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gate let_chains in all places before the 2024 edition #140198

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43 changes: 15 additions & 28 deletions compiler/rustc_parse/src/parser/expr.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2605,8 +2605,7 @@
let lo = self.prev_token.span;
// Scoping code checks the top level edition of the `if`; let's match it here.
// The `CondChecker` also checks the edition of the `let` itself, just to make sure.
let let_chains_policy = LetChainsPolicy::EditionDependent { current_edition: lo.edition() };
let cond = self.parse_expr_cond(let_chains_policy)?;
let cond = self.parse_expr_cond(lo.edition())?;
self.parse_if_after_cond(lo, cond)
}

Expand Down Expand Up @@ -2716,16 +2715,16 @@

/// Parses the condition of a `if` or `while` expression.
///
/// The specified `edition` in `let_chains_policy` should be that of the whole `if` construct,
/// i.e. the same span we use to later decide whether the drop behaviour should be that of
/// edition `..=2021` or that of `2024..`.
/// The specified `edition` should be that of the whole `if` construct, i.e. the same span
/// we use to later decide whether the drop behaviour should be that of edition `..=2021`
/// or that of `2024..`.
// Public because it is used in rustfmt forks such as https://github.com/tucant/rustfmt/blob/30c83df9e1db10007bdd16dafce8a86b404329b2/src/parse/macros/html.rs#L57 for custom if expressions.
pub fn parse_expr_cond(&mut self, let_chains_policy: LetChainsPolicy) -> PResult<'a, P<Expr>> {
pub fn parse_expr_cond(&mut self, edition: Edition) -> PResult<'a, P<Expr>> {
let attrs = self.parse_outer_attributes()?;
let (mut cond, _) =
self.parse_expr_res(Restrictions::NO_STRUCT_LITERAL | Restrictions::ALLOW_LET, attrs)?;

CondChecker::new(self, let_chains_policy).visit_expr(&mut cond);
CondChecker::new(self, edition).visit_expr(&mut cond);

Ok(cond)
}
Expand Down Expand Up @@ -3020,8 +3019,7 @@

/// Parses a `while` or `while let` expression (`while` token already eaten).
fn parse_expr_while(&mut self, opt_label: Option<Label>, lo: Span) -> PResult<'a, P<Expr>> {
let policy = LetChainsPolicy::EditionDependent { current_edition: lo.edition() };
let cond = self.parse_expr_cond(policy).map_err(|mut err| {
let cond = self.parse_expr_cond(lo.edition()).map_err(|mut err| {
err.span_label(lo, "while parsing the condition of this `while` expression");
err
})?;
Expand Down Expand Up @@ -3426,7 +3424,8 @@
let if_span = self.prev_token.span;
let mut cond = self.parse_match_guard_condition()?;

CondChecker::new(self, LetChainsPolicy::AlwaysAllowed).visit_expr(&mut cond);
// TODO explain

Check failure on line 3427 in compiler/rustc_parse/src/parser/expr.rs

View workflow job for this annotation

GitHub Actions / PR - mingw-check-tidy 

TODO is used for tasks that should be done before merging a PR; If you want to leave a message in the codebase use FIXME
CondChecker::new(self, if_span.edition()).visit_expr(&mut cond);

if has_let_expr(&cond) {
let span = if_span.to(cond.span);
Expand Down Expand Up @@ -3455,7 +3454,7 @@
unreachable!()
};
self.psess.gated_spans.ungate_last(sym::guard_patterns, cond.span);
CondChecker::new(self, LetChainsPolicy::AlwaysAllowed).visit_expr(&mut cond);
CondChecker::new(self, span.edition()).visit_expr(&mut cond);
let right = self.prev_token.span;
self.dcx().emit_err(errors::ParenthesesInMatchPat {
span: vec![left, right],
Expand Down Expand Up @@ -4026,13 +4025,6 @@
NotSupportedParentheses(#[primary_span] Span),
}

/// Whether let chains are allowed on all editions, or it's edition dependent (allowed only on
/// 2024 and later). In case of edition dependence, specify the currently present edition.
pub enum LetChainsPolicy {
AlwaysAllowed,
EditionDependent { current_edition: Edition },
}

/// Visitor to check for invalid use of `ExprKind::Let` that can't
/// easily be caught in parsing. For example:
///
Expand All @@ -4044,21 +4036,21 @@
/// ```
struct CondChecker<'a> {
parser: &'a Parser<'a>,
let_chains_policy: LetChainsPolicy,
current_edition: Edition,
depth: u32,
forbid_let_reason: Option<ForbiddenLetReason>,
missing_let: Option<errors::MaybeMissingLet>,
comparison: Option<errors::MaybeComparison>,
}

impl<'a> CondChecker<'a> {
fn new(parser: &'a Parser<'a>, let_chains_policy: LetChainsPolicy) -> Self {
fn new(parser: &'a Parser<'a>, current_edition: Edition) -> Self {
CondChecker {
parser,
forbid_let_reason: None,
missing_let: None,
comparison: None,
let_chains_policy,
current_edition,
depth: 0,
}
}
Expand All @@ -4083,13 +4075,8 @@
));
} else if self.depth > 1 {
// Top level `let` is always allowed; only gate chains
match self.let_chains_policy {
LetChainsPolicy::AlwaysAllowed => (),
LetChainsPolicy::EditionDependent { current_edition } => {
if !current_edition.at_least_rust_2024() || !span.at_least_rust_2024() {
self.parser.psess.gated_spans.gate(sym::let_chains, span);
}
}
if !self.current_edition.at_least_rust_2024() || !span.at_least_rust_2024() {
self.parser.psess.gated_spans.gate(sym::let_chains, span);
}
}
}
Expand Down
5 changes: 5 additions & 0 deletions tests/ui/rfcs/rfc-2294-if-let-guard/feature-gate.rs
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -15,9 +15,11 @@ fn _if_let_guard() {

() if true && let 0 = 1 => {}
//~^ ERROR `if let` guards are experimental
//~| ERROR `let` expressions in this position are unstable

() if let 0 = 1 && true => {}
//~^ ERROR `if let` guards are experimental
//~| ERROR `let` expressions in this position are unstable

() if (let 0 = 1) && true => {}
//~^ ERROR expected expression, found `let` statement
Expand All @@ -31,13 +33,16 @@ fn _if_let_guard() {

() if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
//~^ ERROR `if let` guards are experimental
//~| ERROR `let` expressions in this position are unstable
//~| ERROR `let` expressions in this position are unstable
//~| ERROR expected expression, found `let` statement
//~| ERROR expected expression, found `let` statement
//~| ERROR expected expression, found `let` statement


() if let Range { start: _, end: _ } = (true..true) && false => {}
//~^ ERROR `if let` guards are experimental
//~| ERROR `let` expressions in this position are unstable

_ => {}
}
Expand Down
100 changes: 75 additions & 25 deletions tests/ui/rfcs/rfc-2294-if-let-guard/feature-gate.stderr
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -25,106 +25,106 @@ LL | () if (((let 0 = 1))) => {}
| ^^^^^^^^^

error: expected expression, found `let` statement
--> $DIR/feature-gate.rs:22:16
--> $DIR/feature-gate.rs:24:16
|
LL | () if (let 0 = 1) && true => {}
| ^^^^^^^^^
|
= note: only supported directly in conditions of `if` and `while` expressions
note: `let`s wrapped in parentheses are not supported in a context with let chains
--> $DIR/feature-gate.rs:22:16
--> $DIR/feature-gate.rs:24:16
|
LL | () if (let 0 = 1) && true => {}
| ^^^^^^^^^

error: expected expression, found `let` statement
--> $DIR/feature-gate.rs:25:24
--> $DIR/feature-gate.rs:27:24
|
LL | () if true && (let 0 = 1) => {}
| ^^^^^^^^^
|
= note: only supported directly in conditions of `if` and `while` expressions
note: `let`s wrapped in parentheses are not supported in a context with let chains
--> $DIR/feature-gate.rs:25:24
--> $DIR/feature-gate.rs:27:24
|
LL | () if true && (let 0 = 1) => {}
| ^^^^^^^^^

error: expected expression, found `let` statement
--> $DIR/feature-gate.rs:28:16
--> $DIR/feature-gate.rs:30:16
|
LL | () if (let 0 = 1) && (let 0 = 1) => {}
| ^^^^^^^^^
|
= note: only supported directly in conditions of `if` and `while` expressions
note: `let`s wrapped in parentheses are not supported in a context with let chains
--> $DIR/feature-gate.rs:28:16
--> $DIR/feature-gate.rs:30:16
|
LL | () if (let 0 = 1) && (let 0 = 1) => {}
| ^^^^^^^^^

error: expected expression, found `let` statement
--> $DIR/feature-gate.rs:28:31
--> $DIR/feature-gate.rs:30:31
|
LL | () if (let 0 = 1) && (let 0 = 1) => {}
| ^^^^^^^^^
|
= note: only supported directly in conditions of `if` and `while` expressions
note: `let`s wrapped in parentheses are not supported in a context with let chains
--> $DIR/feature-gate.rs:28:31
--> $DIR/feature-gate.rs:30:31
|
LL | () if (let 0 = 1) && (let 0 = 1) => {}
| ^^^^^^^^^

error: expected expression, found `let` statement
--> $DIR/feature-gate.rs:32:42
--> $DIR/feature-gate.rs:34:42
|
LL | () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
| ^^^^^^^^^
|
= note: only supported directly in conditions of `if` and `while` expressions
note: `let`s wrapped in parentheses are not supported in a context with let chains
--> $DIR/feature-gate.rs:32:42
--> $DIR/feature-gate.rs:34:42
|
LL | () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: expected expression, found `let` statement
--> $DIR/feature-gate.rs:32:55
--> $DIR/feature-gate.rs:34:55
|
LL | () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
| ^^^^^^^^^
|
= note: only supported directly in conditions of `if` and `while` expressions
note: `let`s wrapped in parentheses are not supported in a context with let chains
--> $DIR/feature-gate.rs:32:42
--> $DIR/feature-gate.rs:34:42
|
LL | () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: expected expression, found `let` statement
--> $DIR/feature-gate.rs:32:68
--> $DIR/feature-gate.rs:34:68
|
LL | () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
| ^^^^^^^^^
|
= note: only supported directly in conditions of `if` and `while` expressions
note: `let`s wrapped in parentheses are not supported in a context with let chains
--> $DIR/feature-gate.rs:32:42
--> $DIR/feature-gate.rs:34:42
|
LL | () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error: expected expression, found `let` statement
--> $DIR/feature-gate.rs:55:16
--> $DIR/feature-gate.rs:60:16
|
LL | use_expr!((let 0 = 1 && 0 == 0));
| ^^^
|
= note: only supported directly in conditions of `if` and `while` expressions

error: expected expression, found `let` statement
--> $DIR/feature-gate.rs:55:16
--> $DIR/feature-gate.rs:60:16
|
LL | use_expr!((let 0 = 1 && 0 == 0));
| ^^^
Expand All @@ -133,15 +133,15 @@ LL | use_expr!((let 0 = 1 && 0 == 0));
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`

error: expected expression, found `let` statement
--> $DIR/feature-gate.rs:58:16
--> $DIR/feature-gate.rs:63:16
|
LL | use_expr!((let 0 = 1));
| ^^^
|
= note: only supported directly in conditions of `if` and `while` expressions

error: expected expression, found `let` statement
--> $DIR/feature-gate.rs:58:16
--> $DIR/feature-gate.rs:63:16
|
LL | use_expr!((let 0 = 1));
| ^^^
Expand All @@ -150,7 +150,7 @@ LL | use_expr!((let 0 = 1));
= note: duplicate diagnostic emitted due to `-Z deduplicate-diagnostics=no`

error: no rules expected keyword `let`
--> $DIR/feature-gate.rs:67:15
--> $DIR/feature-gate.rs:72:15
|
LL | macro_rules! use_expr {
| --------------------- when calling this macro
Expand All @@ -159,7 +159,7 @@ LL | use_expr!(let 0 = 1);
| ^^^ no rules expected this token in macro call
|
note: while trying to match meta-variable `$e:expr`
--> $DIR/feature-gate.rs:48:10
--> $DIR/feature-gate.rs:53:10
|
LL | ($e:expr) => {
| ^^^^^^^
Expand Down Expand Up @@ -187,7 +187,7 @@ LL | () if true && let 0 = 1 => {}
= help: you can write `if matches!(<expr>, <pattern>)` instead of `if let <pattern> = <expr>`

error[E0658]: `if let` guards are experimental
--> $DIR/feature-gate.rs:19:12
--> $DIR/feature-gate.rs:20:12
|
LL | () if let 0 = 1 && true => {}
| ^^^^^^^^^^^^^^^^^^^^
Expand All @@ -198,7 +198,7 @@ LL | () if let 0 = 1 && true => {}
= help: you can write `if matches!(<expr>, <pattern>)` instead of `if let <pattern> = <expr>`

error[E0658]: `if let` guards are experimental
--> $DIR/feature-gate.rs:32:12
--> $DIR/feature-gate.rs:34:12
|
LL | () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Expand All @@ -209,7 +209,7 @@ LL | () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 =
= help: you can write `if matches!(<expr>, <pattern>)` instead of `if let <pattern> = <expr>`

error[E0658]: `if let` guards are experimental
--> $DIR/feature-gate.rs:39:12
--> $DIR/feature-gate.rs:43:12
|
LL | () if let Range { start: _, end: _ } = (true..true) && false => {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Expand All @@ -220,7 +220,7 @@ LL | () if let Range { start: _, end: _ } = (true..true) && false => {}
= help: you can write `if matches!(<expr>, <pattern>)` instead of `if let <pattern> = <expr>`

error[E0658]: `if let` guards are experimental
--> $DIR/feature-gate.rs:63:12
--> $DIR/feature-gate.rs:68:12
|
LL | () if let 0 = 1 => {}
| ^^^^^^^^^^^^
Expand All @@ -230,6 +230,56 @@ LL | () if let 0 = 1 => {}
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date
= help: you can write `if matches!(<expr>, <pattern>)` instead of `if let <pattern> = <expr>`

error: aborting due to 20 previous errors
error[E0658]: `let` expressions in this position are unstable
--> $DIR/feature-gate.rs:16:23
|
LL | () if true && let 0 = 1 => {}
| ^^^^^^^^^
|
= note: see issue #53667 <https://github.com/rust-lang/rust/issues/53667> for more information
= help: add `#![feature(let_chains)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error[E0658]: `let` expressions in this position are unstable
--> $DIR/feature-gate.rs:20:15
|
LL | () if let 0 = 1 && true => {}
| ^^^^^^^^^
|
= note: see issue #53667 <https://github.com/rust-lang/rust/issues/53667> for more information
= help: add `#![feature(let_chains)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error[E0658]: `let` expressions in this position are unstable
--> $DIR/feature-gate.rs:34:15
|
LL | () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
| ^^^^^^^^^
|
= note: see issue #53667 <https://github.com/rust-lang/rust/issues/53667> for more information
= help: add `#![feature(let_chains)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error[E0658]: `let` expressions in this position are unstable
--> $DIR/feature-gate.rs:34:28
|
LL | () if let 0 = 1 && let 1 = 2 && (let 2 = 3 && let 3 = 4 && let 4 = 5) => {}
| ^^^^^^^^^
|
= note: see issue #53667 <https://github.com/rust-lang/rust/issues/53667> for more information
= help: add `#![feature(let_chains)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error[E0658]: `let` expressions in this position are unstable
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Is this fine in the 2024 edition? If so it should say that rather than it being unstable.

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It's due to the way #132833 was done: it just exempted 2024 usages from the feature gate instead of stabilizing the feature gate and adding an edition dependent error. I left that for future work, as I didn't know when it would stabilize. Plus, I saw that a lot of compiler crates were using let chains and I didn't want to play catch up with all the #![feature(let_chains)] changes happening that occur as the compiler does changes naturally (knowing that the stabilization would likely take months).

--> $DIR/feature-gate.rs:43:15
|
LL | () if let Range { start: _, end: _ } = (true..true) && false => {}
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: see issue #53667 <https://github.com/rust-lang/rust/issues/53667> for more information
= help: add `#![feature(let_chains)]` to the crate attributes to enable
= note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error: aborting due to 25 previous errors

For more information about this error, try `rustc --explain E0658`.
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