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
 }