From cf9610f9116d55c5a66ef9f1faecacabd93a9322 Mon Sep 17 00:00:00 2001 From: Linus Torvalds Date: Mon, 24 Aug 2026 08:46:03 -0700 Subject: Merge tag 'pinctrl-v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl Pull pin control updates from Linus Walleij: "Core changes: - Use the non-blocking mux_state_try_select() in the generic MUX pin control back-end - Free pin maps on pinctrl_generic_to_map() failure in the core helpers New hardware pin control: - Qualcomm Maili TLMM SoC, PMG1110 PMIC, and Eliza LPASS LPI TLMM SoC (this is for the low power audio, LPASS = Low Power Audio SubSystem portions) - Upboard support on top of the Intel pin controller - Apple T6030 and T6031 support (just compatible strings) - Samsung Exynos 8855 SoC - Mediatek MT6858 SoC - Rockchip RK3308B and RV1106 SoCs - Airoha EN7523 and AN7563 SoCs Improvements: - Qualcomm TLMM GPIOs are unconditionally marked as wakeup capable - Qualcomm improvements on top of the Qualcomm PDC (power domain controller) irqchip improvements from tglx:s tree - Qualcomm IPQ806x and IPQ9650 non-urgent pin grop fixups - The NPCM8xx driver has been put into shape fixing many pin and group definitions - Some non-urgent Tegra 264 pin assignments are fixed up - Some non-urgent fixups to Airoha AN7581 and AN7583 registers and pin assignments, missing features etc" * tag 'pinctrl-v7.3-1' of git://git.kernel.org/pub/scm/linux/kernel/git/linusw/linux-pinctrl: (130 commits) dt-bindings: pinctrl: Convert TI DA850 pupd to DT schema pinctrl: meson: sync some modify from A4 pinctrl: meson: a4: Add input enable pin configuration pinctrl: realtek: rtd1625: remove unused group name spdif_sel pinctrl: realtek: rtd1625: fix base_bit for VE4 GPIO 13 dt-bindings: pinctrl: microchip,pic32mzda-pinctrl: Convert to DT schema Revert "Merge branch 'ib-rsk7204' into devel" pinctrl: rockchip: Add RV1106 pinctrl support dt-bindings: pinctrl: rockchip: Add RV1106 compatible pinctrl: rockchip: Decode drive strength in the get function pinctrl: fix PINCTRL_GENERIC_MUX not always being selectable pinctrl: airoha: add support of an7563 SoC dt-bindings: pinctrl: airoha: add support of an7563 pin controller pinctrl: airoha: try to find chip scu node by phandle first pinctrl: airoha: add support of en7523 SoC dt-bindings: pinctrl: airoha: add support of en7523 pin controller pinctrl: airoha: an7583: add support for olt pinmux pinctrl: airoha: an7583: add support for pon_alt pinmux pinctrl: airoha: an7583: add support for npu_uart pinmux dt-bindings: pinctrl: airoha: an7583: add missed features ... --- rust/syn/discouraged.rs | 227 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 227 insertions(+) create mode 100644 rust/syn/discouraged.rs (limited to 'rust/syn/discouraged.rs') diff --git a/rust/syn/discouraged.rs b/rust/syn/discouraged.rs new file mode 100644 index 000000000..2acd631ec --- /dev/null +++ b/rust/syn/discouraged.rs @@ -0,0 +1,227 @@ +// SPDX-License-Identifier: Apache-2.0 OR MIT + +//! Extensions to the parsing API with niche applicability. + +use crate::buffer::Cursor; +use crate::error::Result; +use crate::parse::{inner_unexpected, ParseBuffer, Unexpected}; +use proc_macro2::extra::DelimSpan; +use proc_macro2::Delimiter; +use std::cell::Cell; +use std::mem; +use std::rc::Rc; + +/// Extensions to the `ParseStream` API to support speculative parsing. +pub trait Speculative { + /// Advance this parse stream to the position of a forked parse stream. + /// + /// This is the opposite operation to [`ParseStream::fork`]. You can fork a + /// parse stream, perform some speculative parsing, then join the original + /// stream to the fork to "commit" the parsing from the fork to the main + /// stream. + /// + /// If you can avoid doing this, you should, as it limits the ability to + /// generate useful errors. That said, it is often the only way to parse + /// syntax of the form `A* B*` for arbitrary syntax `A` and `B`. The problem + /// is that when the fork fails to parse an `A`, it's impossible to tell + /// whether that was because of a syntax error and the user meant to provide + /// an `A`, or that the `A`s are finished and it's time to start parsing + /// `B`s. Use with care. + /// + /// Also note that if `A` is a subset of `B`, `A* B*` can be parsed by + /// parsing `B*` and removing the leading members of `A` from the + /// repetition, bypassing the need to involve the downsides associated with + /// speculative parsing. + /// + /// [`ParseStream::fork`]: ParseBuffer::fork + /// + /// # Example + /// + /// There has been chatter about the possibility of making the colons in the + /// turbofish syntax like `path::to::` no longer required by accepting + /// `path::to` in expression position. Specifically, according to [RFC + /// 2544], [`PathSegment`] parsing should always try to consume a following + /// `<` token as the start of generic arguments, and reset to the `<` if + /// that fails (e.g. the token is acting as a less-than operator). + /// + /// This is the exact kind of parsing behavior which requires the "fork, + /// try, commit" behavior that [`ParseStream::fork`] discourages. With + /// `advance_to`, we can avoid having to parse the speculatively parsed + /// content a second time. + /// + /// This change in behavior can be implemented in syn by replacing just the + /// `Parse` implementation for `PathSegment`: + /// + /// ``` + /// # use syn::ext::IdentExt; + /// use syn::parse::discouraged::Speculative; + /// # use syn::parse::{Parse, ParseStream}; + /// # use syn::{Ident, PathArguments, Result, Token}; + /// + /// pub struct PathSegment { + /// pub ident: Ident, + /// pub arguments: PathArguments, + /// } + /// # + /// # impl From for PathSegment + /// # where + /// # T: Into, + /// # { + /// # fn from(ident: T) -> Self { + /// # PathSegment { + /// # ident: ident.into(), + /// # arguments: PathArguments::None, + /// # } + /// # } + /// # } + /// + /// impl Parse for PathSegment { + /// fn parse(input: ParseStream) -> Result { + /// if input.peek(Token![super]) + /// || input.peek(Token![self]) + /// || input.peek(Token![Self]) + /// || input.peek(Token![crate]) + /// { + /// let ident = input.call(Ident::parse_any)?; + /// return Ok(PathSegment::from(ident)); + /// } + /// + /// let ident = input.parse()?; + /// if input.peek(Token![::]) && input.peek3(Token![<]) { + /// return Ok(PathSegment { + /// ident, + /// arguments: PathArguments::AngleBracketed(input.parse()?), + /// }); + /// } + /// if input.peek(Token![<]) && !input.peek(Token![<=]) { + /// let fork = input.fork(); + /// if let Ok(arguments) = fork.parse() { + /// input.advance_to(&fork); + /// return Ok(PathSegment { + /// ident, + /// arguments: PathArguments::AngleBracketed(arguments), + /// }); + /// } + /// } + /// Ok(PathSegment::from(ident)) + /// } + /// } + /// + /// # syn::parse_str::("a").unwrap(); + /// ``` + /// + /// # Drawbacks + /// + /// The main drawback of this style of speculative parsing is in error + /// presentation. Even if the lookahead is the "correct" parse, the error + /// that is shown is that of the "fallback" parse. To use the same example + /// as the turbofish above, take the following unfinished "turbofish": + /// + /// ```text + /// let _ = f<&'a fn(), for<'a> serde::>(); + /// ``` + /// + /// If this is parsed as generic arguments, we can provide the error message + /// + /// ```text + /// error: expected identifier + /// --> src.rs:L:C + /// | + /// L | let _ = f<&'a fn(), for<'a> serde::>(); + /// | ^ + /// ``` + /// + /// but if parsed using the above speculative parsing, it falls back to + /// assuming that the `<` is a less-than when it fails to parse the generic + /// arguments, and tries to interpret the `&'a` as the start of a labelled + /// loop, resulting in the much less helpful error + /// + /// ```text + /// error: expected `:` + /// --> src.rs:L:C + /// | + /// L | let _ = f<&'a fn(), for<'a> serde::>(); + /// | ^^ + /// ``` + /// + /// This can be mitigated with various heuristics (two examples: show both + /// forks' parse errors, or show the one that consumed more tokens), but + /// when you can control the grammar, sticking to something that can be + /// parsed LL(3) and without the LL(*) speculative parsing this makes + /// possible, displaying reasonable errors becomes much more simple. + /// + /// [RFC 2544]: https://github.com/rust-lang/rfcs/pull/2544 + /// [`PathSegment`]: crate::PathSegment + /// + /// # Performance + /// + /// This method performs a cheap fixed amount of work that does not depend + /// on how far apart the two streams are positioned. + /// + /// # Panics + /// + /// The forked stream in the argument of `advance_to` must have been + /// obtained by forking `self`. Attempting to advance to any other stream + /// will cause a panic. + fn advance_to(&self, fork: &Self); +} + +impl<'a> Speculative for ParseBuffer<'a> { + fn advance_to(&self, fork: &Self) { + if !crate::buffer::same_scope(self.cursor(), fork.cursor()) { + panic!("fork was not derived from the advancing parse stream"); + } + + let (self_unexp, self_sp) = inner_unexpected(self); + let (fork_unexp, fork_sp) = inner_unexpected(fork); + if !Rc::ptr_eq(&self_unexp, &fork_unexp) { + match (fork_sp, self_sp) { + // Unexpected set on the fork, but not on `self`, copy it over. + (Some((span, delimiter)), None) => { + self_unexp.set(Unexpected::Some(span, delimiter)); + } + // Unexpected unset. Use chain to propagate errors from fork. + (None, None) => { + fork_unexp.set(Unexpected::Chain(self_unexp)); + + // Ensure toplevel 'unexpected' tokens from the fork don't + // propagate up the chain by replacing the root `unexpected` + // pointer, only 'unexpected' tokens from existing group + // parsers should propagate. + fork.unexpected + .set(Some(Rc::new(Cell::new(Unexpected::None)))); + } + // Unexpected has been set on `self`. No changes needed. + (_, Some(_)) => {} + } + } + + // See comment on `cell` in the struct definition. + self.cell + .set(unsafe { mem::transmute::>(fork.cursor()) }); + } +} + +/// Extensions to the `ParseStream` API to support manipulating invisible +/// delimiters the same as if they were visible. +pub trait AnyDelimiter { + /// Returns the delimiter, the span of the delimiter token, and the nested + /// contents for further parsing. + fn parse_any_delimiter(&self) -> Result<(Delimiter, DelimSpan, ParseBuffer)>; +} + +impl<'a> AnyDelimiter for ParseBuffer<'a> { + fn parse_any_delimiter(&self) -> Result<(Delimiter, DelimSpan, ParseBuffer)> { + self.step(|cursor| { + if let Some((content, delimiter, span, rest)) = cursor.any_group() { + let scope = span.close(); + let nested = crate::parse::advance_step_cursor(cursor, content); + let unexpected = crate::parse::get_unexpected(self); + let content = crate::parse::new_parse_buffer(scope, nested, unexpected); + Ok(((delimiter, span, content), rest)) + } else { + Err(cursor.error("expected any delimiter")) + } + }) + } +} -- cgit v1.3.1