src/lib.rs - platform/external/rust/crates/no-panic - Git at Google

 //! [![github]](https://github.com/dtolnay/no-panic)&ensp;[![crates-io]](https://crates.io/crates/no-panic)&ensp;[![docs-rs]](https://docs.rs/no-panic)
 //!
 //! [github]: https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github
 //! [crates-io]: https://img.shields.io/badge/crates.io-fc8d62?style=for-the-badge&labelColor=555555&logo=rust
 //! [docs-rs]: https://img.shields.io/badge/docs.rs-66c2a5?style=for-the-badge&labelColor=555555&logo=docs.rs
 //!
 //! <br>
 //!
 //! A Rust attribute macro to require that the compiler prove a function can't
 //! ever panic.
 //!
 //! ```toml
 //! [dependencies]
 //! no-panic = "0.1"
 //! ```
 //!
 //! ```
 //! use no_panic::no_panic;
 //!
 //! #[no_panic]
 //! fn demo(s: &str) -> &str {
 //!     &s[1..]
 //! }
 //!
 //! fn main() {
 //!     # fn demo(s: &str) -> &str {
 //!     #     &s[1..]
 //!     # }
 //!     #
 //!     println!("{}", demo("input string"));
 //! }
 //! ```
 //!
 //! If the function does panic (or the compiler fails to prove that the function
 //! cannot panic), the program fails to compile with a linker error that
 //! identifies the function name. Let's trigger that by passing a string that
 //! cannot be sliced at the first byte:
 //!
 //! ```should_panic
 //! # fn demo(s: &str) -> &str {
 //! #     &s[1..]
 //! # }
 //! #
 //! fn main() {
 //!     println!("{}", demo("\u{1f980}input string"));
 //! }
 //! ```
 //!
 //! ```console
 //!    Compiling no-panic-demo v0.0.1
 //! error: linking with `cc` failed: exit code: 1
 //!   |
 //!   = note: /no-panic-demo/target/release/deps/no_panic_demo-7170785b672ae322.no_p
 //! anic_demo1-cba7f4b666ccdbcbbf02b7348e5df1b2.rs.rcgu.o: In function `_$LT$no_pani
 //! c_demo..demo..__NoPanic$u20$as$u20$core..ops..drop..Drop$GT$::drop::h72f8f423002
 //! b8d9f':
 //!           no_panic_demo1-cba7f4b666ccdbcbbf02b7348e5df1b2.rs:(.text._ZN72_$LT$no
 //! _panic_demo..demo..__NoPanic$u20$as$u20$core..ops..drop..Drop$GT$4drop17h72f8f42
 //! 3002b8d9fE+0x2): undefined reference to `
 //!
 //!           ERROR[no-panic]: detected panic in function `demo`
 //!           '
 //!           collect2: error: ld returned 1 exit status
 //! ```
 //!
 //! The error is not stellar but notice the ERROR\[no-panic\] part at the end
 //! that provides the name of the offending function.
 //!
 //! *Compiler support: requires rustc 1.31+*
 //!
 //! <br>
 //!
 //! ## Caveats
 //!
 //! - Functions that require some amount of optimization to prove that they do
 //!   not panic may no longer compile in debug mode after being marked
 //!   `#[no_panic]`.
 //!
 //! - Panic detection happens at link time across the entire dependency graph,
 //!   so any Cargo commands that do not invoke a linker will not trigger panic
 //!   detection. This includes `cargo build` of library crates and `cargo check`
 //!   of binary and library crates.
 //!
 //! - The attribute is useless in code built with `panic = "abort"`.
 //!
 //! If you find that code requires optimization to pass `#[no_panic]`, either
 //! make no-panic an optional dependency that you only enable in release builds,
 //! or add a section like the following to Cargo.toml to enable very basic
 //! optimization in debug builds.
 //!
 //! ```toml
 //! [profile.dev]
 //! opt-level = 1
 //! ```
 //!
 //! If the code that you need to prove isn't panicking makes function calls to
 //! non-generic non-inline functions from a different crate, you may need thin
 //! LTO enabled for the linker to deduce those do not panic.
 //!
 //! ```toml
 //! [profile.release]
 //! lto = "thin"
 //! ```
 //!
 //! If you want no_panic to just assume that some function you call doesn't
 //! panic, and get Undefined Behavior if it does at runtime, see
 //! [dtolnay/no-panic#16]; try wrapping that call in an `unsafe extern "C"`
 //! wrapper.
 //!
 //! [dtolnay/no-panic#16]: https://github.com/dtolnay/no-panic/issues/16
 //!
 //! <br>
 //!
 //! ## Acknowledgments
 //!
 //! The linker error technique is based on [Kixunil]'s crate [`dont_panic`].
 //! Check out that crate for other convenient ways to require absence of panics.
 //!
 //! [Kixunil]: https://github.com/Kixunil
 //! [`dont_panic`]: https://github.com/Kixunil/dont_panic

 #![doc(html_root_url = "https://docs.rs/no-panic/0.1.21")]
 #![allow(
     clippy::doc_markdown,
     clippy::match_same_arms,
     clippy::missing_panics_doc
 )]
 #![cfg_attr(all(test, exhaustive), feature(non_exhaustive_omitted_patterns_lint))]

 extern crate proc_macro;

 use proc_macro::TokenStream;
 use proc_macro2::{Span, TokenStream as TokenStream2};
 use quote::quote;
 use syn::parse::{Error, Nothing, Result};
 use syn::{
     parse_quote, Attribute, FnArg, GenericArgument, Ident, ItemFn, Pat, PatType, Path,
     PathArguments, ReturnType, Token, Type, TypeInfer, TypeParamBound,
 };

 #[proc_macro_attribute]
 pub fn no_panic(args: TokenStream, input: TokenStream) -> TokenStream {
     let args = TokenStream2::from(args);
     let input = TokenStream2::from(input);
     let expanded = match parse(args, input.clone()) {
         Ok(function) => expand_no_panic(function),
         Err(parse_error) => {
             let compile_error = parse_error.to_compile_error();
             quote!(#compile_error #input)
         }
     };
     TokenStream::from(expanded)
 }

 fn parse(args: TokenStream2, input: TokenStream2) -> Result<ItemFn> {
     let function: ItemFn = syn::parse2(input)?;
     let _: Nothing = syn::parse2::<Nothing>(args)?;
     if function.sig.asyncness.is_some() {
         return Err(Error::new(
             Span::call_site(),
             "no_panic attribute on async fn is not supported",
         ));
     }
     Ok(function)
 }

 // Convert `Path<impl Trait>` to `Path<_>`
 fn make_impl_trait_wild(ret: &mut Type) {
     match ret {
         Type::ImplTrait(impl_trait) => {
             *ret = Type::Infer(TypeInfer {
                 underscore_token: Token![_](impl_trait.impl_token.span),
             });
         }
         Type::Array(ret) => make_impl_trait_wild(&mut ret.elem),
         Type::Group(ret) => make_impl_trait_wild(&mut ret.elem),
         Type::Paren(ret) => make_impl_trait_wild(&mut ret.elem),
         Type::Path(ret) => make_impl_trait_wild_in_path(&mut ret.path),
         Type::Ptr(ret) => make_impl_trait_wild(&mut ret.elem),
         Type::Reference(ret) => make_impl_trait_wild(&mut ret.elem),
         Type::Slice(ret) => make_impl_trait_wild(&mut ret.elem),
         Type::TraitObject(ret) => {
             for bound in &mut ret.bounds {
                 if let TypeParamBound::Trait(bound) = bound {
                     make_impl_trait_wild_in_path(&mut bound.path);
                 }
             }
         }
         Type::Tuple(ret) => ret.elems.iter_mut().for_each(make_impl_trait_wild),
         Type::BareFn(_) | Type::Infer(_) | Type::Macro(_) | Type::Never(_) | Type::Verbatim(_) => {}
         #[cfg_attr(all(test, exhaustive), deny(non_exhaustive_omitted_patterns))]
         _ => {}
     }
 }

 fn make_impl_trait_wild_in_path(path: &mut Path) {
     for segment in &mut path.segments {
         if let PathArguments::AngleBracketed(bracketed) = &mut segment.arguments {
             for arg in &mut bracketed.args {
                 if let GenericArgument::Type(arg) = arg {
                     make_impl_trait_wild(arg);
                 }
             }
         }
     }
 }

 fn expand_no_panic(mut function: ItemFn) -> TokenStream2 {
     let mut move_self = None;
     let mut arg_pat = Vec::new();
     let mut arg_val = Vec::new();
     for (i, input) in function.sig.inputs.iter_mut().enumerate() {
         let numbered = Ident::new(&format!("__arg{}", i), Span::call_site());
         match input {
             FnArg::Typed(PatType { pat, .. })
                 if match pat.as_ref() {
                     Pat::Ident(pat) => pat.ident != "self",
                     _ => true,
                 } =>
             {
                 arg_pat.push(quote!(#pat));
                 arg_val.push(quote!(#numbered));
                 *pat = parse_quote!(mut #numbered);
             }
             FnArg::Typed(_) | FnArg::Receiver(_) => {
                 move_self = Some(quote! {
                     if false {
                         loop {}
                         #[allow(unreachable_code)]
                         {
                             let __self = self;
                         }
                     }
                 });
             }
         }
     }

     let has_inline = function
         .attrs
         .iter()
         .flat_map(Attribute::parse_meta)
         .any(|meta| meta.path().is_ident("inline"));
     if !has_inline {
         function.attrs.push(parse_quote!(#[inline]));
     }

     let ret = match &function.sig.output {
         ReturnType::Default => quote!(-> ()),
         ReturnType::Type(arrow, output) => {
             let mut output = output.clone();
             make_impl_trait_wild(&mut output);
             quote!(#arrow #output)
         }
     };
     let stmts = function.block.stmts;
     let message = format!(
         "\n\nERROR[no-panic]: detected panic in function `{}`\n",
         function.sig.ident,
     );
     function.block = Box::new(parse_quote!({
         struct __NoPanic;
         extern "C" {
             #[link_name = #message]
             fn trigger() -> !;
         }
         impl core::ops::Drop for __NoPanic {
             fn drop(&mut self) {
                 unsafe {
                     trigger();
                 }
             }
         }
         let __guard = __NoPanic;
         let __result = (move || #ret {
             #move_self
             #(
                 let #arg_pat = #arg_val;
             )*
             #(#stmts)*
         })();
         core::mem::forget(__guard);
         __result
     }));

     quote!(#function)
 }
	//! [![github]](https://github.com/dtolnay/no-panic)&ensp;[![crates-io]](https://crates.io/crates/no-panic)&ensp;[![docs-rs]](https://docs.rs/no-panic)
	//!
	//! [github]: https://img.shields.io/badge/github-8da0cb?style=for-the-badge&labelColor=555555&logo=github
	//! [crates-io]: https://img.shields.io/badge/crates.io-fc8d62?style=for-the-badge&labelColor=555555&logo=rust
	//! [docs-rs]: https://img.shields.io/badge/docs.rs-66c2a5?style=for-the-badge&labelColor=555555&logo=docs.rs
	//!
	//! <br>
	//!
	//! A Rust attribute macro to require that the compiler prove a function can't
	//! ever panic.
	//!
	//! ```toml
	//! [dependencies]
	//! no-panic = "0.1"
	//! ```
	//!
	//! ```
	//! use no_panic::no_panic;
	//!
	//! #[no_panic]
	//! fn demo(s: &str) -> &str {
	//! &s[1..]
	//! }
	//!
	//! fn main() {
	//! # fn demo(s: &str) -> &str {
	//! # &s[1..]
	//! # }
	//! #
	//! println!("{}", demo("input string"));
	//! }
	//! ```
	//!
	//! If the function does panic (or the compiler fails to prove that the function
	//! cannot panic), the program fails to compile with a linker error that
	//! identifies the function name. Let's trigger that by passing a string that
	//! cannot be sliced at the first byte:
	//!
	//! ```should_panic
	//! # fn demo(s: &str) -> &str {
	//! # &s[1..]
	//! # }
	//! #
	//! fn main() {
	//! println!("{}", demo("\u{1f980}input string"));
	//! }
	//! ```
	//!
	//! ```console
	//! Compiling no-panic-demo v0.0.1
	//! error: linking with `cc` failed: exit code: 1
	//! \|
	//! = note: /no-panic-demo/target/release/deps/no_panic_demo-7170785b672ae322.no_p
	//! anic_demo1-cba7f4b666ccdbcbbf02b7348e5df1b2.rs.rcgu.o: In function `_$LT$no_pani
	//! c_demo..demo..__NoPanic$u20$as$u20$core..ops..drop..Drop$GT$::drop::h72f8f423002
	//! b8d9f':
	//! no_panic_demo1-cba7f4b666ccdbcbbf02b7348e5df1b2.rs:(.text._ZN72_$LT$no
	//! _panic_demo..demo..__NoPanic$u20$as$u20$core..ops..drop..Drop$GT$4drop17h72f8f42
	//! 3002b8d9fE+0x2): undefined reference to `
	//!
	//! ERROR[no-panic]: detected panic in function `demo`
	//! '
	//! collect2: error: ld returned 1 exit status
	//! ```
	//!
	//! The error is not stellar but notice the ERROR\[no-panic\] part at the end
	//! that provides the name of the offending function.
	//!
	//! Compiler support: requires rustc 1.31+
	//!
	//! <br>
	//!
	//! ## Caveats
	//!
	//! - Functions that require some amount of optimization to prove that they do
	//! not panic may no longer compile in debug mode after being marked
	//! `#[no_panic]`.
	//!
	//! - Panic detection happens at link time across the entire dependency graph,
	//! so any Cargo commands that do not invoke a linker will not trigger panic
	//! detection. This includes `cargo build` of library crates and `cargo check`
	//! of binary and library crates.
	//!
	//! - The attribute is useless in code built with `panic = "abort"`.
	//!
	//! If you find that code requires optimization to pass `#[no_panic]`, either
	//! make no-panic an optional dependency that you only enable in release builds,
	//! or add a section like the following to Cargo.toml to enable very basic
	//! optimization in debug builds.
	//!
	//! ```toml
	//! [profile.dev]
	//! opt-level = 1
	//! ```
	//!
	//! If the code that you need to prove isn't panicking makes function calls to
	//! non-generic non-inline functions from a different crate, you may need thin
	//! LTO enabled for the linker to deduce those do not panic.
	//!
	//! ```toml
	//! [profile.release]
	//! lto = "thin"
	//! ```
	//!
	//! If you want no_panic to just assume that some function you call doesn't
	//! panic, and get Undefined Behavior if it does at runtime, see
	//! [dtolnay/no-panic#16]; try wrapping that call in an `unsafe extern "C"`
	//! wrapper.
	//!
	//! [dtolnay/no-panic#16]: https://github.com/dtolnay/no-panic/issues/16
	//!
	//! <br>
	//!
	//! ## Acknowledgments
	//!
	//! The linker error technique is based on [Kixunil]'s crate [`dont_panic`].
	//! Check out that crate for other convenient ways to require absence of panics.
	//!
	//! [Kixunil]: https://github.com/Kixunil
	//! [`dont_panic`]: https://github.com/Kixunil/dont_panic

	#![doc(html_root_url = "https://docs.rs/no-panic/0.1.21")]
	#![allow(
	clippy::doc_markdown,
	clippy::match_same_arms,
	clippy::missing_panics_doc
	)]
	#![cfg_attr(all(test, exhaustive), feature(non_exhaustive_omitted_patterns_lint))]

	extern crate proc_macro;

	use proc_macro::TokenStream;
	use proc_macro2::{Span, TokenStream as TokenStream2};
	use quote::quote;
	use syn::parse::{Error, Nothing, Result};
	use syn::{
	parse_quote, Attribute, FnArg, GenericArgument, Ident, ItemFn, Pat, PatType, Path,
	PathArguments, ReturnType, Token, Type, TypeInfer, TypeParamBound,
	};

	#[proc_macro_attribute]
	pub fn no_panic(args: TokenStream, input: TokenStream) -> TokenStream {
	let args = TokenStream2::from(args);
	let input = TokenStream2::from(input);
	let expanded = match parse(args, input.clone()) {
	Ok(function) => expand_no_panic(function),
	Err(parse_error) => {
	let compile_error = parse_error.to_compile_error();
	quote!(#compile_error #input)
	}
	};
	TokenStream::from(expanded)
	}

	fn parse(args: TokenStream2, input: TokenStream2) -> Result<ItemFn> {
	let function: ItemFn = syn::parse2(input)?;
	let _: Nothing = syn::parse2::<Nothing>(args)?;
	if function.sig.asyncness.is_some() {
	return Err(Error::new(
	Span::call_site(),
	"no_panic attribute on async fn is not supported",
	));
	}
	Ok(function)
	}

	// Convert `Path<impl Trait>` to `Path<_>`
	fn make_impl_trait_wild(ret: &mut Type) {
	match ret {
	Type::ImplTrait(impl_trait) => {
	*ret = Type::Infer(TypeInfer {
	underscore_token: Token![_](impl_trait.impl_token.span),
	});
	}
	Type::Array(ret) => make_impl_trait_wild(&mut ret.elem),
	Type::Group(ret) => make_impl_trait_wild(&mut ret.elem),
	Type::Paren(ret) => make_impl_trait_wild(&mut ret.elem),
	Type::Path(ret) => make_impl_trait_wild_in_path(&mut ret.path),
	Type::Ptr(ret) => make_impl_trait_wild(&mut ret.elem),
	Type::Reference(ret) => make_impl_trait_wild(&mut ret.elem),
	Type::Slice(ret) => make_impl_trait_wild(&mut ret.elem),
	Type::TraitObject(ret) => {
	for bound in &mut ret.bounds {
	if let TypeParamBound::Trait(bound) = bound {
	make_impl_trait_wild_in_path(&mut bound.path);
	}
	}
	}
	Type::Tuple(ret) => ret.elems.iter_mut().for_each(make_impl_trait_wild),
	Type::BareFn(_) \| Type::Infer(_) \| Type::Macro(_) \| Type::Never(_) \| Type::Verbatim(_) => {}
	#[cfg_attr(all(test, exhaustive), deny(non_exhaustive_omitted_patterns))]
	_ => {}
	}
	}

	fn make_impl_trait_wild_in_path(path: &mut Path) {
	for segment in &mut path.segments {
	if let PathArguments::AngleBracketed(bracketed) = &mut segment.arguments {
	for arg in &mut bracketed.args {
	if let GenericArgument::Type(arg) = arg {
	make_impl_trait_wild(arg);
	}
	}
	}
	}
	}

	fn expand_no_panic(mut function: ItemFn) -> TokenStream2 {
	let mut move_self = None;
	let mut arg_pat = Vec::new();
	let mut arg_val = Vec::new();
	for (i, input) in function.sig.inputs.iter_mut().enumerate() {
	let numbered = Ident::new(&format!("__arg{}", i), Span::call_site());
	match input {
	FnArg::Typed(PatType { pat, .. })
	if match pat.as_ref() {
	Pat::Ident(pat) => pat.ident != "self",
	_ => true,
	} =>
	{
	arg_pat.push(quote!(#pat));
	arg_val.push(quote!(#numbered));
	*pat = parse_quote!(mut #numbered);
	}
	FnArg::Typed(_) \| FnArg::Receiver(_) => {
	move_self = Some(quote! {
	if false {
	loop {}
	#[allow(unreachable_code)]
	{
	let __self = self;
	}
	}
	});
	}
	}
	}

	let has_inline = function
	.attrs
	.iter()
	.flat_map(Attribute::parse_meta)
	.any(\|meta\| meta.path().is_ident("inline"));
	if !has_inline {
	function.attrs.push(parse_quote!(#[inline]));
	}

	let ret = match &function.sig.output {
	ReturnType::Default => quote!(-> ()),
	ReturnType::Type(arrow, output) => {
	let mut output = output.clone();
	make_impl_trait_wild(&mut output);
	quote!(#arrow #output)
	}
	};
	let stmts = function.block.stmts;
	let message = format!(
	"\n\nERROR[no-panic]: detected panic in function `{}`\n",
	function.sig.ident,
	);
	function.block = Box::new(parse_quote!({
	struct __NoPanic;
	extern "C" {
	#[link_name = #message]
	fn trigger() -> !;
	}
	impl core::ops::Drop for __NoPanic {
	fn drop(&mut self) {
	unsafe {
	trigger();
	}
	}
	}
	let __guard = __NoPanic;
	let __result = (move \|\| #ret {
	#move_self
	#(
	let #arg_pat = #arg_val;
	)*
	#(#stmts)*
	})();
	core::mem::forget(__guard);
	__result
	}));

	quote!(#function)
	}