be29bcd402
This fixes type resolution for `iterable[T]`. I want to proceed with RFC [#562](https://github.com/nim-lang/RFCs/issues/562) and this is the main blocker for composability. Fixes #22098 and, arguably, #19206 ```nim import std/strutils template collect[T](it: iterable[T]): seq[T] = block: var res: seq[T] = @[] for x in it: res.add x res const text = "a b c d" let words = text.split.collect() doAssert words == @[ "a", "b", "c", "d" ] ``` In cases like `strutils.split`, where both proc and iterator overload exists, the compiler resolves to the `func` overload causing a type mismatch. The old mode resolved `text.split` to `seq[string]` before the surrounding `iterable[T]` requirement was applied, so the argument no longer matched this template. It should be noted that, compared to older sequtils templates, composable chains based on `iterable[T]` require an iterator-producing expression, e.g. `"foo".items.iterableTmpl()` rather than just `"foo".iterableTmpl()`. This is actually desirable: it keeps the iteration boundary explicit and makes iterable-driven templates intentionally not directly interchangeable with older untyped/loosely-typed templates like those in `sequtils`, whose internal iterator setup we have zero control over (e.g. hard-coding adapters like `items`). Also, I noticed in `semstmts` that anonymous iterators are always `closure`, which is not that surprising if you think about it, but still I added a paragraph to the manual. Regarding implementation: From what I gathered, the root cause is that `semOpAux` eagerly pre-types all arguments with plain flags before overload resolution begins, so by the time `prepareOperand` processes `split` against the `iterable[T]`, the wrong overload has already won. The fix touches a few places: - `prepareOperand` in `sigmatch.nim`: When `formal.kind == tyIterable` and the argument was already typed as something else, it's re-semchecked with the `efPreferIteratorForIterable` flag. The recheck is limited to direct calls (`a[0].kind in {nkIdent, nkAccQuoted, nkSym, nkOpenSym}`) to avoid recursing through `semIndirectOp`/`semOpAux` again. - `iteratorPreference` field `TCandidate`, checked before `genericMatches` in `cmpCandidates`, gives the iterator overload a win without touching the existing iterator heuristic used by `for` loops. **Limitations:** The implementation is still flag-driven rather than purely formal-driven, so the behaviour is a bit too broad `efWantIterable` can cause iterator results to be wrapped as `tyIterable` in iterable-admitting contexts, not only when `iterable[T]` match is being processed. `iterable[T]` still does not accept closure iterator values such as`iterator(): T {.closure.}`. It only matches the compiler's internal `tyIterable`, not arbitrary iterator-typed values. The existing iterator-preference heuristic is still in place, because when I tried to remove it, some loosely-related regressions happened. In particular, ordinary iterator-admitting contexts and iterator chains still rely on early iterator preference during semchecking, before the compiler has enough surrounding context to distinguish between value/iterator producing overloads. Full heuristic removal would require a broader refactor of dot-chain/intermediate-expression semchecking, which is just too much for me ATM. This PR narrows only the tyIterable-specific cases. **Future work:** Rework overload resolution to preserve additional information of matching iterator overloads for calls up to the point where the iterator-requiring context is established, to avoid re-sem in `prepareOperand`. Currently there's no good channel to store that information. Nodes can get rewritten, TCandidate doesn't live long enough, storing in Context or some side-table raises the question how to properly key that info.
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_v3 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.
Backers
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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 © 2006-2026 Andreas Rumpf, all rights reserved.