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Rollup merge of rust-lang#76135 - CDirkx:const-option, r=dtolnay,oli-obk
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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: rust-lang#67441).
I believe these methods to be eligible for stabilization because of the stabilization of rust-lang#49146 (Allow if and match in constants) and the trivial implementations, see also:  [PR#75463](rust-lang#75463).

Related: rust-lang#76225
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RalfJung authored Sep 21, 2020
2 parents a409a23 + 43cba34 commit c3abb82
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Showing 7 changed files with 126 additions and 144 deletions.
6 changes: 3 additions & 3 deletions library/core/src/option.rs
Original file line number Diff line number Diff line change
Expand Up @@ -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(_))
Expand All @@ -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()
Expand Down Expand Up @@ -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 {
Expand Down
16 changes: 16 additions & 0 deletions library/core/tests/option.rs
Original file line number Diff line number Diff line change
Expand Up @@ -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 changes: 0 additions & 14 deletions src/test/ui/consts/const-option.rs

This file was deleted.

78 changes: 16 additions & 62 deletions src/tools/clippy/clippy_lints/src/matches.rs
Original file line number Diff line number Diff line change
Expand Up @@ -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 {
Expand All @@ -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
Expand Down Expand Up @@ -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, _),
Expand All @@ -1562,8 +1545,6 @@ mod redundant_pattern_match {
&paths::RESULT_ERR,
"is_ok()",
"is_err()",
|| true,
|| true,
)
} else {
None
Expand All @@ -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
Expand Down Expand Up @@ -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<'_>,
Expand All @@ -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)
Expand All @@ -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]
Expand Down
39 changes: 14 additions & 25 deletions src/tools/clippy/tests/ui/redundant_pattern_matching.fixed
Original file line number Diff line number Diff line change
Expand Up @@ -76,7 +76,6 @@ fn main() {
takes_bool(x);

issue5504();
issue5697();
issue6067();

let _ = if gen_opt().is_some() {
Expand Down Expand Up @@ -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();
}
45 changes: 20 additions & 25 deletions src/tools/clippy/tests/ui/redundant_pattern_matching.rs
Original file line number Diff line number Diff line change
Expand Up @@ -97,7 +97,6 @@ fn main() {
takes_bool(x);

issue5504();
issue5697();
issue6067();

let _ = if let Some(_) = gen_opt() {
Expand Down Expand Up @@ -150,40 +149,26 @@ 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() {
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 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,
Expand All @@ -193,4 +178,14 @@ const fn issue6067() {
Ok(_) => false,
Err(_) => true,
};

match Some(42) {
Some(_) => true,
None => false,
};

match None::<()> {
Some(_) => false,
None => true,
};
}
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