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lib: Use lib.fixed-points.extends to avoid repetition #45394

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merged 1 commit into from Aug 20, 2018
Merged

lib: Use lib.fixed-points.extends to avoid repetition #45394

merged 1 commit into from Aug 20, 2018

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Ericson2314
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Motivation for this change

Another attempt after my sloppy 48ccdf3.

@infinisil, thanks again, reverted in 4794aa5 and explained my mistakes in 48ccdf3#commitcomment-29678643. I start with their work and provide this proof of this commit's correctness:

(lib.fixedPoints.extends (lib.flip g) f) # now
((f: rattrs: self: let super = rattrs self; in super // f self super) (lib.flip g) f) # inline extends
(self: let super = f self; in super // (lib.flip g) self super) # beta reduce
(self: let super = f self; in super // g super self)  # beta reduce
(self_: let super = f self_; in super // g super self_)  # alpha rename
(self_: let super = f self_; in super // g super self_) # original, same

Eventually we might harmonize overrideScope's g parameter with the general pattern, but I leave that breaking change as a separate step. Best not to refactor and break at once, and at least the abstractions make the oddity clearer.

Things done
  • Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
  • Built on platform(s)
    • NixOS
    • macOS
    • other Linux distributions
  • Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
  • Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
  • Tested execution of all binary files (usually in ./result/bin/)
  • Determined the impact on package closure size (by running nix path-info -S before and after)
  • Fits CONTRIBUTING.md.

lib: Use lib.fixed-points.extends to avoid repetition
3cf4354 
Another attempt after my sloppy 48ccdf3.

@infinisil, thanks again, reverted in 4794aa5 and explained my mistakes in 48ccdf3#commitcomment-29678643. I start with their work and provide this proof of this commit's correctness:
```nix
(lib.fixedPoints.extends (lib.flip g) f) # now
((f: rattrs: self: let super = rattrs self; in super // f self super) (lib.flip g) f) # inline extends
(self: let super = f self; in super // (lib.flip g) self super) # beta reduce
(self: let super = f self; in super // g super self)  # beta reduce
(self_: let super = f self_; in super // g super self_)  # alpha rename
(self_: let super = f self_; in super // g super self_) # original, same
```

Eventually we might harmonize `overrideScope`'s `g` parameter with the general pattern, but I leave that breaking change as a separate step. Best not to refactor and break at once, and at least the abstractions make the oddity clearer.
Ericson2314 referenced this pull request Aug 20, 2018
@Ericson2314
lib: Use lib.fixed-points.extends to avoid repetition
48ccdf3
Ericson2314 referenced this pull request Aug 20, 2018
@infinisil
Revert "lib: Use lib.fixed-points.extends to avoid repetition"
4794aa5 
This reverts commit 48ccdf3.
@Ericson2314 Ericson2314 merged commit f305b9b into master Aug 20, 2018
@Ericson2314 Ericson2314 deleted the makeScope-dry branch August 20, 2018 17:41
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@infinisil infinisil infinisil approved these changes

@edolstra edolstra Awaiting requested review from edolstra

@nbp nbp Awaiting requested review from nbp

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@Ericson2314 @infinisil @GrahamcOfBorg