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Stabilise irrefutable if-let and while-let patterns #57535

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merged 2 commits into from Jan 12, 2019
Merged

Stabilise irrefutable if-let and while-let patterns #57535

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afcb938
Stabilise irrefutable if-let and while-let patterns
varkor Jan 12, 2019
0e1402d
bless ui/while-let
Centril Jan 12, 2019
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28 changes: 0 additions & 28 deletions src/doc/unstable-book/src/language-features/irrefutable-let-patterns.md
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2 changes: 1 addition & 1 deletion src/librustc/lint/builtin.rs
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Expand Up @@ -286,7 +286,7 @@ declare_lint! {

declare_lint! {
pub IRREFUTABLE_LET_PATTERNS,
Deny,
Warn,
"detects irrefutable patterns in if-let and while-let statements"
}

Expand Down
8 changes: 6 additions & 2 deletions src/librustc_mir/diagnostics.rs
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Expand Up @@ -325,11 +325,13 @@ match Some(42) {
"##,

E0162: r##"
#### Note: this error code is no longer emitted by the compiler.

An if-let pattern attempts to match the pattern, and enters the body if the
match was successful. If the match is irrefutable (when it cannot fail to
match), use a regular `let`-binding instead. For instance:

```compile_fail,E0162
```compile_pass
struct Irrefutable(i32);
let irr = Irrefutable(0);

Expand All @@ -352,11 +354,13 @@ println!("{}", x);
"##,

E0165: r##"
#### Note: this error code is no longer emitted by the compiler.

A while-let pattern attempts to match the pattern, and enters the body if the
match was successful. If the match is irrefutable (when it cannot fail to
match), use a regular `let`-binding inside a `loop` instead. For instance:

```compile_fail,E0165
```compile_pass,no_run
struct Irrefutable(i32);
let irr = Irrefutable(0);

Expand Down
49 changes: 12 additions & 37 deletions src/librustc_mir/hair/pattern/check_match.rs
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Expand Up @@ -350,7 +350,6 @@ fn check_arms<'a, 'tcx>(cx: &mut MatchCheckCtxt<'a, 'tcx>,
{
let mut seen = Matrix::empty();
let mut catchall = None;
let mut printed_if_let_err = false;
for (arm_index, &(ref pats, guard)) in arms.iter().enumerate() {
for &(pat, hir_pat) in pats {
let v = smallvec![pat];
Expand All @@ -359,27 +358,12 @@ fn check_arms<'a, 'tcx>(cx: &mut MatchCheckCtxt<'a, 'tcx>,
NotUseful => {
match source {
hir::MatchSource::IfLetDesugar { .. } => {
if cx.tcx.features().irrefutable_let_patterns {
cx.tcx.lint_node(
lint::builtin::IRREFUTABLE_LET_PATTERNS,
hir_pat.id, pat.span,
"irrefutable if-let pattern");
} else {
if printed_if_let_err {
// we already printed an irrefutable if-let pattern error.
// We don't want two, that's just confusing.
} else {
// find the first arm pattern so we can use its span
let &(ref first_arm_pats, _) = &arms[0];
let first_pat = &first_arm_pats[0];
let span = first_pat.0.span;
struct_span_err!(cx.tcx.sess, span, E0162,
"irrefutable if-let pattern")
.span_label(span, "irrefutable pattern")
.emit();
printed_if_let_err = true;
}
}
cx.tcx.lint_node(
lint::builtin::IRREFUTABLE_LET_PATTERNS,
hir_pat.id,
pat.span,
"irrefutable if-let pattern",
);
}

hir::MatchSource::WhileLetDesugar => {
Expand All @@ -394,21 +378,12 @@ fn check_arms<'a, 'tcx>(cx: &mut MatchCheckCtxt<'a, 'tcx>,
},
// The arm with the wildcard pattern.
1 => {
if cx.tcx.features().irrefutable_let_patterns {
cx.tcx.lint_node(
lint::builtin::IRREFUTABLE_LET_PATTERNS,
hir_pat.id, pat.span,
"irrefutable while-let pattern");
} else {
// find the first arm pattern so we can use its span
let &(ref first_arm_pats, _) = &arms[0];
let first_pat = &first_arm_pats[0];
let span = first_pat.0.span;
struct_span_err!(cx.tcx.sess, span, E0165,
"irrefutable while-let pattern")
.span_label(span, "irrefutable pattern")
.emit();
}
cx.tcx.lint_node(
lint::builtin::IRREFUTABLE_LET_PATTERNS,
hir_pat.id,
pat.span,
"irrefutable while-let pattern",
);
},
_ => bug!(),
}
Expand Down
5 changes: 2 additions & 3 deletions src/libsyntax/feature_gate.rs
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Expand Up @@ -414,9 +414,6 @@ declare_features! (
// `#[doc(alias = "...")]`
(active, doc_alias, "1.27.0", Some(50146), None),

// Allows irrefutable patterns in `if let` and `while let` statements (RFC 2086).
(active, irrefutable_let_patterns, "1.27.0", Some(44495), None),

// inconsistent bounds in where clauses
(active, trivial_bounds, "1.28.0", Some(48214), None),

Expand Down Expand Up @@ -684,6 +681,8 @@ declare_features! (
(accepted, underscore_imports, "1.33.0", Some(48216), None),
// Allows `#[repr(packed(N))]` attribute on structs.
(accepted, repr_packed, "1.33.0", Some(33158), None),
// Allows irrefutable patterns in `if let` and `while let` statements (RFC 2086).
(accepted, irrefutable_let_patterns, "1.33.0", Some(44495), None),
// Allows calling `const unsafe fn` inside `unsafe` blocks in `const fn` functions.
(accepted, min_const_unsafe_fn, "1.33.0", Some(55607), None),
// `#[cfg_attr(predicate, multiple, attributes, here)]`
Expand Down
12 changes: 0 additions & 12 deletions src/test/run-pass/binding/allow_irrefutable_let_patterns.rs
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8 changes: 0 additions & 8 deletions src/test/ui/error-codes/E0162.rs
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9 changes: 0 additions & 9 deletions src/test/ui/error-codes/E0162.stderr
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9 changes: 0 additions & 9 deletions src/test/ui/error-codes/E0165.rs
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9 changes: 0 additions & 9 deletions src/test/ui/error-codes/E0165.stderr
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8 changes: 0 additions & 8 deletions src/test/ui/feature-gates/feature-gate-without_gate_irrefutable_pattern.rs
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9 changes: 0 additions & 9 deletions src/test/ui/feature-gates/feature-gate-without_gate_irrefutable_pattern.stderr
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14 changes: 8 additions & 6 deletions src/test/ui/if/if-let.rs
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@@ -1,3 +1,5 @@
// compile-pass

fn macros() {
macro_rules! foo{
($p:pat, $e:expr, $b:block) => {{
Expand All @@ -10,20 +12,20 @@ fn macros() {
}}
}

foo!(a, 1, { //~ ERROR irrefutable if-let
foo!(a, 1, { //~ WARN irrefutable if-let
println!("irrefutable pattern");
});
bar!(a, 1, { //~ ERROR irrefutable if-let
bar!(a, 1, { //~ WARN irrefutable if-let
println!("irrefutable pattern");
});
}

pub fn main() {
if let a = 1 { //~ ERROR irrefutable if-let
if let a = 1 { //~ WARN irrefutable if-let
println!("irrefutable pattern");
}

if let a = 1 { //~ ERROR irrefutable if-let
if let a = 1 { //~ WARN irrefutable if-let
println!("irrefutable pattern");
} else if true {
println!("else-if in irrefutable if-let");
Expand All @@ -33,13 +35,13 @@ pub fn main() {

if let 1 = 2 {
println!("refutable pattern");
} else if let a = 1 { //~ ERROR irrefutable if-let
} else if let a = 1 { //~ WARN irrefutable if-let
println!("irrefutable pattern");
}

if true {
println!("if");
} else if let a = 1 { //~ ERROR irrefutable if-let
} else if let a = 1 { //~ WARN irrefutable if-let
println!("irrefutable pattern");
}
}
77 changes: 50 additions & 27 deletions src/test/ui/if/if-let.stderr
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@@ -1,39 +1,62 @@
error[E0162]: irrefutable if-let pattern
--> $DIR/if-let.rs:13:10
warning: irrefutable if-let pattern
--> $DIR/if-let.rs:6:13
|
LL | foo!(a, 1, { //~ ERROR irrefutable if-let
| ^ irrefutable pattern

error[E0162]: irrefutable if-let pattern
--> $DIR/if-let.rs:16:10
LL | if let $p = $e $b
| ^^
...
LL | / foo!(a, 1, { //~ WARN irrefutable if-let
LL | | println!("irrefutable pattern");
LL | | });
| |_______- in this macro invocation
|
LL | bar!(a, 1, { //~ ERROR irrefutable if-let
| ^ irrefutable pattern
= note: #[warn(irrefutable_let_patterns)] on by default

error[E0162]: irrefutable if-let pattern
--> $DIR/if-let.rs:22:12
warning: irrefutable if-let pattern
--> $DIR/if-let.rs:6:13
|
LL | if let a = 1 { //~ ERROR irrefutable if-let
| ^ irrefutable pattern
LL | if let $p = $e $b
| ^^
...
LL | / bar!(a, 1, { //~ WARN irrefutable if-let
LL | | println!("irrefutable pattern");
LL | | });
| |_______- in this macro invocation

error[E0162]: irrefutable if-let pattern
--> $DIR/if-let.rs:26:12
warning: irrefutable if-let pattern
--> $DIR/if-let.rs:24:5
|
LL | if let a = 1 { //~ ERROR irrefutable if-let
| ^ irrefutable pattern
LL | / if let a = 1 { //~ WARN irrefutable if-let
LL | | println!("irrefutable pattern");
LL | | }
| |_____^

error[E0162]: irrefutable if-let pattern
--> $DIR/if-let.rs:36:19
warning: irrefutable if-let pattern
--> $DIR/if-let.rs:28:5
|
LL | } else if let a = 1 { //~ ERROR irrefutable if-let
| ^ irrefutable pattern
LL | / if let a = 1 { //~ WARN irrefutable if-let
LL | | println!("irrefutable pattern");
LL | | } else if true {
LL | | println!("else-if in irrefutable if-let");
LL | | } else {
LL | | println!("else in irrefutable if-let");
LL | | }
| |_____^

error[E0162]: irrefutable if-let pattern
--> $DIR/if-let.rs:42:19
warning: irrefutable if-let pattern
--> $DIR/if-let.rs:38:12
|
LL | } else if let a = 1 { //~ ERROR irrefutable if-let
| ^ irrefutable pattern
LL | } else if let a = 1 { //~ WARN irrefutable if-let
| ____________^
LL | | println!("irrefutable pattern");
LL | | }
| |_____^

error: aborting due to 6 previous errors
warning: irrefutable if-let pattern
--> $DIR/if-let.rs:44:12
|
LL | } else if let a = 1 { //~ WARN irrefutable if-let
| ____________^
LL | | println!("irrefutable pattern");
LL | | }
| |_____^

For more information about this error, try `rustc --explain E0162`.
2 changes: 1 addition & 1 deletion src/test/ui/issues/issue-51714.rs
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Expand Up @@ -10,5 +10,5 @@ fn main() {

[(); return while let Some(n) = Some(0) {}];
//~^ ERROR return statement outside of function body
//~^^ ERROR irrefutable while-let pattern
//~^^ WARN irrefutable while-let pattern
}
13 changes: 7 additions & 6 deletions src/test/ui/issues/issue-51714.stderr
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Expand Up @@ -22,13 +22,14 @@ error[E0572]: return statement outside of function body
LL | [(); return while let Some(n) = Some(0) {}];
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

error[E0165]: irrefutable while-let pattern
--> $DIR/issue-51714.rs:11:27
warning: irrefutable while-let pattern
--> $DIR/issue-51714.rs:11:17
|
LL | [(); return while let Some(n) = Some(0) {}];
| ^^^^^^^ irrefutable pattern
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
|
= note: #[warn(irrefutable_let_patterns)] on by default

error: aborting due to 5 previous errors
error: aborting due to 4 previous errors

Some errors occurred: E0165, E0572.
For more information about an error, try `rustc --explain E0165`.
For more information about this error, try `rustc --explain E0572`.