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String slices as the keys of sendable maps bring about pain #3284

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pcwalton opened this issue Aug 26, 2012 · 4 comments
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String slices as the keys of sendable maps bring about pain #3284

pcwalton opened this issue Aug 26, 2012 · 4 comments
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A-lifetimes Area: Lifetimes / regions

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@pcwalton
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As far as I can see it, the region and slice systems make it impossible to use a send_map<&str,V>, unless you're only comparing static strings. The problem, as far as I can see it, is that find() wants to take its argument by reference, so the region checker requires invariance somehow and borrow check errors happen.

@nikomatsakis, thoughts? Maybe we need a separate StringMap type.
@pcwalton
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The other possibility is that we could have a ComparableTo<K> trait and a method find_related<Q:ComparableTo<K>>(&const self, +k: &Q), which gets rid of the need for a StringMap. That signature makes me very sad though.

The basic problem is that the query string isn't the same type as the strings inside the map...

@nikomatsakis
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Currently all type parameters are invariant. I have considered that a distinct StringMap could be useful. However, we could also apply the region variance inference to type parameters without big changes, which would be cool.

@Aatch Aatch mentioned this issue Apr 28, 2013
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@emberian
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@pcwalton as mentioned in #6095, find_equiv and Equiv present a solution to this.

Can be closed?

@thestinger
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@cmr: I think so, the problem is solved for HashMap since it uses equality

matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Oct 11, 2018
@matthiaskrgr
submodules: update clippy from 32b1d1f to 9d33731
89e824a 
Changes:

Remove now-useless `allow(unknown_lints)`
Stabilize tool lints
Use `impl Iterator` in arg position in clippy_dev
Fix fn_to_numeric_cast_with_truncation suppression
Limit commutative assign op lint to primitive types
Clarify code
Fix rust-lang#2937
Fix cast_possible_wrap and cast_sign_loss warnings
Fix cast_possible_truncation warnings
Fixes rust-lang#2925 cmp_owned false positive
if_let_redundant_pattern_matching: use Span.to() instead of Span.with_hi() to fix crash.
Improve diagnostics in case of lifetime elision (closes rust-lang#3284)
Fix items_after_statements for `const`s
Fix items_after_statements for sub-functions
Fix items_after_statements for `use` statements
Don't suggest cloned() for map Box deref
Fix excessive_precision false positive
Fix FP in `fn_to_numeric_cast_with_truncation`
new_without_default should not warn about unsafe new
fix command to manually test an example
Add license to README
Adding more detail to filter_map lint documentation.
additional people
Add license header to other files
Add license header to Rust files
Relicense clippy
Document relicensing process
Fix util/export.py to include lints from methods
matthiaskrgr added a commit to matthiaskrgr/rust that referenced this issue Oct 13, 2018
@matthiaskrgr
submodules: update clippy from 32b1d1f to 9d33731
ce61be8 
Changes:

Remove now-useless `allow(unknown_lints)`
Stabilize tool lints
Use `impl Iterator` in arg position in clippy_dev
Fix fn_to_numeric_cast_with_truncation suppression
Limit commutative assign op lint to primitive types
Clarify code
Fix rust-lang#2937
Fix cast_possible_wrap and cast_sign_loss warnings
Fix cast_possible_truncation warnings
Fixes rust-lang#2925 cmp_owned false positive
if_let_redundant_pattern_matching: use Span.to() instead of Span.with_hi() to fix crash.
Improve diagnostics in case of lifetime elision (closes rust-lang#3284)
Fix items_after_statements for `const`s
Fix items_after_statements for sub-functions
Fix items_after_statements for `use` statements
Don't suggest cloned() for map Box deref
Fix excessive_precision false positive
Fix FP in `fn_to_numeric_cast_with_truncation`
new_without_default should not warn about unsafe new
fix command to manually test an example
Add license to README
Adding more detail to filter_map lint documentation.
additional people
Add license header to other files
Add license header to Rust files
Relicense clippy
Document relicensing process
Fix util/export.py to include lints from methods
bors pushed a commit to rust-lang-ci/rust that referenced this issue May 15, 2021
@nrc
Merge pull request rust-lang#3284 from scampi/issue-3270
d2e91b5 
recognize strings inside comments in order to avoid indenting them
RalfJung pushed a commit to RalfJung/rust that referenced this issue Feb 25, 2024
@bors
Auto merge of rust-lang#3284 - RalfJung:little-endian-bitmask, r=Ralf…
f743422 
…Jung

enable from_bitmask_vector test on little-endian targets

Blocked on rust-lang/portable-simd#380 propagating to the rustc repo
jaisnan pushed a commit to jaisnan/rust-dev that referenced this issue Jul 29, 2024
@celinval
Fix TestLocalChain CI action (rust-lang#3284)
628ec4f 
Replace test used in workflow since we have deleted the function test. I
also made this action mandatory for our PRs.
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@nikomatsakis @pcwalton @emberian @thestinger