Rollup merge of rust-lang#81236 - estebank:everybody-loop-now, r=oli-obk

Gracefully handle loop labels missing leading `'` in different positions

Fix rust-lang#81192.

* Account for labels when suggesting `loop` instead of `while true`
* Suggest `'a` when given `a` only when appropriate
* Add loop head span to hir
* Tweak error for invalid `break expr`
* Add more misspelled label tests
* Avoid emitting redundant "unused label" lint
* Parse loop labels missing a leading `'`

Each commit can be reviewed in isolation.

Author: m-ou-se

clippy_lints/src/loops.rs

@@ -533,7 +533,7 @@ impl<'tcx> LateLintPass<'tcx> for Loops {
         }
 
         // check for never_loop
-        if let ExprKind::Loop(ref block, _, _) = expr.kind {
+        if let ExprKind::Loop(ref block, _, _, _) = expr.kind {
             match never_loop_block(block, expr.hir_id) {
                 NeverLoopResult::AlwaysBreak => span_lint(cx, NEVER_LOOP, expr.span, "this loop never actually loops"),
                 NeverLoopResult::MayContinueMainLoop | NeverLoopResult::Otherwise => (),
@@ -543,7 +543,7 @@ impl<'tcx> LateLintPass<'tcx> for Loops {
         // check for `loop { if let {} else break }` that could be `while let`
         // (also matches an explicit "match" instead of "if let")
         // (even if the "match" or "if let" is used for declaration)
-        if let ExprKind::Loop(ref block, _, LoopSource::Loop) = expr.kind {
+        if let ExprKind::Loop(ref block, _, LoopSource::Loop, _) = expr.kind {
             // also check for empty `loop {}` statements, skipping those in #[panic_handler]
             if block.stmts.is_empty() && block.expr.is_none() && !is_in_panic_handler(cx, expr) {
                 let msg = "empty `loop {}` wastes CPU cycles";
@@ -738,7 +738,7 @@ fn never_loop_expr(expr: &Expr<'_>, main_loop_id: HirId) -> NeverLoopResult {
         | ExprKind::Assign(ref e1, ref e2, _)
         | ExprKind::AssignOp(_, ref e1, ref e2)
         | ExprKind::Index(ref e1, ref e2) => never_loop_expr_all(&mut [&**e1, &**e2].iter().cloned(), main_loop_id),
-        ExprKind::Loop(ref b, _, _) => {
+        ExprKind::Loop(ref b, _, _, _) => {
             // Break can come from the inner loop so remove them.
             absorb_break(&never_loop_block(b, main_loop_id))
         },
@@ -1314,7 +1314,7 @@ impl<'a, 'tcx> Visitor<'tcx> for SameItemPushVisitor<'a, 'tcx> {
     fn visit_expr(&mut self, expr: &'tcx Expr<'_>) {
         match &expr.kind {
             // Non-determinism may occur ... don't give a lint
-            ExprKind::Loop(_, _, _) | ExprKind::Match(_, _, _) => self.should_lint = false,
+            ExprKind::Loop(..) | ExprKind::Match(..) => self.should_lint = false,
             ExprKind::Block(block, _) => self.visit_block(block),
             _ => {},
         }

clippy_lints/src/needless_continue.rs

@@ -221,7 +221,7 @@ where
 {
     if let ast::ExprKind::While(_, loop_block, label)
     | ast::ExprKind::ForLoop(_, _, loop_block, label)
-    | ast::ExprKind::Loop(loop_block, label) = &expr.kind
+    | ast::ExprKind::Loop(loop_block, label, ..) = &expr.kind
     {
         func(loop_block, label.as_ref());
     }

clippy_lints/src/shadow.rs

@@ -325,7 +325,7 @@ fn check_expr<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, bindings: &mut
         | ExprKind::Field(ref e, _)
         | ExprKind::AddrOf(_, _, ref e)
         | ExprKind::Box(ref e) => check_expr(cx, e, bindings),
-        ExprKind::Block(ref block, _) | ExprKind::Loop(ref block, _, _) => check_block(cx, block, bindings),
+        ExprKind::Block(ref block, _) | ExprKind::Loop(ref block, ..) => check_block(cx, block, bindings),
         // ExprKind::Call
         // ExprKind::MethodCall
         ExprKind::Array(v) | ExprKind::Tup(v) => {

clippy_lints/src/utils/author.rs

@@ -317,7 +317,7 @@ impl<'tcx> Visitor<'tcx> for PrintVisitor {
                 self.current = cast_pat;
                 self.visit_expr(expr);
             },
-            ExprKind::Loop(ref body, _, desugaring) => {
+            ExprKind::Loop(ref body, _, desugaring, _) => {
                 let body_pat = self.next("body");
                 let des = loop_desugaring_name(desugaring);
                 let label_pat = self.next("label");

clippy_lints/src/utils/higher.rs

@@ -142,7 +142,7 @@ pub fn for_loop<'tcx>(
         if let hir::ExprKind::Match(ref iterexpr, ref arms, hir::MatchSource::ForLoopDesugar) = expr.kind;
         if let hir::ExprKind::Call(_, ref iterargs) = iterexpr.kind;
         if iterargs.len() == 1 && arms.len() == 1 && arms[0].guard.is_none();
-        if let hir::ExprKind::Loop(ref block, _, _) = arms[0].body.kind;
+        if let hir::ExprKind::Loop(ref block, ..) = arms[0].body.kind;
         if block.expr.is_none();
         if let [ _, _, ref let_stmt, ref body ] = *block.stmts;
         if let hir::StmtKind::Local(ref local) = let_stmt.kind;
@@ -158,7 +158,7 @@ pub fn for_loop<'tcx>(
 /// `while cond { body }` becomes `(cond, body)`.
 pub fn while_loop<'tcx>(expr: &'tcx hir::Expr<'tcx>) -> Option<(&'tcx hir::Expr<'tcx>, &'tcx hir::Expr<'tcx>)> {
     if_chain! {
-        if let hir::ExprKind::Loop(block, _, hir::LoopSource::While) = &expr.kind;
+        if let hir::ExprKind::Loop(block, _, hir::LoopSource::While, _) = &expr.kind;
         if let hir::Block { expr: Some(expr), .. } = &**block;
         if let hir::ExprKind::Match(cond, arms, hir::MatchSource::WhileDesugar) = &expr.kind;
         if let hir::ExprKind::DropTemps(cond) = &cond.kind;

clippy_lints/src/utils/hir_utils.rs

@@ -123,7 +123,7 @@ impl<'a, 'tcx> SpanlessEq<'a, 'tcx> {
                 self.eq_expr(lc, rc) && self.eq_expr(&**lt, &**rt) && both(le, re, |l, r| self.eq_expr(l, r))
             },
             (&ExprKind::Lit(ref l), &ExprKind::Lit(ref r)) => l.node == r.node,
-            (&ExprKind::Loop(ref lb, ref ll, ref lls), &ExprKind::Loop(ref rb, ref rl, ref rls)) => {
+            (&ExprKind::Loop(ref lb, ref ll, ref lls, _), &ExprKind::Loop(ref rb, ref rl, ref rls, _)) => {
                 lls == rls && self.eq_block(lb, rb) && both(ll, rl, |l, r| l.ident.name == r.ident.name)
             },
             (&ExprKind::Match(ref le, ref la, ref ls), &ExprKind::Match(ref re, ref ra, ref rs)) => {
@@ -560,7 +560,7 @@ impl<'a, 'tcx> SpanlessHash<'a, 'tcx> {
             ExprKind::Lit(ref l) => {
                 l.node.hash(&mut self.s);
             },
-            ExprKind::Loop(ref b, ref i, _) => {
+            ExprKind::Loop(ref b, ref i, ..) => {
                 self.hash_block(b);
                 if let Some(i) = *i {
                     self.hash_name(i.ident.name);