Auto merge of rust-lang#134605 - jhpratt:rollup-quiss71, r=jhpratt

Rollup of 7 pull requests

Successful merges:

 - rust-lang#133087 (Detect missing `.` in method chain in `let` bindings and statements)
 - rust-lang#134575 (Handle `DropKind::ForLint` in coroutines correctly)
 - rust-lang#134576 (Improve prose around basic examples of Iter and IterMut)
 - rust-lang#134577 (Improve prose around `as_slice` example of Iter)
 - rust-lang#134579 (Improve prose around into_slice example of IterMut)
 - rust-lang#134593 (Less unwrap() in documentation)
 - rust-lang#134600 (Fix parenthesization of chained comparisons by pretty-printer)

r? `@ghost`
`@rustbot` modify labels: rollup

compiler/rustc_ast/src/util/parser.rs

@@ -153,9 +153,10 @@ impl AssocOp {
         match *self {
             Assign | AssignOp(_) => Fixity::Right,
             As | Multiply | Divide | Modulus | Add | Subtract | ShiftLeft | ShiftRight | BitAnd
-            | BitXor | BitOr | Less | Greater | LessEqual | GreaterEqual | Equal | NotEqual
-            | LAnd | LOr => Fixity::Left,
-            DotDot | DotDotEq => Fixity::None,
+            | BitXor | BitOr | LAnd | LOr => Fixity::Left,
+            Less | Greater | LessEqual | GreaterEqual | Equal | NotEqual | DotDot | DotDotEq => {
+                Fixity::None
+            }
         }
     }
 

compiler/rustc_mir_build/src/builder/scope.rs

@@ -1481,14 +1481,6 @@ fn build_scope_drops<'tcx>(
                 block = next;
             }
             DropKind::ForLint => {
-                // If the operand has been moved, and we are not on an unwind
-                // path, then don't generate the drop. (We only take this into
-                // account for non-unwind paths so as not to disturb the
-                // caching mechanism.)
-                if scope.moved_locals.iter().any(|&o| o == local) {
-                    continue;
-                }
-
                 // As in the `DropKind::Storage` case below:
                 // normally lint-related drops are not emitted for unwind,
                 // so we can just leave `unwind_to` unmodified, but in some
@@ -1500,6 +1492,14 @@ fn build_scope_drops<'tcx>(
                     unwind_to = unwind_drops.drops[unwind_to].next;
                 }
 
+                // If the operand has been moved, and we are not on an unwind
+                // path, then don't generate the drop. (We only take this into
+                // account for non-unwind paths so as not to disturb the
+                // caching mechanism.)
+                if scope.moved_locals.iter().any(|&o| o == local) {
+                    continue;
+                }
+
                 cfg.push(block, Statement {
                     source_info,
                     kind: StatementKind::BackwardIncompatibleDropHint {
@@ -1552,7 +1552,7 @@ impl<'a, 'tcx: 'a> Builder<'a, 'tcx> {
             let mut unwind_indices = IndexVec::from_elem_n(unwind_target, 1);
             for (drop_idx, drop_node) in drops.drops.iter_enumerated().skip(1) {
                 match drop_node.data.kind {
-                    DropKind::Storage => {
+                    DropKind::Storage | DropKind::ForLint => {
                         if is_coroutine {
                             let unwind_drop = self
                                 .scopes
@@ -1563,7 +1563,7 @@ impl<'a, 'tcx: 'a> Builder<'a, 'tcx> {
                             unwind_indices.push(unwind_indices[drop_node.next]);
                         }
                     }
-                    DropKind::Value | DropKind::ForLint => {
+                    DropKind::Value => {
                         let unwind_drop = self
                             .scopes
                             .unwind_drops

compiler/rustc_parse/src/parser/expr.rs

@@ -279,13 +279,9 @@ impl<'a> Parser<'a> {
                 break;
             }
 
-            let fixity = op.fixity();
-            let min_prec = match fixity {
+            let min_prec = match op.fixity() {
                 Fixity::Right => Bound::Included(prec),
-                Fixity::Left => Bound::Excluded(prec),
-                // We currently have no non-associative operators that are not handled above by
-                // the special cases. The code is here only for future convenience.
-                Fixity::None => Bound::Excluded(prec),
+                Fixity::Left | Fixity::None => Bound::Excluded(prec),
             };
             let (rhs, _) = self.with_res(restrictions - Restrictions::STMT_EXPR, |this| {
                 let attrs = this.parse_outer_attributes()?;
@@ -337,10 +333,6 @@ impl<'a> Parser<'a> {
                     self.dcx().span_bug(span, "AssocOp should have been handled by special case")
                 }
             };
-
-            if let Fixity::None = fixity {
-                break;
-            }
         }
 
         Ok((lhs, parsed_something))

compiler/rustc_parse/src/parser/stmt.rs

@@ -745,6 +745,51 @@ impl<'a> Parser<'a> {
         Ok(self.mk_block(stmts, s, lo.to(self.prev_token.span)))
     }
 
+    fn recover_missing_dot(&mut self, err: &mut Diag<'_>) {
+        let Some((ident, _)) = self.token.ident() else {
+            return;
+        };
+        if let Some(c) = ident.name.as_str().chars().next()
+            && c.is_uppercase()
+        {
+            return;
+        }
+        if self.token.is_reserved_ident() && !self.token.is_ident_named(kw::Await) {
+            return;
+        }
+        if self.prev_token.is_reserved_ident() && self.prev_token.is_ident_named(kw::Await) {
+            // Likely `foo.await bar`
+        } else if !self.prev_token.is_reserved_ident() && self.prev_token.is_ident() {
+            // Likely `foo bar`
+        } else if self.prev_token.kind == token::Question {
+            // `foo? bar`
+        } else if self.prev_token.kind == token::CloseDelim(Delimiter::Parenthesis) {
+            // `foo() bar`
+        } else {
+            return;
+        }
+        if self.token.span == self.prev_token.span {
+            // Account for syntax errors in proc-macros.
+            return;
+        }
+        if self.look_ahead(1, |t| [token::Semi, token::Question, token::Dot].contains(&t.kind)) {
+            err.span_suggestion_verbose(
+                self.prev_token.span.between(self.token.span),
+                "you might have meant to write a field access",
+                ".".to_string(),
+                Applicability::MaybeIncorrect,
+            );
+        }
+        if self.look_ahead(1, |t| t.kind == token::OpenDelim(Delimiter::Parenthesis)) {
+            err.span_suggestion_verbose(
+                self.prev_token.span.between(self.token.span),
+                "you might have meant to write a method call",
+                ".".to_string(),
+                Applicability::MaybeIncorrect,
+            );
+        }
+    }
+
     /// Parses a statement, including the trailing semicolon.
     pub fn parse_full_stmt(
         &mut self,
@@ -851,7 +896,8 @@ impl<'a> Parser<'a> {
                             Some(if recover.no() {
                                 res?
                             } else {
-                                res.unwrap_or_else(|e| {
+                                res.unwrap_or_else(|mut e| {
+                                    self.recover_missing_dot(&mut e);
                                     let guar = e.emit();
                                     self.recover_stmt();
                                     guar
@@ -872,7 +918,12 @@ impl<'a> Parser<'a> {
                 // We might be at the `,` in `let x = foo<bar, baz>;`. Try to recover.
                 match &mut local.kind {
                     LocalKind::Init(expr) | LocalKind::InitElse(expr, _) => {
-                        self.check_mistyped_turbofish_with_multiple_type_params(e, expr)?;
+                        self.check_mistyped_turbofish_with_multiple_type_params(e, expr).map_err(
+                            |mut e| {
+                                self.recover_missing_dot(&mut e);
+                                e
+                            },
+                        )?;
                         // We found `foo<bar, baz>`, have we fully recovered?
                         self.expect_semi()?;
                     }

library/alloc/src/collections/binary_heap/mod.rs

@@ -531,8 +531,7 @@ impl<T: Ord, A: Allocator> BinaryHeap<T, A> {
     /// heap.push(1);
     /// heap.push(5);
     /// heap.push(2);
-    /// {
-    ///     let mut val = heap.peek_mut().unwrap();
+    /// if let Some(mut val) = heap.peek_mut() {
     ///     *val = 0;
     /// }
     /// assert_eq!(heap.peek(), Some(&2));

library/core/src/cell/once.rs

@@ -262,7 +262,9 @@ impl<T> OnceCell<T> {
     ///
     /// let value = cell.get_mut_or_try_init(|| "1234".parse());
     /// assert_eq!(value, Ok(&mut 1234));
-    /// *value.unwrap() += 2;
+    ///
+    /// let Ok(value) = value else { return; };
+    /// *value += 2;
     /// assert_eq!(cell.get(), Some(&1236))
     /// ```
     #[unstable(feature = "once_cell_get_mut", issue = "121641")]
@@ -304,8 +306,8 @@ impl<T> OnceCell<T> {
     /// assert_eq!(cell.into_inner(), None);
     ///
     /// let cell = OnceCell::new();
-    /// cell.set("hello".to_string()).unwrap();
-    /// assert_eq!(cell.into_inner(), Some("hello".to_string()));
+    /// let _ = cell.set("hello".to_owned());
+    /// assert_eq!(cell.into_inner(), Some("hello".to_owned()));
     /// ```
     #[inline]
     #[stable(feature = "once_cell", since = "1.70.0")]
@@ -332,8 +334,8 @@ impl<T> OnceCell<T> {
     /// assert_eq!(cell.take(), None);
     ///
     /// let mut cell = OnceCell::new();
-    /// cell.set("hello".to_string()).unwrap();
-    /// assert_eq!(cell.take(), Some("hello".to_string()));
+    /// let _ = cell.set("hello".to_owned());
+    /// assert_eq!(cell.take(), Some("hello".to_owned()));
     /// assert_eq!(cell.get(), None);
     /// ```
     #[inline]

library/core/src/fmt/mod.rs

@@ -152,8 +152,9 @@ pub trait Write {
     /// }
     ///
     /// let mut buf = String::new();
-    /// writer(&mut buf, "hola").unwrap();
+    /// writer(&mut buf, "hola")?;
     /// assert_eq!(&buf, "hola");
+    /// # std::fmt::Result::Ok(())
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     fn write_str(&mut self, s: &str) -> Result;
@@ -179,9 +180,10 @@ pub trait Write {
     /// }
     ///
     /// let mut buf = String::new();
-    /// writer(&mut buf, 'a').unwrap();
-    /// writer(&mut buf, 'b').unwrap();
+    /// writer(&mut buf, 'a')?;
+    /// writer(&mut buf, 'b')?;
     /// assert_eq!(&buf, "ab");
+    /// # std::fmt::Result::Ok(())
     /// ```
     #[stable(feature = "fmt_write_char", since = "1.1.0")]
     fn write_char(&mut self, c: char) -> Result {
@@ -208,8 +210,9 @@ pub trait Write {
     /// }
     ///
     /// let mut buf = String::new();
-    /// writer(&mut buf, "world").unwrap();
+    /// writer(&mut buf, "world")?;
     /// assert_eq!(&buf, "world");
+    /// # std::fmt::Result::Ok(())
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     fn write_fmt(&mut self, args: Arguments<'_>) -> Result {

library/core/src/iter/sources/once.rs

@@ -34,7 +34,7 @@ use crate::iter::{FusedIterator, TrustedLen};
 /// use std::fs;
 /// use std::path::PathBuf;
 ///
-/// let dirs = fs::read_dir(".foo").unwrap();
+/// let dirs = fs::read_dir(".foo")?;
 ///
 /// // we need to convert from an iterator of DirEntry-s to an iterator of
 /// // PathBufs, so we use map
@@ -50,6 +50,7 @@ use crate::iter::{FusedIterator, TrustedLen};
 /// for f in files {
 ///     println!("{f:?}");
 /// }
+/// # std::io::Result::Ok(())
 /// ```
 #[stable(feature = "iter_once", since = "1.2.0")]
 pub fn once<T>(value: T) -> Once<T> {

library/core/src/iter/traits/iterator.rs

@@ -2564,7 +2564,7 @@ pub trait Iterator {
     /// # Example
     ///
     /// ```
-    /// let reduced: i32 = (1..10).reduce(|acc, e| acc + e).unwrap();
+    /// let reduced: i32 = (1..10).reduce(|acc, e| acc + e).unwrap_or(0);
     /// assert_eq!(reduced, 45);
     ///
     /// // Which is equivalent to doing it with `fold`:
@@ -3087,7 +3087,7 @@ pub trait Iterator {
     ///     [2.4, f32::NAN, 1.3]
     ///         .into_iter()
     ///         .reduce(f32::max)
-    ///         .unwrap(),
+    ///         .unwrap_or(0.),
     ///     2.4
     /// );
     /// ```
@@ -3123,7 +3123,7 @@ pub trait Iterator {
     ///     [2.4, f32::NAN, 1.3]
     ///         .into_iter()
     ///         .reduce(f32::min)
-    ///         .unwrap(),
+    ///         .unwrap_or(0.),
     ///     1.3
     /// );
     /// ```

library/core/src/option.rs

@@ -937,10 +937,16 @@ impl<T> Option<T> {
     /// Returns the contained [`Some`] value, consuming the `self` value.
     ///
     /// Because this function may panic, its use is generally discouraged.
+    /// Panics are meant for unrecoverable errors, and
+    /// [may abort the entire program][panic-abort].
+    ///
     /// Instead, prefer to use pattern matching and handle the [`None`]
     /// case explicitly, or call [`unwrap_or`], [`unwrap_or_else`], or
-    /// [`unwrap_or_default`].
+    /// [`unwrap_or_default`]. In functions returning `Option`, you can use
+    /// [the `?` (try) operator][try-option].
     ///
+    /// [panic-abort]: https://doc.rust-lang.org/book/ch09-01-unrecoverable-errors-with-panic.html
+    /// [try-option]: https://doc.rust-lang.org/book/ch09-02-recoverable-errors-with-result.html#where-the--operator-can-be-used
     /// [`unwrap_or`]: Option::unwrap_or
     /// [`unwrap_or_else`]: Option::unwrap_or_else
     /// [`unwrap_or_default`]: Option::unwrap_or_default

library/core/src/ptr/const_ptr.rs

@@ -502,11 +502,12 @@ impl<T: ?Sized> *const T {
     /// let mut out = String::new();
     /// while ptr != end_rounded_up {
     ///     unsafe {
-    ///         write!(&mut out, "{}, ", *ptr).unwrap();
+    ///         write!(&mut out, "{}, ", *ptr)?;
     ///     }
     ///     ptr = ptr.wrapping_offset(step);
     /// }
     /// assert_eq!(out.as_str(), "1, 3, 5, ");
+    /// # std::fmt::Result::Ok(())
     /// ```
     #[stable(feature = "ptr_wrapping_offset", since = "1.16.0")]
     #[must_use = "returns a new pointer rather than modifying its argument"]
@@ -1125,11 +1126,12 @@ impl<T: ?Sized> *const T {
     /// let mut out = String::new();
     /// while ptr != end_rounded_up {
     ///     unsafe {
-    ///         write!(&mut out, "{}, ", *ptr).unwrap();
+    ///         write!(&mut out, "{}, ", *ptr)?;
     ///     }
     ///     ptr = ptr.wrapping_add(step);
     /// }
     /// assert_eq!(out, "1, 3, 5, ");
+    /// # std::fmt::Result::Ok(())
     /// ```
     #[stable(feature = "pointer_methods", since = "1.26.0")]
     #[must_use = "returns a new pointer rather than modifying its argument"]
@@ -1203,11 +1205,12 @@ impl<T: ?Sized> *const T {
     /// let mut out = String::new();
     /// while ptr != start_rounded_down {
     ///     unsafe {
-    ///         write!(&mut out, "{}, ", *ptr).unwrap();
+    ///         write!(&mut out, "{}, ", *ptr)?;
     ///     }
     ///     ptr = ptr.wrapping_sub(step);
     /// }
     /// assert_eq!(out, "5, 3, 1, ");
+    /// # std::fmt::Result::Ok(())
     /// ```
     #[stable(feature = "pointer_methods", since = "1.26.0")]
     #[must_use = "returns a new pointer rather than modifying its argument"]

library/core/src/result.rs

@@ -1065,10 +1065,15 @@ impl<T, E> Result<T, E> {
     /// Returns the contained [`Ok`] value, consuming the `self` value.
     ///
     /// Because this function may panic, its use is generally discouraged.
-    /// Instead, prefer to use pattern matching and handle the [`Err`]
-    /// case explicitly, or call [`unwrap_or`], [`unwrap_or_else`], or
-    /// [`unwrap_or_default`].
+    /// Panics are meant for unrecoverable errors, and
+    /// [may abort the entire program][panic-abort].
+    ///
+    /// Instead, prefer to use [the `?` (try) operator][try-operator], or pattern matching
+    /// to handle the [`Err`] case explicitly, or call [`unwrap_or`],
+    /// [`unwrap_or_else`], or [`unwrap_or_default`].
     ///
+    /// [panic-abort]: https://doc.rust-lang.org/book/ch09-01-unrecoverable-errors-with-panic.html
+    /// [try-operator]: https://doc.rust-lang.org/book/ch09-02-recoverable-errors-with-result.html#a-shortcut-for-propagating-errors-the--operator
     /// [`unwrap_or`]: Result::unwrap_or
     /// [`unwrap_or_else`]: Result::unwrap_or_else
     /// [`unwrap_or_default`]: Result::unwrap_or_default