Implement `slice_strip` feature #73414

tesuji · 2020-06-16T16:08:59Z

Tracking issue: #73413

Mark-Simulacrum · 2020-06-16T16:14:25Z

Does making the impls here heterogeneous (i.e. impl<T> [T] { fn strip_prefix<U>(&self, prefix: &[U]); } hurt inference sufficiently that we don't want to do that?

jonas-schievink · 2020-06-16T16:16:04Z

Unsure why I'm assigned, I'm not on the libs team. r? @Mark-Simulacrum

tesuji · 2020-06-16T16:22:37Z

hurt inference sufficiently

I don't understand the question.
Why would we want this?

impl<T> [T] { 
    fn strip_prefix<U>(&self, prefix: &[U]); 
}

tesuji · 2020-06-16T16:25:34Z

Also, the strip_* methods somewhat copy the signature of slice::starts_with.

Does starts_with also cause problems?

pub fn starts_with(&self, needle: &[T]) -> bool

tesuji · 2020-06-17T16:15:10Z

r? @SimonSapin

tesuji · 2020-06-25T01:39:38Z

r? @dtolnay

dtolnay

Thanks! I am on board with this. It matches the method names on str and it matches the starts/ends_with signatures on slice.

dtolnay · 2020-06-25T05:48:54Z

@bors r+

bors · 2020-06-25T05:48:55Z

📌 Commit 560a996 has been approved by dtolnay

Implement `slice_strip` feature Tracking issue: rust-lang#73413

Manishearth · 2020-06-26T00:59:44Z

test time.rs - time::Duration::zero (line 145) ... ok
test unit.rs - unit::() (line 8) ... ok

failures:

---- slice/mod.rs - slice::[T]::strip_prefix (line 1468) stdout ----
error[E0308]: mismatched types
---- slice/mod.rs - slice::[T]::strip_suffix (line 1519) stdout ----
error[E0308]: mismatched types
 --> slice/mod.rs:1522:1
  |
6 | assert_eq!(v.strip_suffix(&[]), Some(v));
  | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected slice `[{integer}]`, found array `[{integer}; 3]`
  |
  = note: expected enum `std::option::Option<&[{integer}]>`
             found enum `std::option::Option<&[{integer}; 3]>`
  = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to previous error

For more information about this error, try `rustc --explain E0308`.
Couldn't compile the test.

failures:
    slice/mod.rs - slice::[T]::strip_prefix (line 1468)
    slice/mod.rs - slice::[T]::strip_prefix (line 1479)
    slice/mod.rs - slice::[T]::strip_suffix (line 1508)
    slice/mod.rs - slice::[T]::strip_suffix (line 1519)

test result: FAILED. 2600 passed; 4 failed; 28 ignored; 0 measured; 0 filtered out

#73733 (comment)

@bors r-

tesuji · 2020-06-26T01:54:38Z

src/libcore/slice/mod.rs

+    ///
+    /// ```
+    /// #![feature(slice_strip)]
+    /// let v = &[10, 40, 30];
+    /// assert_eq!(v.strip_prefix(&[]), Some(v));
+    /// let v: &[u8] = &[];
+    /// assert_eq!(v.strip_prefix(&[]), Some(v));
+    /// ```


Is this example needed?

I removed it.

dtolnay · 2020-06-28T23:15:25Z

src/libcore/slice/mod.rs

+    /// This method returns the original slice if `prefix` is an empty slice
+    /// or returns [`None`] if slice does not start with `prefix`.


I think the wording of this was clearer in a previous revision. Slice not starting with prefix is a scenario that is important to specify; this says what the meaning of Option in the return type is. Empty prefix is a small clarification (not even an edge case, since the behavior falls out from the rest of the documentation). I think the emphasis in this paragraph is backward and not conducive to recognizing the part that is more important.

I repharsed it. Could you take a look?

dtolnay · 2020-07-02T01:51:35Z

@bors r+

bors · 2020-07-02T01:51:37Z

📌 Commit cd9d833 has been approved by dtolnay

@ghost

…arth Rollup of 10 pull requests Successful merges: - rust-lang#73414 (Implement `slice_strip` feature) - rust-lang#73564 (linker: Create GNU_EH_FRAME header by default when producing ELFs) - rust-lang#73622 (Deny unsafe ops in unsafe fns in libcore) - rust-lang#73684 (add spans to injected coverage counters, extract with CoverageData query) - rust-lang#73812 (ast_pretty: Pass some token streams and trees by reference) - rust-lang#73853 (Add newline to rustc MultiSpan docs) - rust-lang#73883 (Compile rustdoc less often.) - rust-lang#73885 (Fix wasm32 being broken due to a NodeJS version bump) - rust-lang#73903 (Changes required for rustc/cargo to build for iOS targets) - rust-lang#73938 (Optimise fast path of checked_ops with `unlikely`) Failed merges: r? @ghost

rust-highfive assigned jonas-schievink Jun 16, 2020

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jun 16, 2020

tesuji mentioned this pull request Jun 16, 2020

Tracking Issue for slice_strip feature #73413

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rust-highfive assigned Mark-Simulacrum and unassigned jonas-schievink Jun 16, 2020

tesuji changed the title ~~Implement slice_strip feature~~ Implement slice_strip feature Jun 16, 2020

rust-highfive assigned SimonSapin and unassigned Mark-Simulacrum Jun 17, 2020

rust-highfive assigned dtolnay and unassigned SimonSapin Jun 25, 2020

dtolnay added the T-libs-api Relevant to the library API team, which will review and decide on the PR/issue. label Jun 25, 2020

dtolnay approved these changes Jun 25, 2020

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bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jun 25, 2020

Dylan-DPC-zz pushed a commit to Dylan-DPC-zz/rust that referenced this pull request Jun 25, 2020

Rollup merge of rust-lang#73414 - lzutao:slice_strip, r=dtolnay

4c558f5

Implement `slice_strip` feature Tracking issue: rust-lang#73413

Dylan-DPC-zz mentioned this pull request Jun 25, 2020

Rollup of 7 pull requests #73733

Closed

Manishearth added a commit to Manishearth/rust that referenced this pull request Jun 26, 2020

Rollup merge of rust-lang#73414 - lzutao:slice_strip, r=dtolnay

082cdf9

Implement `slice_strip` feature Tracking issue: rust-lang#73413

Manishearth mentioned this pull request Jun 26, 2020

Rollup of 14 pull requests #73744

Closed

Manishearth added a commit to Manishearth/rust that referenced this pull request Jun 26, 2020

Rollup merge of rust-lang#73414 - lzutao:slice_strip, r=dtolnay

2196bab

Implement `slice_strip` feature Tracking issue: rust-lang#73413

Manishearth mentioned this pull request Jun 26, 2020

Rollup of 15 pull requests #73745

Closed

bors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Jun 26, 2020

tesuji commented Jun 26, 2020

View reviewed changes

tesuji force-pushed the slice_strip branch 2 times, most recently from 83f5819 to 6068504 Compare June 26, 2020 03:51

dtolnay requested changes Jun 28, 2020

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Implement slice_strip feature

cd9d833

tesuji force-pushed the slice_strip branch from 6068504 to cd9d833 Compare July 1, 2020 12:37

tesuji requested a review from dtolnay July 1, 2020 12:39

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bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Jul 2, 2020

Manishearth mentioned this pull request Jul 2, 2020

Rollup of 10 pull requests #73954

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bors merged commit 63d392e into rust-lang:master Jul 2, 2020

tesuji deleted the slice_strip branch July 2, 2020 16:38

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Implement `slice_strip` feature #73414

Implement `slice_strip` feature #73414

tesuji commented Jun 16, 2020 •

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bors commented Jul 2, 2020

		/// This method returns the original slice if `prefix` is an empty slice
		/// or returns [`None`] if slice does not start with `prefix`.

Implement slice_strip feature #73414

Implement slice_strip feature #73414

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Implement `slice_strip` feature #73414

Implement `slice_strip` feature #73414

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