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extern crate proc_macro;
use proc_macro::TokenStream;
use proc_macro2::{Group, Span, TokenStream as TokenStream2, TokenTree};
use quote::quote;
use syn::visit_mut::VisitMut;
use syn::{
parse_macro_input, parse_quote, Attribute, ExprPath, FnArg,
Ident, Item, ItemFn, Macro, ReturnType,
PatType,
};
struct ReplaceSelf;
impl VisitMut for ReplaceSelf {
fn visit_expr_path_mut(&mut self, i: &mut ExprPath) {
if i.qself.is_none() && i.path.is_ident("self") {
prepend_underscores_to_self(&mut i.path.segments[0].ident);
}
}
fn visit_macro_mut(&mut self, i: &mut Macro) {
if !contains_fn(i.tokens.clone()) {
i.tokens = fold_token_stream(i.tokens.clone());
}
}
fn visit_item_mut(&mut self, _i: &mut Item) {
}
}
fn contains_fn(tokens: TokenStream2) -> bool {
tokens.into_iter().any(|tt| match tt {
TokenTree::Ident(ident) => ident == "fn",
TokenTree::Group(group) => contains_fn(group.stream()),
_ => false,
})
}
fn fold_token_stream(tokens: TokenStream2) -> TokenStream2 {
tokens.into_iter()
.map(|tt| match tt {
TokenTree::Ident(mut ident) => {
prepend_underscores_to_self(&mut ident);
TokenTree::Ident(ident)
}
TokenTree::Group(group) => {
let content = fold_token_stream(group.stream());
TokenTree::Group(Group::new(group.delimiter(), content))
}
other => other,
})
.collect()
}
fn prepend_underscores_to_self(ident: &mut Ident) {
if ident == "self" {
*ident = Ident::new("__self", Span::call_site());
}
}
#[proc_macro_attribute]
pub fn no_panic(args: TokenStream, function: TokenStream) -> TokenStream {
assert!(args.is_empty());
let mut function = parse_macro_input!(function as ItemFn);
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, .. }) => {
arg_pat.push(quote!(#pat));
arg_val.push(quote!(#numbered));
*pat = parse_quote!(mut #numbered);
}
FnArg::Receiver(receiver) => {
let self_token = receiver.self_token;
arg_val.push(quote!(#self_token));
if receiver.reference.is_some() {
arg_pat.push(quote!(__self));
} else {
let mutability = &mut receiver.mutability;
arg_pat.push(quote!(#mutability __self));
*mutability = None;
}
ReplaceSelf.visit_block_mut(&mut function.block);
}
}
}
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!(-> ()),
output @ ReturnType::Type(..) => quote!(#output),
};
let body = function.block;
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 {
#(
let #arg_pat = #arg_val;
)*
#body
})();
core::mem::forget(__guard);
__result
}));
TokenStream::from(quote!(#function))
}