clean-up single_match a bit

Author: ada4a

clippy_lints/src/matches/single_match.rs

@@ -24,17 +24,16 @@ use super::{MATCH_BOOL, SINGLE_MATCH, SINGLE_MATCH_ELSE};
 /// span, e.g. a string literal `"//"`, but we know that this isn't the case for empty
 /// match arms.
 fn empty_arm_has_comment(cx: &LateContext<'_>, span: Span) -> bool {
-    if let Some(ff) = span.get_source_range(cx)
-        && let Some(text) = ff.as_str()
-    {
-        text.as_bytes().windows(2).any(|w| w == b"//" || w == b"/*")
-    } else {
-        false
-    }
+    span.check_source_text(cx, |text| text.as_bytes().windows(2).any(|w| w == b"//" || w == b"/*"))
 }
 
-#[rustfmt::skip]
-pub(crate) fn check<'tcx>(cx: &LateContext<'tcx>, ex: &'tcx Expr<'_>, arms: &'tcx [Arm<'_>], expr: &'tcx Expr<'_>, contains_comments: bool) {
+pub(crate) fn check<'tcx>(
+    cx: &LateContext<'tcx>,
+    ex: &'tcx Expr<'_>,
+    arms: &'tcx [Arm<'_>],
+    expr: &'tcx Expr<'_>,
+    contains_comments: bool,
+) {
     if let [arm1, arm2] = arms
         && !arms.iter().any(|arm| arm.guard.is_some() || arm.pat.span.from_expansion())
         && !expr.span.from_expansion()
@@ -226,13 +225,13 @@ enum PatState<'a> {
     Wild,
     /// A std enum we know won't be extended. Tracks the states of each variant separately.
     ///
-    /// This is not used for `Option` since it uses the current pattern to track it's state.
+    /// This is not used for `Option` since it uses the current pattern to track its state.
     StdEnum(&'a mut [PatState<'a>]),
     /// Either the initial state for a pattern or a non-std enum. There is currently no need to
     /// distinguish these cases.
     ///
     /// For non-std enums there's no need to track the state of sub-patterns as the state of just
-    /// this pattern on it's own is enough for linting. Consider two cases:
+    /// this pattern on its own is enough for linting. Consider two cases:
     /// * This enum has no wild match. This case alone is enough to determine we can lint.
     /// * This enum has a wild match and therefore all sub-patterns also have a wild match.
     ///
@@ -380,7 +379,11 @@ impl<'a> PatState<'a> {
                 self.add_pat(cx, pat)
             },
             PatKind::Tuple([sub_pat], pos)
-                if pos.as_opt_usize().is_none() || cx.typeck.pat_ty(pat).tuple_fields().len() == 1 =>
+                // `pat` looks like `(sub_pat)`, without a `..` -- has only one sub-pattern
+                if pos.as_opt_usize().is_none()
+                    // `pat` looks like `(sub_pat, ..)` or `(.., sub_pat)`, but its type is a unary tuple,
+                    // so it still only has one sub-pattern
+                    || cx.typeck.pat_ty(pat).tuple_fields().len() == 1 =>
             {
                 self.add_pat(cx, sub_pat)
             },

tests/ui/single_match.fixed

@@ -218,7 +218,7 @@ fn main() {
     };
 }
 
-fn issue_10808(bar: Option<i32>) {
+fn issue10808(bar: Option<i32>) {
     if let Some(v) = bar { unsafe {
         let r = &v as *const i32;
         println!("{}", *r);
@@ -330,6 +330,7 @@ pub struct Data([u8; 4]);
 const DATA: Data = Data([1, 2, 3, 4]);
 const CONST_I32: i32 = 1;
 
+// https://github.com/rust-lang/rust-clippy/issues/13012
 fn irrefutable_match() {
     println!();
     //~^^^^ single_match
@@ -367,7 +368,7 @@ fn irrefutable_match() {
     //~| NOTE: you might want to preserve the comments from inside the `match`
 }
 
-fn issue_14493() {
+fn issue14493() {
     macro_rules! mac {
         (some) => {
             Some(42)

tests/ui/single_match.rs

@@ -269,7 +269,7 @@ fn main() {
     };
 }
 
-fn issue_10808(bar: Option<i32>) {
+fn issue10808(bar: Option<i32>) {
     match bar {
         Some(v) => unsafe {
             let r = &v as *const i32;
@@ -397,6 +397,7 @@ pub struct Data([u8; 4]);
 const DATA: Data = Data([1, 2, 3, 4]);
 const CONST_I32: i32 = 1;
 
+// https://github.com/rust-lang/rust-clippy/issues/13012
 fn irrefutable_match() {
     match DATA {
         DATA => println!(),
@@ -462,7 +463,7 @@ fn irrefutable_match() {
     //~| NOTE: you might want to preserve the comments from inside the `match`
 }
 
-fn issue_14493() {
+fn issue14493() {
     macro_rules! mac {
         (some) => {
             Some(42)

tests/ui/single_match.stderr

@@ -225,7 +225,7 @@ LL | |     }
    | |_____^ help: try: `if &s[0..3] == b"foo" { println!() }`
 
 error: this pattern is irrefutable, `match` is useless
-  --> tests/ui/single_match.rs:401:5
+  --> tests/ui/single_match.rs:402:5
    |
 LL | /     match DATA {
 LL | |         DATA => println!(),
@@ -234,7 +234,7 @@ LL | |     }
    | |_____^ help: try: `println!();`
 
 error: this pattern is irrefutable, `match` is useless
-  --> tests/ui/single_match.rs:407:5
+  --> tests/ui/single_match.rs:408:5
    |
 LL | /     match CONST_I32 {
 LL | |         CONST_I32 => println!(),
@@ -243,7 +243,7 @@ LL | |     }
    | |_____^ help: try: `println!();`
 
 error: this pattern is irrefutable, `match` is useless
-  --> tests/ui/single_match.rs:414:5
+  --> tests/ui/single_match.rs:415:5
    |
 LL | /     match i {
 LL | |         i => {
@@ -263,7 +263,7 @@ LL +     }
    |
 
 error: this pattern is irrefutable, `match` is useless
-  --> tests/ui/single_match.rs:423:5
+  --> tests/ui/single_match.rs:424:5
    |
 LL | /     match i {
 LL | |         i => {},
@@ -272,7 +272,7 @@ LL | |     }
    | |_____^ help: `match` expression can be removed
 
 error: this pattern is irrefutable, `match` is useless
-  --> tests/ui/single_match.rs:429:5
+  --> tests/ui/single_match.rs:430:5
    |
 LL | /     match i {
 LL | |         i => (),
@@ -281,7 +281,7 @@ LL | |     }
    | |_____^ help: `match` expression can be removed
 
 error: this pattern is irrefutable, `match` is useless
-  --> tests/ui/single_match.rs:435:5
+  --> tests/ui/single_match.rs:436:5
    |
 LL | /     match CONST_I32 {
 LL | |         CONST_I32 => println!(),
@@ -290,7 +290,7 @@ LL | |     }
    | |_____^ help: try: `println!();`
 
 error: you seem to be trying to use `match` for destructuring a single pattern. Consider using `if let`
-  --> tests/ui/single_match.rs:443:5
+  --> tests/ui/single_match.rs:444:5
    |
 LL | /     match x.pop() {
 LL | |         // bla
@@ -302,7 +302,7 @@ LL | |     }
    = note: you might want to preserve the comments from inside the `match`
 
 error: you seem to be trying to use `match` for destructuring a single pattern. Consider using `if let`
-  --> tests/ui/single_match.rs:452:5
+  --> tests/ui/single_match.rs:453:5
    |
 LL | /     match x.pop() {
 LL | |         // bla
@@ -322,7 +322,7 @@ LL +     }
    |
 
 error: you seem to be trying to use `match` for destructuring a single pattern. Consider using `if let`
-  --> tests/ui/single_match.rs:478:5
+  --> tests/ui/single_match.rs:479:5
    |
 LL | /     match mac!(some) {
 LL | |         Some(u) => println!("{u}"),
@@ -331,7 +331,7 @@ LL | |     }
    | |_____^ help: try: `if let Some(u) = mac!(some) { println!("{u}") }`
 
 error: you seem to be trying to use `match` for an equality check. Consider using `if`
-  --> tests/ui/single_match.rs:486:5
+  --> tests/ui/single_match.rs:487:5
    |
 LL | /     match mac!(str) {
 LL | |         "foo" => println!("eq"),