Stabilize allow irrefutable if-let patterns

src/librustc/lint/builtin.rs

@@ -290,7 +290,7 @@ declare_lint! {
 
 declare_lint! {
  pub IRREFUTABLE_LET_PATTERNS,
- Deny,
+ Warn,
  "detects irrefutable patterns in if-let and while-let statements"
 }
 

src/librustc_mir/diagnostics.rs

@@ -335,11 +335,13 @@ 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);
 
@@ -362,11 +364,13 @@ 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);
 

src/librustc_mir/hair/pattern/check_match.rs

@@ -364,7 +364,7 @@ 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 = vec![pat];
@@ -373,27 +373,10 @@ 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 => {
@@ -408,21 +391,10 @@ 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!(),
  }

src/libsyntax/feature_gate.rs

@@ -428,9 +428,6 @@ 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),
 
@@ -686,6 +683,9 @@ declare_features! (
  (accepted, extern_crate_item_prelude, "1.31.0", Some(55599), None),
  // Allows use of the `:literal` macro fragment specifier (RFC 1576).
  (accepted, macro_literal_matcher, "1.31.0", Some(35625), None),
+ // Allows irrefutable patterns in if-let and while-let statements (RFC 2086)
+ (accepted, irrefutable_let_patterns, "1.32.0", Some(44495), None),
+ // Use `?` as the Kleene "at most one" operator
  // Integer match exhaustiveness checking (RFC 2591)
  (accepted, exhaustive_integer_patterns, "1.32.0", Some(50907), None),
  // Use `?` as the Kleene "at most one" operator.

src/test/ui/feature-gates/feature-gate-without_gate_irrefutable_pattern.rs → src/test/run-pass/allow-irrefutable-if-let.rs

@@ -1,6 +1,4 @@
-// gate-test-irrefutable_let_patterns
-
-// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //
@@ -12,6 +10,7 @@
 
 #[allow(irrefutable_let_patterns)]
 fn main() {
- if let _ = 5 {}
- //~^ ERROR 15:12: 15:13: irrefutable if-let pattern [E0162]
+ if let _ = 5 {
+ let _x = 1;
+ }
 }

src/test/ui/should-fail-no_gate_irrefutable_if_let_pattern.rs → src/test/run-pass/allow-irrefutable-while-let.rs

@@ -1,4 +1,4 @@
-// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
 // file at the top-level directory of this distribution and at
 // http://rust-lang.org/COPYRIGHT.
 //
@@ -8,8 +8,9 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// should-fail-irrefutable_let_patterns
+#[allow(irrefutable_let_patterns)]
 fn main() {
- if let _ = 5 {}
- //~^ ERROR irrefutable if-let pattern [E0162]
+ while let _ = 5 {
+ break;
+ }
 }

src/test/run-pass/binding/allow_irrefutable_let_patterns.stderr

@@ -0,0 +1,8 @@
+warning: the feature `irrefutable_let_patterns` has been stable since 1.32.0 and no longer requires an attribute to enable
+
+ --> $DIR/allow_irrefutable_let_patterns.rs:12:12
+ |
+LL | #![feature(irrefutable_let_patterns)]
+ | ^^^^^^^^^^^^^^^^^^^^^^^^
+ |
+ = note: #[warn(stable_features)] on by default

src/test/ui/if/if-let.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+// compile-pass
+
 fn macros() {
  macro_rules! foo{
  ($p:pat, $e:expr, $b:block) => {{
@@ -20,20 +22,20 @@ fn macros() {
  }}
  }
 
- foo!(a, 1, { //~ ERROR irrefutable if-let
+ foo!(a, 1, { //~ warning irrefutable if-let
  println!("irrefutable pattern");
  });
- bar!(a, 1, { //~ ERROR irrefutable if-let
+ bar!(a, 1, { //~ warning irrefutable if-let
  println!("irrefutable pattern");
  });
 }
 
 pub fn main() {
- if let a = 1 { //~ ERROR irrefutable if-let
+ if let a = 1 { //~ warning irrefutable if-let
  println!("irrefutable pattern");
  }
 
- if let a = 1 { //~ ERROR irrefutable if-let
+ if let a = 1 { //~ warning irrefutable if-let
  println!("irrefutable pattern");
  } else if true {
  println!("else-if in irrefutable if-let");
@@ -43,13 +45,13 @@ pub fn main() {
 
  if let 1 = 2 {
  println!("refutable pattern");
- } else if let a = 1 { //~ ERROR irrefutable if-let
+ } else if let a = 1 { //~ warning irrefutable if-let
  println!("irrefutable pattern");
  }
 
  if true {
  println!("if");
- } else if let a = 1 { //~ ERROR irrefutable if-let
+ } else if let a = 1 { //~ warning irrefutable if-let
  println!("irrefutable pattern");
  }
 }

src/test/ui/if/if-let.stderr

@@ -1,39 +1,62 @@
-error[E0162]: irrefutable if-let pattern
- --> $DIR/if-let.rs:23:10
+warning: irrefutable if-let pattern
+ --> $DIR/if-let.rs:16:13
  |
-LL | foo!(a, 1, { //~ ERROR irrefutable if-let
- | ^ irrefutable pattern
-
-error[E0162]: irrefutable if-let pattern
- --> $DIR/if-let.rs:26:10
+LL | if let $p = $e $b
+ | ^^
+...
+LL | / foo!(a, 1, { //~ warning 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:32:12
+warning: irrefutable if-let pattern
+ --> $DIR/if-let.rs:16:13
  |
-LL | if let a = 1 { //~ ERROR irrefutable if-let
- | ^ irrefutable pattern
+LL | if let $p = $e $b
+ | ^^
+...
+LL | / bar!(a, 1, { //~ warning irrefutable if-let
+LL | | println!("irrefutable pattern");
+LL | | });
+ | |_______- in this macro invocation
 
-error[E0162]: irrefutable if-let pattern
- --> $DIR/if-let.rs:36:12
+warning: irrefutable if-let pattern
+ --> $DIR/if-let.rs:34:5
  |
-LL | if let a = 1 { //~ ERROR irrefutable if-let
- | ^ irrefutable pattern
+LL | / if let a = 1 { //~ warning irrefutable if-let
+LL | | println!("irrefutable pattern");
+LL | | }
+ | |_____^
 
-error[E0162]: irrefutable if-let pattern
- --> $DIR/if-let.rs:46:19
+warning: irrefutable if-let pattern
+ --> $DIR/if-let.rs:38:5
  |
-LL | } else if let a = 1 { //~ ERROR irrefutable if-let
- | ^ irrefutable pattern
+LL | / if let a = 1 { //~ warning 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:52:19
+warning: irrefutable if-let pattern
+ --> $DIR/if-let.rs:48:12
  |
-LL | } else if let a = 1 { //~ ERROR irrefutable if-let
- | ^ irrefutable pattern
+LL | } else if let a = 1 { //~ warning irrefutable if-let
+ | ____________^
+LL | | println!("irrefutable pattern");
+LL | | }
+ | |_____^
 
-error: aborting due to 6 previous errors
+warning: irrefutable if-let pattern
+ --> $DIR/if-let.rs:54:12
+ |
+LL | } else if let a = 1 { //~ warning irrefutable if-let
+ | ____________^
+LL | | println!("irrefutable pattern");
+LL | | }
+ | |_____^
 
-For more information about this error, try `rustc --explain E0162`.

src/test/ui/issues/issue-51714.rs

@@ -20,5 +20,5 @@ fn main() {
 
  [(); return while let Some(n) = Some(0) {}];
  //~^ ERROR return statement outside of function body
- //~^^ ERROR irrefutable while-let pattern
+ //~^^ warning irrefutable while-let pattern
 }