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crater-report.md

Raw report

Analysis

Out of the 20 root regressions reported, the following are duds:

  • statistical-0.1.1: Duplicate of simple_stats.
  • volatile-register-0.1.1: Spurious failure
  • chipmunk-sys-0.0.4: Spurious failure.
  • shout-sys-0.1.1: Spurious failure.
  • scrutch-0.0.4: Spurious failure.
  • signify-0.3.0: Spurious failure.
  • google-civicinfo2-cli-0.3.6+20160823: Spurious failure.

There is one Deref-related failure which is fixed now in the implementation (using the suggested Deref impl from the RFC):

  • juniper-0.5.1: Deref coercion &String -> &str stops working

The new B parameter and constraints on or_insert caused one failure. This is fixed in the implementation now by moving the B parameter to the Entry types instead:

  • multimap-0.3.0: The new B parameter and constraints on insert

This means that, if we were to land the RFC right now, we'd have 11 regressions left. All of them have one-line fixes and they break down into the following categories:

  • rustc bugs:
    • difflib-0.1.0: rustc issue #37164
    • earth-0.0.2: rustc issue #37138
  • A local HashMap with reference key type can't have its type inferred anymore (see test case A). This is expected and mentioned in the RFC:
    • cargo-0.13.0
    • phf_macros-0.7.17
    • rustlex_fsa-0.3.3
    • simple_stats-0.1.1
  • Calls to string_map.entry(some_str.into()) are now ambiguous, since both conversions &str -> &str and &str -> String are valid.
    • hiirc-0.4.0
    • helianto-0.1.0-beta1
    • rustful-0.9.0
    • cargo-script-0.1.5
    • timmy-0.3.0

Analysis for each root regression

### cargo-0.13.0: Expected type inference failure: for map of references.

Fix: Type annotation on local map.

Crater

Code

Error:

   --> src/cargo/core/package_id_spec.rs:156:35
    |
156 |             let mut version_cnt = HashMap::new();
    |                                   ^^^^^^^^^^^^ cannot infer type for `_`
    |
    = note: type annotations or generic parameter binding required

Simplified test case:

use std::collections::HashMap;

fn test(state: &u32) -> Vec<u32> {
    let mut groups = Vec::new();
    let mut group_of_action /* : HashMap<&u32, _> */ = HashMap::new();
    groups.push(*group_of_action.entry(state).or_insert(0));
    groups
}

fn main() {}

phf_macros-0.7.17: Expected type inference failure: for map of references.

Fix: Add type annotation to local map.

Crater

Code

Error:

   --> src/lib.rs:340:23
    |
340 |     let mut strings = HashMap::new();
    |                       ^^^^^^^^^^^^ cannot infer type for `_`
    |

Simplified test case:

use std::collections::HashMap;

fn test(state: &u32) -> Vec<u32> {
    let mut groups = Vec::new();
    let mut group_of_action /* : HashMap<&u32, _> */ = HashMap::new();
    groups.push(*group_of_action.entry(state).or_insert(0));
    groups
}

fn main() {}

multimap-0.3.0: The new B parameter and constraints on insert.

This is a problem with my implementation. We need to sort this out either by adding the IntoOwned trait, or by somehow making the constraints 'global' for the Entry. Or by giving VacantEntry a function to produce a key.

Crater

Code

Error:

error[E0277]: the trait bound `K: std::cmp::Eq` is not satisfied
  --> src/entry.rs:86:25
   |
86 |         &mut self.inner.insert(vec![value])[0]
   |                         ^^^^^^ trait `K: std::cmp::Eq` not satisfied
   |
   = help: consider adding a `where K: std::cmp::Eq` bound
error[E0277]: the trait bound `K: std::hash::Hash` is not satisfied
  --> src/entry.rs:92:20
   |
92 |         self.inner.insert(values)
   |                    ^^^^^^ trait `K: std::hash::Hash` not satisfied
   |
   = help: consider adding a `where K: std::hash::Hash` bound
error[E0277]: the trait bound `K: std::cmp::Eq` is not satisfied
  --> src/entry.rs:92:20
   |
92 |         self.inner.insert(values)
   |                    ^^^^^^ trait `K: std::cmp::Eq` not satisfied
   |
   = help: consider adding a `where K: std::cmp::Eq` bound

Simplified test case:

use std::collections::HashMap;
use std::collections::hash_map::VacantEntry;

fn insert<'a, K: 'a, V: 'a>(entry: VacantEntry<'a, K, V>, value: V) {
    entry.insert(value);
}

fn main() {}

volatile-register-0.1.1: Spurious failure

[Crater](https://tools.taskcluster.net/task-inspector/#9M0KEiOyRBSsD_Uv40tMjA/0)

rustlex_fsa-0.3.3: Expected type inference failure: for map of references

Fix: Add type annotation to local map.

Crater

Code

Error:

   --> dfa.rs:115:35
    |
115 |         let mut group_of_action = HashMap::new();
    |                                   ^^^^^^^^^^^^ cannot infer type for `_`
    |
    = note: type annotations or generic parameter binding required

Simplified test case:

use std::collections::HashMap;

fn test(state: &u32) -> Vec<u32> {
    let mut groups = Vec::new();
    let mut group_of_action /* : HashMap<&u32, _> */ = HashMap::new();
    groups.push(*group_of_action.entry(state).or_insert(0));
    groups
}

fn main() {}

shout-sys-0.1.1: Spurious failure.

[Crater](https://tools.taskcluster.net/task-inspector/#WUkEgcnCQnOxqL-wOAUBWA/0)

hiirc-0.4.0: Expected type inference failure: for key.into().

Fix: Change .into() to to_string()/to_owned().

Crater

Code

Error:

   --> src/core.rs:332:39
    |
332 |         self.channels.lock().unwrap().entry(id.into()).or_insert(Arc::new(Channel::new(name)));
    |                                       ^^^^^ cannot infer type for `_`
    |
    = note: type annotations or generic parameter binding required

Simplified test case:

use std::collections::hashmap;

fn test() {
    let mut deps: hashmap<string, string> = hashmap::new();
    let name = "";
    match deps.entry(name.into()) {
        _ => {}
    }
}

fn main() {}

statistical-0.1.1: Duplicate of simple_stats.

chipmunk-sys-0.0.4: Spurious failure.

[Crater](https://tools.taskcluster.net/task-inspector/#vmzYbHh6R5ShkeUDYeA6kQ/0)

helianto-0.1.0-beta1: Expected type inference failure: for key.into().

Fix: Change .into() to to_string()/to_owned().

Crater

Code

Error:

 --> src/generators/index.rs:42:44
   |
42 |                     Some(string) => string.into(),
   |                                            ^^^^ trait `(): std::convert::From<&str>` not satisfied
   |
   = note: required because of the requirements on the impl of `std::convert::Into<()>` for `&str`
error[E0277]: the trait bound `(): std::borrow::AsBorrowOf` is not satisfied
  --> src/generators/index.rs:46:41
   |
46 |                 let documents = indexes.entry(index_url).or_insert_with(Vec::new);
   |                                         ^^^^^ trait `(): std::borrow::AsBorrowOf` not satisfied
error[E0277]: the trait bound `(): std::borrow::AsBorrowOf` is not satisfied
  --> src/generators/index.rs:46:58
   |
46 |                 let documents = indexes.entry(index_url).or_insert_with(Vec::new);
   |                                                          ^^^^^^^^^^^^^^ trait `(): std::borrow::AsBorrowOf` not satisfied

Simplified test case:

use std::collections::hashmap;

fn test() {
    let mut deps: hashmap<string, string> = hashmap::new();
    let name = "";
    match deps.entry(name.into()) {
        _ => {}
    }
}

fn main() {}

juniper-0.5.1: Deref coercion &String -> &str stops working.

Fix: use specialisation version in the RFC or change to key[..].

Crater

Code

Error:

error[E0271]: type mismatch resolving `::Owned == &'a str`
  --> src/validation/rules/unique_variable_names.rs:23:26
   |
23 |         match self.names.entry(&var_name.item) {
   |                          ^^^^^ expected struct `std::string::String`, found reference
   |
   = note: expected type `std::string::String`
   = note:    found type `&'a str`
error[E0277]: the trait bound `&str: std::borrow::Borrow` is not satisfied
  --> src/validation/rules/unique_variable_names.rs:30:19
   |
30 |                 e.insert(var_name.start.clone());
   |                   ^^^^^^ trait `&str: std::borrow::Borrow` not satisfied
error[E0271]: type mismatch resolving `::Owned == &str`
  --> src/validation/rules/unique_variable_names.rs:30:19
   |
30 |                 e.insert(var_name.start.clone());
   |                   ^^^^^^ expected struct `std::string::String`, found &str
   |
   = note: expected type `std::string::String`
   = note:    found type `&str`

Simplified test case:

use std::collections::HashMap;

fn test<'a>(key: &'a String) {
    let mut map: HashMap<&'a str, u32> = HashMap::new();
    map.entry(key);
}

fn main() {}

difflib-0.1.0: rustc issue #37164

Fix:

  • Fix rustc issue
  • This fails due to an interaction between auto-deref and inference (it would have failed today if it used get instead of entry). The solution is to deref element in the call: if (self.is_junk.unwrap())(*element).

Crater

Code

Error:

   --> src/sequencematcher.rs:149:55
    |
149 | 	for (element, indexes) in second_sequence_elements.iter() {
    | 			                                                   ^^^^
    |
    = note: the method `iter` exists but the following trait bounds were not satisfied: `str : std::marker::Sized`
error: no method named `remove` found for type `std::collections::HashMap>` in the current scope
   --> src/sequencematcher.rs:155:30
    |
155 | 	second_sequence_elements.remove(element);
    | 				                         ^^^^^^
    |
    = note: the method `remove` exists but the following trait bounds were not satisfied: `str : std::marker::Sized`
error[E0308]: mismatched types
   --> src/sequencematcher.rs:158:35
    |
158 | 	self.second_sequence_elements = second_sequence_elements;
    | 		                                ^^^^^^^^^^^^^^^^^^^^^^^^ expected reference, found str
    |
    = note: expected type `std::collections::HashMap<&'a str, std::vec::Vec>`
    = note:    found type `std::collections::HashMap>`

Simplified test case:

use std::collections::HashMap;

fn is_junk(_: &str) -> bool { false }

fn chain_second_seq<'a>(x: &'a str) -> HashMap<&'a str, Vec<usize>> {
    let mut second_sequence_elements = HashMap::new();
    second_sequence_elements.entry(x);
    if is_junk(second_sequence_elements.keys().next().unwrap()) {}
    second_sequence_elements
}

fn main() {}

earth-0.0.2: rustc issue #37138

Fix:

  • Fix rustc issue.
  • Add the redundant constraint to workaround the bug K: Borrow<K>, in this case the mouthful: <<T as Entity>::Id as ToOwned>::Owned: Borrow<<<T as Entity>::Id as ToOwned>::Owned>.

Crater

Code

Error:

error[E0277]: the trait bound `::Id: std::cmp::Eq` is not satisfied
  --> src/schema.rs:94:31
   |
94 |             match identifiers.entry(eid) {
   |                               ^^^^^ trait `::Id: std::cmp::Eq` not satisfied
   |
   = help: consider adding a `where ::Id: std::cmp::Eq` bound
error[E0277]: the trait bound `::Id: std::marker::Sized` is not satisfied
  --> src/schema.rs:94:31
   |
94 |             match identifiers.entry(eid) {
   |                               ^^^^^ trait `::Id: std::marker::Sized` not satisfied
   |
   = help: consider adding a `where ::Id: std::marker::Sized` bound
error[E0277]: the trait bound `<::Id as std::borrow::ToOwned>::Owned: std::borrow::AsBorrowOf<<::Id as std::borrow::ToOwned>::Owned, ::Id>` is not satisfied
  --> src/schema.rs:94:31
   |
94 |             match identifiers.entry(eid) {
   |                               ^^^^^ trait `<::Id as std::borrow::ToOwned>::Owned: std::borrow::AsBorrowOf<<::Id as std::borrow::ToOwned>::Owned, ::Id>` not satisfied
   |
   = help: consider adding a `where <::Id as std::borrow::ToOwned>::Owned: std::borrow::AsBorrowOf<<::Id as std::borrow::ToOwned>::Owned, ::Id>` bound
error: aborting due to 4 previous errors

Simplified test case:

use std::collections::HashMap;
use std::hash::Hash;
use std::borrow::Cow;

// Remove the commented out constraint to fix (NB that T: Borrow<T>).
fn merge<T: ToOwned + ?Sized>(entity_id: Cow<T>)
        where T::Owned: Hash + Eq /* + ::std::borrow::Borrow<T::Owned> */ {
    let mut identifiers: HashMap<T::Owned, u32> = HashMap::new();
    let eid = entity_id.into_owned();
    match identifiers.entry(eid) {
        _ => {}
    }
}

fn main() {}

rustful-0.9.0: Expected type inference failure: for key.into().

Fix: use From instead of into: MaybeUtf8Owned::from(key.to_owned()).

Crater

Code

Error:

  --> src/router/tree_router.rs:72:38
   |
72 |             match self.static_routes.entry(key.to_owned().into()) {
   |                                      ^^^^^ cannot infer type for `_`
   |
   = note: type annotations or generic parameter binding required

Simplified test case:

use std::collections::HashMap;
use std::borrow::Cow;

fn find_or_insert_router<'a>(static_routes: HashMap<Cow<[u8]>, u32>, key: &[u8]) {
    match static_routes.entry(key.to_owned().into()) {
        _ => {},
    }
}

fn main() {}

scrutch-0.0.4: Spurious failure.

[Crater](https://tools.taskcluster.net/task-inspector/#0TPi_1V_SoyVBvdnSULv3w/0)

signify-0.3.0: Spurious failure.

[Crater](https://tools.taskcluster.net/task-inspector/#sAU50vqCQ1mpoReQbLNHDA/0)

simple_stats-0.1.1: Expected type inference failure: for map of references

Fix: Add type annotation to local map.

Crater

Code

Error:

error: the type of this value must be known in this context
  --> src/univariate_.rs:73:33
   |
73 |                     mode = Some(**val);
   |                                 ^^^^^

Simplified test case:

use std::collections::HashMap;

pub fn mode(v: &[u32]) -> Option<u32> {
    let mut counter = HashMap::new();
    let mut mode = None;
    for x in v.iter() {
        *counter.entry(x).or_insert(0) += 1;
    }
    for (val, _) in &counter {
        mode = Some(**val);
    }
    mode
}

fn main() {}

cargo-script-0.1.5: Expected type inference failure: for key.into()

Fix: change `.into()` to `to_string()`/`to_owned()`.

Crater

Code

Error:

  --> src/main.rs:376:24
    |
376 |             match deps.entry(name.into()) {
    |                        ^^^^^ cannot infer type for `_`
    |
    = note: type annotations or generic parameter binding required

Simplified test case:

use std::collections::HashMap;

fn test() {
    let mut deps: HashMap<String, String> = HashMap::new();
    let name = "";
    match deps.entry(name.into()) {
        _ => {}
    }
}

fn main() {}

timmy-0.3.0: Expected type inference failure: for key.into()

Fix: change `.into()` to `to_string()`/`to_owned()`.

Crater

Code

Error:

error[E0282]: unable to infer enough type information about `_`
   --> src/main.rs:177:13
    |
177 |         let mut current_program = get_current_program().trim().into();
    |             ^^^^^^^^^^^^^^^^^^^ cannot infer type for `_`
    |
    = note: type annotations or generic parameter binding required

Simplified test case:

use std::collections::HashMap;

fn test() -> HashMap<String, i64> {
    let mut map = HashMap::new();
    let key = "".into();
    map.entry(key);
    map
}

fn main() {}

google-civicinfo2-cli-0.3.6+20160823: Spurious failure.

[Crater](https://tools.taskcluster.net/task-inspector/#P1Hq0nojTxumY9TnLgoyhQ/0)
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