piegames
7c76053d93
It being overridable was an intended feature with good use cases, and should not have been removed. However, this feature is generally in a bad state and needs revisiting in the future. Fixup for81d5f0a7d9Fixes #599 Change-Id:I2d93e012caa65aa795bce3a71d8e56d7052ef9df
19 lines
1.6 KiB
Markdown
19 lines
1.6 KiB
Markdown
---
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synopsis: Deprecated language features
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issues: [fj#437, 861]
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cls: [1785, 1736, 1735, 1744, 2206]
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category: Breaking Changes
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credits: [piegames, horrors]
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---
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A system for deprecation (and then the planned removal) of undesired language features has been put into place.
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It is controlled via feature flags much like experimental features, except that the deprecations are enabled default,
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and can be disabled via the flags for backwards compatibility (opt-out with `--extra-deprecated-features` or the Nix configuration file).
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- `url-literals`: **URL literals** have long been obsolete and discouraged of use, and now they are officially deprecated.
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This means that all URLs must be properly put within quotes like all other strings.
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- `rec-set-overrides`: **__overrides** is an old arcane syntax which has not been in use for more than a decade.
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It is soft-deprecated with a warning only, with the plan to turn that into an error in a future release.
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- `ancient-let`: **The old `let` syntax** (`let { body = …; … }`) is soft-deprecated with a warning as well. Use the regular `let … in` instead.
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- `shadow-internal-symbols`: Arithmetic expressions like `5 - 3` internally expand to `__sub 5 3`, where `__sub` maps to a subtraction builtin. Shadowing such a symbols would affect the evaluation of such operations, but in a very inconsistent way, and is therefore deprecated now. **Affected symbols are:** `__sub`, `__mul`, `__div`, `__lessThan`, and `__findFile`. Note that these symbols may still be used as variable names as long as they do not shadow internal operations, so e.g. `let __sub = x: y: x + y; in __sub 3 5` remains valid code.
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