Partially implement type ascription by petrochenkov · Pull Request #30184 · rust-lang/rust

petrochenkov · 2015-12-03T03:01:23Z

This PR is a rebase of the original PR by @eddyb #21836 with some unrebasable parts manually reapplied, feature gate added + type equality restriction added as described below.

This implementation is partial because the type equality restriction is applied to all type ascription expressions and not only those in lvalue contexts. Thus, all difficulties with detection of these contexts and translation of coercions having effect in runtime are avoided.
So, you can't write things with coercions like let slice = &[1, 2, 3]: &[u8];. It obviously makes type ascription less useful than it should be, but it's still much more useful than not having type ascription at all.
In particular, things like let v = something.iter().collect(): Vec<_>; and let u = t.into(): U; work as expected and I'm pretty happy with these improvements alone.

Part of #23416

petrochenkov · 2015-12-03T10:06:22Z

Hm, @rust-highfive failed to assign a reviewer.

r? @eddyb

eddyb · 2015-12-03T12:18:27Z

I wrote the original version of this code, so I'd rather have someone else look over it.
r? @nikomatsakis

oli-obk · 2015-12-03T12:32:55Z

wrong indentation

bors · 2015-12-04T11:52:29Z

☔ The latest upstream changes (presumably #29850) made this pull request unmergeable. Please resolve the merge conflicts.

petrochenkov · 2015-12-04T23:16:45Z

Rebased.

bors · 2015-12-16T10:17:03Z

☔ The latest upstream changes (presumably #30206) made this pull request unmergeable. Please resolve the merge conflicts.

+ Apply parser changes manually + Add feature gate

petrochenkov · 2015-12-16T15:02:28Z

Rebased.

nikomatsakis · 2015-12-17T22:30:06Z

Sorry for the delay! I'll get to this soon.

nikomatsakis · 2015-12-18T09:34:04Z

This doesn't seem right. I think we probably want to convert this to a ExprKind::Cast.

/me reconsiders. Actually, let me read a bit more and get back to this point!

nikomatsakis · 2015-12-18T09:40:53Z

@petrochenkov I didn't notice at first that you skipped over the coercion aspect. Makes sense for a first pass, this certainly simplifies things. The code looks great. The only thing I would want to add are some parsing tests that test the relative precedence of : with other operators. Can you do that?

nikomatsakis · 2015-12-18T09:44:06Z

Some examples tests for precedence:

&[1, 2, 3]: &[u8; 3] => (&[1,2,3]): &[u8: 3]
x:u8+y => (22:u8)+42
x+y:u8 => x+(y:u8)

The only tricky part is how to write such at est. I envisioned testing this by setting up some scenarios that will fail to type-check if the precedence is not correct? I'm not sure if there is a better way.

petrochenkov · 2015-12-18T09:52:46Z

Sorry for the delay! I'll get to this soon.

Thanks! In fact my free time is coming to an end rapidly, so I have to wrap up my work on rustc ASAP (at least for now).
I'll add tests for operator precedence.

nikomatsakis · 2015-12-18T10:13:59Z

@petrochenkov

Thanks! In fact my free time is coming to an end rapidly, so I have to wrap up my work on rustc ASAP (at least for now).

:( Let me know if there is work you think you will not have time for! I'd be happy to land this PR (or privacy) and then do the followup work myself.

+ Rebase fixes

petrochenkov · 2015-12-18T17:01:32Z

Updated with the operator precedence tests.

nikomatsakis · 2015-12-19T01:54:46Z

@bors r+

Another nice PR. Thanks @petrochenkov!

bors · 2015-12-19T01:54:46Z

📌 Commit 95fdaf2 has been approved by nikomatsakis

bors · 2015-12-19T02:45:16Z

⌛ Testing commit 95fdaf2 with merge 440ef8b...

@eddyb

This PR is a rebase of the original PR by @eddyb #21836 with some unrebasable parts manually reapplied, feature gate added + type equality restriction added as described below. This implementation is partial because the type equality restriction is applied to all type ascription expressions and not only those in lvalue contexts. Thus, all difficulties with detection of these contexts and translation of coercions having effect in runtime are avoided. So, you can't write things with coercions like `let slice = &[1, 2, 3]: &[u8];`. It obviously makes type ascription less useful than it should be, but it's still much more useful than not having type ascription at all. In particular, things like `let v = something.iter().collect(): Vec<_>;` and `let u = t.into(): U;` work as expected and I'm pretty happy with these improvements alone. Part of #23416

bors · 2015-12-19T04:35:29Z

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-64-debug-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-x-android-t, auto-linux-cross-opt, auto-linux-musl-64-opt, auto-mac-32-opt, auto-mac-64-nopt-t, auto-mac-64-opt, auto-win-gnu-32-nopt-t, auto-win-gnu-32-opt, auto-win-gnu-64-nopt-t, auto-win-gnu-64-opt, auto-win-msvc-32-opt, auto-win-msvc-64-opt

petrochenkov · 2015-12-19T17:51:41Z

This should probably be marked with relnotes

brson · 2016-01-08T18:21:16Z

This ended up causing breakage in macros with multiple patterns.

rust-highfive assigned eddyb Dec 3, 2015

rust-highfive assigned nikomatsakis and unassigned eddyb Dec 3, 2015

oli-obk reviewed Dec 3, 2015
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Comment threadsrc/librustc_typeck/check/mod.rs Outdated
oli-obkDec 3, 2015
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wrong indentation

petrochenkov force-pushed the ascr branch from 8fd1579 to 96d2791Compare December 4, 2015 23:16

eddyband others added 2 commits December 16, 2015 17:12

Implement type ascription.
b8157cc

Add ExprType to HIR and make everything compile
e0ceef5
+ Apply parser changes manually + Add feature gate

petrochenkov force-pushed the ascr branch from 96d2791 to 7afc5e2Compare December 16, 2015 15:02

nikomatsakis reviewed Dec 18, 2015
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Require exact type equality + add tests
95fdaf2
+ Rebase fixes

petrochenkov force-pushed the ascr branch from 7afc5e2 to 95fdaf2Compare December 18, 2015 17:00

bors merged commit 95fdaf2 into rust-lang:masterDec 19, 2015

bors mentioned this pull request Dec 19, 2015
Improve ELF TLS detection on OSX #30417
Merged

eddyb added the relnotes Marks issues that should be documented in the release notes of the next release. label Dec 19, 2015

nikomatsakis mentioned this pull request Jan 19, 2016
Implement type ascription. #21836
Closed

kamalmarhubi mentioned this pull request Mar 2, 2016
Handle type ascription rust-lang/rustfmt#848
Closed

petrochenkov deleted the ascr branch September 21, 2016 19:44

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