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Rollup merge of #76135 - CDirkx:const-option, r=dtolnay,oli-obk 

Stabilize some Option methods as const

Stabilize the following methods of `Option` as const:
 - `is_some`
 - `is_none`
 - `as_ref`

These methods are currently const under the unstable feature `const_option` (tracking issue: #67441).
I believe these methods to be eligible for stabilization because of the stabilization of #49146 (Allow if and match in constants) and the trivial implementations, see also:  [PR#75463](https://github.com/rust-lang/rust/pull/75463).

Related: #76225
This commit is contained in:
Ralf Jung 2020-09-21 10:40:26 +02:00 committed by GitHub
parent a409a233e0 43cba349bd
commit c3abb82908
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GPG Key ID: 4AEE18F83AFDEB23
7 changed files with 128 additions and 146 deletions
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6
library/core/src/option.rs
View File

@ -175,7 +175,7 @@ impl<T> Option<T> {
/// ```
#[must_use = "if you intended to assert that this has a value, consider `.unwrap()` instead"]
#[inline]
#[rustc_const_unstable(feature = "const_option", issue = "67441")]
#[rustc_const_stable(feature = "const_option", since = "1.48.0")]
#[stable(feature = "rust1", since = "1.0.0")]
pub const fn is_some(&self) -> bool {
matches!(*self, Some(_))
@ -195,7 +195,7 @@ impl<T> Option<T> {
#[must_use = "if you intended to assert that this doesn't have a value, consider \
`.and_then(|| panic!(\"`Option` had a value when expected `None`\"))` instead"]
#[inline]
#[rustc_const_unstable(feature = "const_option", issue = "67441")]
#[rustc_const_stable(feature = "const_option", since = "1.48.0")]
#[stable(feature = "rust1", since = "1.0.0")]
pub const fn is_none(&self) -> bool {
!self.is_some()
@ -254,7 +254,7 @@ impl<T> Option<T> {
/// println!("still can print text: {:?}", text);
/// ```
#[inline]
#[rustc_const_unstable(feature = "const_option", issue = "67441")]
#[rustc_const_stable(feature = "const_option", since = "1.48.0")]
#[stable(feature = "rust1", since = "1.0.0")]
pub const fn as_ref(&self) -> Option<&T> {
match *self {

16
library/core/tests/option.rs
View File

@ -356,3 +356,19 @@ fn test_replace() {
assert_eq!(x, Some(3));
assert_eq!(old, None);
}
#[test]
fn option_const() {
// test that the methods of `Option` are usable in a const context
const OPTION: Option<usize> = Some(32);
const REF: Option<&usize> = OPTION.as_ref();
assert_eq!(REF, Some(&32));
const IS_SOME: bool = OPTION.is_some();
assert!(IS_SOME);
const IS_NONE: bool = OPTION.is_none();
assert!(!IS_NONE);
}

14
src/test/ui/consts/const-option.rs
View File

@ -1,14 +0,0 @@
// run-pass
#![feature(const_option)]
const X: Option<i32> = Some(32);
const Y: Option<&i32> = X.as_ref();
const IS_SOME: bool = X.is_some();
const IS_NONE: bool = Y.is_none();
fn main() {
assert!(IS_SOME);
assert!(!IS_NONE)
}

78
src/tools/clippy/clippy_lints/src/matches.rs
View File

@ -1440,15 +1440,12 @@ where
mod redundant_pattern_match {
use super::REDUNDANT_PATTERN_MATCHING;
use crate::utils::{in_constant, match_qpath, match_trait_method, paths, snippet, span_lint_and_then};
use crate::utils::{match_qpath, match_trait_method, paths, snippet, span_lint_and_then};
use if_chain::if_chain;
use rustc_ast::ast::LitKind;
use rustc_errors::Applicability;
use rustc_hir::{Arm, Expr, ExprKind, HirId, MatchSource, PatKind, QPath};
use rustc_hir::{Arm, Expr, ExprKind, MatchSource, PatKind, QPath};
use rustc_lint::LateContext;
use rustc_middle::ty;
use rustc_mir::const_eval::is_const_fn;
use rustc_span::source_map::Symbol;
pub fn check<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
if let ExprKind::Match(op, arms, ref match_source) = &expr.kind {
@ -1468,37 +1465,24 @@ mod redundant_pattern_match {
arms: &[Arm<'_>],
keyword: &'static str,
) {
fn find_suggestion(cx: &LateContext<'_>, hir_id: HirId, path: &QPath<'_>) -> Option<&'static str> {
if match_qpath(path, &paths::RESULT_OK) {
return Some("is_ok()");
}
if match_qpath(path, &paths::RESULT_ERR) {
return Some("is_err()");
}
if match_qpath(path, &paths::OPTION_SOME) && can_suggest(cx, hir_id, sym!(option_type), "is_some") {
return Some("is_some()");
}
if match_qpath(path, &paths::OPTION_NONE) && can_suggest(cx, hir_id, sym!(option_type), "is_none") {
return Some("is_none()");
}
None
}
let hir_id = expr.hir_id;
let good_method = match arms[0].pat.kind {
PatKind::TupleStruct(ref path, ref patterns, _) if patterns.len() == 1 => {
if let PatKind::Wild = patterns[0].kind {
find_suggestion(cx, hir_id, path)
if match_qpath(path, &paths::RESULT_OK) {
"is_ok()"
} else if match_qpath(path, &paths::RESULT_ERR) {
"is_err()"
} else if match_qpath(path, &paths::OPTION_SOME) {
"is_some()"
} else {
return;
}
} else {
None
return;
}
},
PatKind::Path(ref path) => find_suggestion(cx, hir_id, path),
_ => None,
};
let good_method = match good_method {
Some(method) => method,
None => return,
PatKind::Path(ref path) if match_qpath(path, &paths::OPTION_NONE) => "is_none()",
_ => return,
};
// check that `while_let_on_iterator` lint does not trigger
@ -1547,7 +1531,6 @@ mod redundant_pattern_match {
if arms.len() == 2 {
let node_pair = (&arms[0].pat.kind, &arms[1].pat.kind);
let hir_id = expr.hir_id;
let found_good_method = match node_pair {
(
PatKind::TupleStruct(ref path_left, ref patterns_left, _),
@ -1562,8 +1545,6 @@ mod redundant_pattern_match {
&paths::RESULT_ERR,
"is_ok()",
"is_err()",
|| true,
|| true,
)
} else {
None
@ -1582,8 +1563,6 @@ mod redundant_pattern_match {
&paths::OPTION_NONE,
"is_some()",
"is_none()",
|| can_suggest(cx, hir_id, sym!(option_type), "is_some"),
|| can_suggest(cx, hir_id, sym!(option_type), "is_none"),
)
} else {
None
@ -1616,7 +1595,6 @@ mod redundant_pattern_match {
}
}
#[allow(clippy::too_many_arguments)]
fn find_good_method_for_match<'a>(
arms: &[Arm<'_>],
path_left: &QPath<'_>,
@ -1625,8 +1603,6 @@ mod redundant_pattern_match {
expected_right: &[&str],
should_be_left: &'a str,
should_be_right: &'a str,
can_suggest_left: impl Fn() -> bool,
can_suggest_right: impl Fn() -> bool,
) -> Option<&'a str> {
let body_node_pair = if match_qpath(path_left, expected_left) && match_qpath(path_right, expected_right) {
(&(*arms[0].body).kind, &(*arms[1].body).kind)
@ -1638,35 +1614,13 @@ mod redundant_pattern_match {
match body_node_pair {
(ExprKind::Lit(ref lit_left), ExprKind::Lit(ref lit_right)) => match (&lit_left.node, &lit_right.node) {
(LitKind::Bool(true), LitKind::Bool(false)) if can_suggest_left() => Some(should_be_left),
(LitKind::Bool(false), LitKind::Bool(true)) if can_suggest_right() => Some(should_be_right),
(LitKind::Bool(true), LitKind::Bool(false)) => Some(should_be_left),
(LitKind::Bool(false), LitKind::Bool(true)) => Some(should_be_right),
_ => None,
},
_ => None,
}
}
fn can_suggest(cx: &LateContext<'_>, hir_id: HirId, diag_item: Symbol, name: &str) -> bool {
if !in_constant(cx, hir_id) {
return true;
}
// Avoid suggesting calls to non-`const fn`s in const contexts, see #5697.
cx.tcx
.get_diagnostic_item(diag_item)
.and_then(|def_id| {
cx.tcx.inherent_impls(def_id).iter().find_map(|imp| {
cx.tcx
.associated_items(*imp)
.in_definition_order()
.find_map(|item| match item.kind {
ty::AssocKind::Fn if item.ident.name.as_str() == name => Some(item.def_id),
_ => None,
})
})
})
.map_or(false, |def_id| is_const_fn(cx.tcx, def_id))
}
}
#[test]

39
src/tools/clippy/tests/ui/redundant_pattern_matching.fixed
View File

@ -76,7 +76,6 @@ fn main() {
takes_bool(x);
issue5504();
issue5697();
issue6067();
let _ = if gen_opt().is_some() {
@ -129,41 +128,31 @@ fn issue5504() {
while m!().is_some() {}
}
// None of these should be linted because none of the suggested methods
// are `const fn` without toggling a feature.
const fn issue5697() {
if let Some(_) = Some(42) {}
if let None = None::<()> {}
while let Some(_) = Some(42) {}
while let None = None::<()> {}
match Some(42) {
Some(_) => true,
None => false,
};
match None::<()> {
Some(_) => false,
None => true,
};
}
// Methods that are unstable const should not be suggested within a const context, see issue #5697.
// However, in Rust 1.48.0 the methods `is_ok` and `is_err` of `Result` were stabilized as const,
// so the following should be linted.
// However, in Rust 1.48.0 the methods `is_ok` and `is_err` of `Result`, and `is_some` and `is_none`
// of `Option` were stabilized as const, so the following should be linted.
const fn issue6067() {
if Ok::<i32, i32>(42).is_ok() {}
if Err::<i32, i32>(42).is_err() {}
if Some(42).is_some() {}
if None::<()>.is_none() {}
while Ok::<i32, i32>(10).is_ok() {}
while Ok::<i32, i32>(10).is_err() {}
while Some(42).is_some() {}
while None::<()>.is_none() {}
Ok::<i32, i32>(42).is_ok();
Err::<i32, i32>(42).is_err();
Some(42).is_some();
None::<()>.is_none();
}

49
src/tools/clippy/tests/ui/redundant_pattern_matching.rs
View File

@ -97,7 +97,6 @@ fn main() {
takes_bool(x);
issue5504();
issue5697();
issue6067();
let _ = if let Some(_) = gen_opt() {
@ -150,17 +149,36 @@ fn issue5504() {
while let Some(_) = m!() {}
}
// None of these should be linted because none of the suggested methods
// are `const fn` without toggling a feature.
const fn issue5697() {
// Methods that are unstable const should not be suggested within a const context, see issue #5697.
// However, in Rust 1.48.0 the methods `is_ok` and `is_err` of `Result`, and `is_some` and `is_none`
// of `Option` were stabilized as const, so the following should be linted.
const fn issue6067() {
if let Ok(_) = Ok::<i32, i32>(42) {}
if let Err(_) = Err::<i32, i32>(42) {}
if let Some(_) = Some(42) {}
if let None = None::<()> {}
while let Ok(_) = Ok::<i32, i32>(10) {}
while let Err(_) = Ok::<i32, i32>(10) {}
while let Some(_) = Some(42) {}
while let None = None::<()> {}
match Ok::<i32, i32>(42) {
Ok(_) => true,
Err(_) => false,
};
match Err::<i32, i32>(42) {
Ok(_) => false,
Err(_) => true,
};
match Some(42) {
Some(_) => true,
None => false,
@ -171,26 +189,3 @@ const fn issue5697() {
None => true,
};
}
// Methods that are unstable const should not be suggested within a const context, see issue #5697.
// However, in Rust 1.48.0 the methods `is_ok` and `is_err` of `Result` were stabilized as const,
// so the following should be linted.
const fn issue6067() {
if let Ok(_) = Ok::<i32, i32>(42) {}
if let Err(_) = Err::<i32, i32>(42) {}
while let Ok(_) = Ok::<i32, i32>(10) {}
while let Err(_) = Ok::<i32, i32>(10) {}
match Ok::<i32, i32>(42) {
Ok(_) => true,
Err(_) => false,
};
match Err::<i32, i32>(42) {
Ok(_) => false,
Err(_) => true,
};
}

72
src/tools/clippy/tests/ui/redundant_pattern_matching.stderr
View File

@ -149,79 +149,103 @@ LL | let x = if let Some(_) = opt { true } else { false };
| -------^^^^^^^------ help: try this: `if opt.is_some()`
error: redundant pattern matching, consider using `is_some()`
--> $DIR/redundant_pattern_matching.rs:103:20
--> $DIR/redundant_pattern_matching.rs:102:20
|
LL | let _ = if let Some(_) = gen_opt() {
| -------^^^^^^^------------ help: try this: `if gen_opt().is_some()`
error: redundant pattern matching, consider using `is_none()`
--> $DIR/redundant_pattern_matching.rs:105:19
--> $DIR/redundant_pattern_matching.rs:104:19
|
LL | } else if let None = gen_opt() {
| -------^^^^------------ help: try this: `if gen_opt().is_none()`
error: redundant pattern matching, consider using `is_ok()`
--> $DIR/redundant_pattern_matching.rs:107:19
--> $DIR/redundant_pattern_matching.rs:106:19
|
LL | } else if let Ok(_) = gen_res() {
| -------^^^^^------------ help: try this: `if gen_res().is_ok()`
error: redundant pattern matching, consider using `is_err()`
--> $DIR/redundant_pattern_matching.rs:109:19
--> $DIR/redundant_pattern_matching.rs:108:19
|
LL | } else if let Err(_) = gen_res() {
| -------^^^^^^------------ help: try this: `if gen_res().is_err()`
error: redundant pattern matching, consider using `is_some()`
--> $DIR/redundant_pattern_matching.rs:142:19
--> $DIR/redundant_pattern_matching.rs:141:19
|
LL | while let Some(_) = r#try!(result_opt()) {}
| ----------^^^^^^^----------------------- help: try this: `while r#try!(result_opt()).is_some()`
error: redundant pattern matching, consider using `is_some()`
--> $DIR/redundant_pattern_matching.rs:143:16
--> $DIR/redundant_pattern_matching.rs:142:16
|
LL | if let Some(_) = r#try!(result_opt()) {}
| -------^^^^^^^----------------------- help: try this: `if r#try!(result_opt()).is_some()`
error: redundant pattern matching, consider using `is_some()`
--> $DIR/redundant_pattern_matching.rs:149:12
--> $DIR/redundant_pattern_matching.rs:148:12
|
LL | if let Some(_) = m!() {}
| -------^^^^^^^------- help: try this: `if m!().is_some()`
error: redundant pattern matching, consider using `is_some()`
--> $DIR/redundant_pattern_matching.rs:150:15
--> $DIR/redundant_pattern_matching.rs:149:15
|
LL | while let Some(_) = m!() {}
| ----------^^^^^^^------- help: try this: `while m!().is_some()`
error: redundant pattern matching, consider using `is_ok()`
--> $DIR/redundant_pattern_matching.rs:179:12
--> $DIR/redundant_pattern_matching.rs:156:12
|
LL | if let Ok(_) = Ok::<i32, i32>(42) {}
| -------^^^^^--------------------- help: try this: `if Ok::<i32, i32>(42).is_ok()`
error: redundant pattern matching, consider using `is_err()`
--> $DIR/redundant_pattern_matching.rs:181:12
--> $DIR/redundant_pattern_matching.rs:158:12
|
LL | if let Err(_) = Err::<i32, i32>(42) {}
| -------^^^^^^---------------------- help: try this: `if Err::<i32, i32>(42).is_err()`
error: redundant pattern matching, consider using `is_some()`
--> $DIR/redundant_pattern_matching.rs:160:12
|
LL | if let Some(_) = Some(42) {}
| -------^^^^^^^----------- help: try this: `if Some(42).is_some()`
error: redundant pattern matching, consider using `is_none()`
--> $DIR/redundant_pattern_matching.rs:162:12
|
LL | if let None = None::<()> {}
| -------^^^^------------- help: try this: `if None::<()>.is_none()`
error: redundant pattern matching, consider using `is_ok()`
--> $DIR/redundant_pattern_matching.rs:183:15
--> $DIR/redundant_pattern_matching.rs:164:15
|
LL | while let Ok(_) = Ok::<i32, i32>(10) {}
| ----------^^^^^--------------------- help: try this: `while Ok::<i32, i32>(10).is_ok()`
error: redundant pattern matching, consider using `is_err()`
--> $DIR/redundant_pattern_matching.rs:185:15
--> $DIR/redundant_pattern_matching.rs:166:15
|
LL | while let Err(_) = Ok::<i32, i32>(10) {}
| ----------^^^^^^--------------------- help: try this: `while Ok::<i32, i32>(10).is_err()`
error: redundant pattern matching, consider using `is_some()`
--> $DIR/redundant_pattern_matching.rs:168:15
|
LL | while let Some(_) = Some(42) {}
| ----------^^^^^^^----------- help: try this: `while Some(42).is_some()`
error: redundant pattern matching, consider using `is_none()`
--> $DIR/redundant_pattern_matching.rs:170:15
|
LL | while let None = None::<()> {}
| ----------^^^^------------- help: try this: `while None::<()>.is_none()`
error: redundant pattern matching, consider using `is_ok()`
--> $DIR/redundant_pattern_matching.rs:187:5
--> $DIR/redundant_pattern_matching.rs:172:5
|
LL | / match Ok::<i32, i32>(42) {
LL | | Ok(_) => true,
@ -230,7 +254,7 @@ LL | | };
| |_____^ help: try this: `Ok::<i32, i32>(42).is_ok()`
error: redundant pattern matching, consider using `is_err()`
--> $DIR/redundant_pattern_matching.rs:192:5
--> $DIR/redundant_pattern_matching.rs:177:5
|
LL | / match Err::<i32, i32>(42) {
LL | | Ok(_) => false,
@ -238,5 +262,23 @@ LL | | Err(_) => true,
LL | | };
| |_____^ help: try this: `Err::<i32, i32>(42).is_err()`
error: aborting due to 35 previous errors
error: redundant pattern matching, consider using `is_some()`
--> $DIR/redundant_pattern_matching.rs:182:5
|
LL | / match Some(42) {
LL | | Some(_) => true,
LL | | None => false,
LL | | };
| |_____^ help: try this: `Some(42).is_some()`
error: redundant pattern matching, consider using `is_none()`
--> $DIR/redundant_pattern_matching.rs:187:5
|
LL | / match None::<()> {
LL | | Some(_) => false,
LL | | None => true,
LL | | };
| |_____^ help: try this: `None::<()>.is_none()`
error: aborting due to 41 previous errors