foo(): untyped =
proc bar() {.inject.} = discard
int
type Foo = foo()
bar() # normally works
```
However this specific code exposed a problem with forward type handling:
---
In specific cases, when the type section is undergoing the final pass,
if the type fits some overly general criteria (it is not an object,
enum, alias or a sink type and its node is not a nominal type node), the
entire RHS is semchecked for a 2nd time as a standalone type (with `nil`
prev) and *maybe* reassigned to the new semchecked type, depending on
its type kind. (for some reason including nominal types when we excluded
them before?) This causes a redefinition error if the RHS defines a
symbol.
This code goes all the way back to the first commit and I could not find
the reason why it was there, but removing it showed a failure in
`thard_tyforward`: If a generic forward type is invoked, it is left as
an unresolved `tyGenericInvocation` on the first run. Semchecking it
again at the end turns it into a `tyGenericInst`. So my understanding is
that it exists to handle these loose forward types, but it is way too
general and there is a similar mechanism `c.skipTypes` which is supposed
to do the same thing but doesn't.
So this is no longer done, and `c.skipTypes` is revamped (and renamed):
It is now a list of types and the nodes that are supposed to evaluate to
them, such that types needing to be updated later due to containing
forward types are added to it along with their nodes. When finishing the
type section, these types are reassigned to the semchecked value of
their nodes so that the forward types in them are fully resolved. The
"reassigning" here works due to updating the data inside the type
pointer directly, and is how forward types work by themselves normally
(`tyForward` types are modified in place as `s.typ`).
For example, as mentioned before, generic invocations of forward types
are first created as `tyGenericInvocation` and need to become
`tyGenericInst` later. So they are now added to this list along with
their node. Object types with forward types as their base types also
need to be updated later to check that the base type is correct/inherit
fields from it: For this the entire object type and its node are added
to the list. Similarly, any case where whether a component type is
`tyGenericInst` or `tyGenericInvocation` matters also needs to cascade
this (`set` does presumably to check the instantiated type).
This is not complete: Generic invocations with forward types only check
that their base type is a forward type, but not any of their arguments,
which causes #16754 and #24133. The generated invocations also need to
cascade properly: `Foo[Bar[ForwardType]]` for example would see that
`Bar[ForwardType]` is a generic invocation and stay as a generic
invocation itself, but it might not queue itself to be updated later.
Even if it did, only the entire type `Foo[Bar[ForwardType]]` needs to be
queued, updating `Bar[ForwardType]` by itself would be redundant or it
would not change anything at all. But these can be done later.
Nim
This repository contains the Nim compiler, Nim's stdlib, tools, and documentation. For more information about Nim, including downloads and documentation for the latest release, check out Nim's website or bleeding edge docs.
Community
- The forum - the best place to ask questions and to discuss Nim.
- #nim IRC Channel (Libera Chat) - a place to discuss Nim in real-time. Also where most development decisions get made.
- Discord - an additional place to discuss Nim in real-time. Most channels there are bridged to IRC.
- Gitter - an additional place to discuss Nim in real-time. There is a bridge between Gitter and the IRC channel.
- Matrix - the main room to discuss Nim in real-time. Matrix space contains a list of rooms, most of them are bridged to IRC.
- Telegram - an additional place to discuss Nim in real-time. There is the official Telegram channel. Not bridged to IRC.
- Stack Overflow - a popular Q/A site for programming related topics that includes posts about Nim.
- GitHub Wiki - Misc user-contributed content.
Compiling
The compiler currently officially supports the following platform and architecture combinations:
| Operating System | Architectures Supported |
|---|---|
| Windows (Windows XP or greater) | x86 and x86_64 |
| Linux (most distributions) | x86, x86_64, ppc64, and armv6l |
| Mac OS X (10.04 or greater) | x86, x86_64, ppc64, and Apple Silicon (ARM64) |
More platforms are supported, however, they are not tested regularly and they may not be as stable as the above-listed platforms.
Compiling the Nim compiler is quite straightforward if you follow these steps:
First, the C source of an older version of the Nim compiler is needed to
bootstrap the latest version because the Nim compiler itself is written in the
Nim programming language. Those C sources are available within the
nim-lang/csources_v2 repository.
Next, to build from source you will need:
- A C compiler such as
gcc6.x/later or an alternative such asclang,Visual C++orIntel C++. It is recommended to usegcc6.x or later. - Either
gitorwgetto download the needed source repositories. - The
build-essentialpackage when usinggccon Ubuntu (and likely other distros as well). - On Windows MinGW 4.3.0 (GCC 8.10) is the minimum recommended compiler.
- Nim hosts a known working MinGW distribution:
Windows Note: Cygwin and similar POSIX runtime environments are not supported.
Then, if you are on a *nix system or Windows, the following steps should compile
Nim from source using gcc, git, and the koch build tool.
Note: The following commands are for the development version of the compiler. For most users, installing the latest stable version is enough. Check out the installation instructions on the website to do so: https://nim-lang.org/install.html.
For package maintainers: see packaging guidelines.
First, get Nim from GitHub:
git clone https://github.com/nim-lang/Nim.git
cd Nim
Next, run the appropriate build shell script for your platform:
build_all.sh(Linux, Mac)build_all.bat(Windows)
Finally, once you have finished the build steps (on Windows, Mac, or Linux) you
should add the bin directory to your PATH.
See also bootstrapping the compiler.
See also reproducible builds.
Koch
koch is the build tool used to build various parts of Nim and to generate
documentation and the website, among other things. The koch tool can also
be used to run the Nim test suite.
Assuming that you added Nim's bin directory to your PATH, you may execute
the tests using ./koch tests. The tests take a while to run, but you
can run a subset of tests by specifying a category (for example
./koch tests cat async).
For more information on the koch build tool please see the documentation
within the doc/koch.md file.
Nimble
nimble is Nim's package manager. To learn more about it, see the
nim-lang/nimble repository.
Contributors
This project exists thanks to all the people who contribute.
Contributing
See detailed contributing guidelines. We welcome all contributions to Nim regardless of how small or large they are. Everything from spelling fixes to new modules to be included in the standard library are welcomed and appreciated. Before you start contributing, you should familiarize yourself with the following repository structure:
bin/,build/- these directories are empty, but are used when Nim is built.compiler/- the compiler source code. Also includes plugins withincompiler/plugins.nimsuggest- the nimsuggest tool that previously lived in thenim-lang/nimsuggestrepository.config/- the configuration for the compiler and documentation generator.doc/- the documentation files in reStructuredText format.lib/- the standard library, including:pure/- modules in the standard library written in pure Nim.impure/- modules in the standard library written in pure Nim with dependencies written in other languages.wrappers/- modules that wrap dependencies written in other languages.
tests/- contains categorized tests for the compiler and standard library.tools/- the tools includingniminst(mostly invoked viakoch).koch.nim- the tool used to bootstrap Nim, generate C sources, build the website, and generate the documentation.
If you are not familiar with making a pull request using GitHub and/or git, please read this guide.
Ideally, you should make sure that all tests pass before submitting a pull request.
However, if you are short on time, you can just run the tests specific to your
changes by only running the corresponding categories of tests. CI verifies
that all tests pass before allowing the pull request to be accepted, so only
running specific tests should be harmless.
Integration tests should go in tests/untestable.
If you're looking for ways to contribute, please look at our issue tracker.
There are always plenty of issues labeled Easy; these should
be a good starting point for an initial contribution to Nim.
You can also help with the development of Nim by making donations. Donations can be made using:
If you have any questions feel free to submit a question on the Nim forum, or via IRC on the #nim channel.
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You can also see a list of all our sponsors/backers from various payment services on the sponsors page of our website.
License
The compiler and the standard library are licensed under the MIT license, except for some modules which explicitly state otherwise. As a result, you may use any compatible license (essentially any license) for your own programs developed with Nim. You are explicitly permitted to develop commercial applications using Nim.
Please read the copying.txt file for more details.
Copyright © 2006-2025 Andreas Rumpf, all rights reserved.