1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827
use std::iter;
use proc_macro2::TokenStream;
use quote::{quote, quote_spanned, ToTokens};
use syn::visit_mut::VisitMut;
use syn::{
punctuated::Punctuated, spanned::Spanned, Block, Expr, ExprAsync, ExprCall, FieldPat, FnArg,
Ident, Item, ItemFn, Pat, PatIdent, PatReference, PatStruct, PatTuple, PatTupleStruct, PatType,
Path, ReturnType, Signature, Stmt, Token, Type, TypePath,
};
use crate::{
attr::{Field, Fields, FormatMode, InstrumentArgs, Level},
MaybeItemFn, MaybeItemFnRef,
};
/// Given an existing function, generate an instrumented version of that function
pub(crate) fn gen_function<'a, B: ToTokens + 'a>(
input: MaybeItemFnRef<'a, B>,
args: InstrumentArgs,
instrumented_function_name: &str,
self_type: Option<&TypePath>,
) -> proc_macro2::TokenStream {
// these are needed ahead of time, as ItemFn contains the function body _and_
// isn't representable inside a quote!/quote_spanned! macro
// (Syn's ToTokens isn't implemented for ItemFn)
let MaybeItemFnRef {
outer_attrs,
inner_attrs,
vis,
sig,
block,
} = input;
let Signature {
output,
inputs: params,
unsafety,
asyncness,
constness,
abi,
ident,
generics:
syn::Generics {
params: gen_params,
where_clause,
..
},
..
} = sig;
let warnings = args.warnings();
let (return_type, return_span) = if let ReturnType::Type(_, return_type) = &output {
(erase_impl_trait(return_type), return_type.span())
} else {
// Point at function name if we don't have an explicit return type
(syn::parse_quote! { () }, ident.span())
};
// Install a fake return statement as the first thing in the function
// body, so that we eagerly infer that the return type is what we
// declared in the async fn signature.
// The `#[allow(..)]` is given because the return statement is
// unreachable, but does affect inference, so it needs to be written
// exactly that way for it to do its magic.
let fake_return_edge = quote_spanned! {return_span=>
#[allow(
unknown_lints, unreachable_code, clippy::diverging_sub_expression,
clippy::let_unit_value, clippy::unreachable, clippy::let_with_type_underscore,
clippy::empty_loop
)]
if false {
let __tracing_attr_fake_return: #return_type = loop {};
return __tracing_attr_fake_return;
}
};
let block = quote! {
{
#fake_return_edge
#block
}
};
let body = gen_block(
&block,
params,
asyncness.is_some(),
args,
instrumented_function_name,
self_type,
);
quote!(
#(#outer_attrs) *
#vis #constness #unsafety #asyncness #abi fn #ident<#gen_params>(#params) #output
#where_clause
{
#(#inner_attrs) *
#warnings
#body
}
)
}
/// Instrument a block
fn gen_block<B: ToTokens>(
block: &B,
params: &Punctuated<FnArg, Token![,]>,
async_context: bool,
mut args: InstrumentArgs,
instrumented_function_name: &str,
self_type: Option<&TypePath>,
) -> proc_macro2::TokenStream {
// generate the span's name
let span_name = args
// did the user override the span's name?
.name
.as_ref()
.map(|name| quote!(#name))
.unwrap_or_else(|| quote!(#instrumented_function_name));
let args_level = args.level();
let level = args_level.clone();
let follows_from = args.follows_from.iter();
let follows_from = quote! {
#(for cause in #follows_from {
__tracing_attr_span.follows_from(cause);
})*
};
// generate this inside a closure, so we can return early on errors.
let span = (|| {
// Pull out the arguments-to-be-skipped first, so we can filter results
// below.
let param_names: Vec<(Ident, (Ident, RecordType))> = params
.clone()
.into_iter()
.flat_map(|param| match param {
FnArg::Typed(PatType { pat, ty, .. }) => {
param_names(*pat, RecordType::parse_from_ty(&ty))
}
FnArg::Receiver(_) => Box::new(iter::once((
Ident::new("self", param.span()),
RecordType::Debug,
))),
})
// Little dance with new (user-exposed) names and old (internal)
// names of identifiers. That way, we could do the following
// even though async_trait (<=0.1.43) rewrites "self" as "_self":
// ```
// #[async_trait]
// impl Foo for FooImpl {
// #[instrument(skip(self))]
// async fn foo(&self, v: usize) {}
// }
// ```
.map(|(x, record_type)| {
// if we are inside a function generated by async-trait <=0.1.43, we need to
// take care to rewrite "_self" as "self" for 'user convenience'
if self_type.is_some() && x == "_self" {
(Ident::new("self", x.span()), (x, record_type))
} else {
(x.clone(), (x, record_type))
}
})
.collect();
for skip in &args.skips {
if !param_names.iter().map(|(user, _)| user).any(|y| y == skip) {
return quote_spanned! {skip.span()=>
compile_error!("attempting to skip non-existent parameter")
};
}
}
let target = args.target();
let parent = args.parent.iter();
// filter out skipped fields
let quoted_fields: Vec<_> = param_names
.iter()
.filter(|(param, _)| {
if args.skip_all || args.skips.contains(param) {
return false;
}
// If any parameters have the same name as a custom field, skip
// and allow them to be formatted by the custom field.
if let Some(ref fields) = args.fields {
fields.0.iter().all(|Field { ref name, .. }| {
let first = name.first();
first != name.last() || !first.iter().any(|name| name == ¶m)
})
} else {
true
}
})
.map(|(user_name, (real_name, record_type))| match record_type {
RecordType::Value => quote!(#user_name = #real_name),
RecordType::Debug => quote!(#user_name = tracing::field::debug(&#real_name)),
})
.collect();
// replace every use of a variable with its original name
if let Some(Fields(ref mut fields)) = args.fields {
let mut replacer = IdentAndTypesRenamer {
idents: param_names.into_iter().map(|(a, (b, _))| (a, b)).collect(),
types: Vec::new(),
};
// when async-trait <=0.1.43 is in use, replace instances
// of the "Self" type inside the fields values
if let Some(self_type) = self_type {
replacer.types.push(("Self", self_type.clone()));
}
for e in fields.iter_mut().filter_map(|f| f.value.as_mut()) {
syn::visit_mut::visit_expr_mut(&mut replacer, e);
}
}
let custom_fields = &args.fields;
quote!(tracing::span!(
target: #target,
#(parent: #parent,)*
#level,
#span_name,
#(#quoted_fields,)*
#custom_fields
))
})();
let target = args.target();
let err_event = match args.err_args {
Some(event_args) => {
let level_tokens = event_args.level(Level::Error);
match event_args.mode {
FormatMode::Default | FormatMode::Display => Some(quote!(
tracing::event!(target: #target, #level_tokens, error = %e)
)),
FormatMode::Debug => Some(quote!(
tracing::event!(target: #target, #level_tokens, error = ?e)
)),
}
}
_ => None,
};
let ret_event = match args.ret_args {
Some(event_args) => {
let level_tokens = event_args.level(args_level);
match event_args.mode {
FormatMode::Display => Some(quote!(
tracing::event!(target: #target, #level_tokens, return = %x)
)),
FormatMode::Default | FormatMode::Debug => Some(quote!(
tracing::event!(target: #target, #level_tokens, return = ?x)
)),
}
}
_ => None,
};
// Generate the instrumented function body.
// If the function is an `async fn`, this will wrap it in an async block,
// which is `instrument`ed using `tracing-futures`. Otherwise, this will
// enter the span and then perform the rest of the body.
// If `err` is in args, instrument any resulting `Err`s.
// If `ret` is in args, instrument any resulting `Ok`s when the function
// returns `Result`s, otherwise instrument any resulting values.
if async_context {
let mk_fut = match (err_event, ret_event) {
(Some(err_event), Some(ret_event)) => quote_spanned!(block.span()=>
async move {
match async move #block.await {
#[allow(clippy::unit_arg)]
Ok(x) => {
#ret_event;
Ok(x)
},
Err(e) => {
#err_event;
Err(e)
}
}
}
),
(Some(err_event), None) => quote_spanned!(block.span()=>
async move {
match async move #block.await {
#[allow(clippy::unit_arg)]
Ok(x) => Ok(x),
Err(e) => {
#err_event;
Err(e)
}
}
}
),
(None, Some(ret_event)) => quote_spanned!(block.span()=>
async move {
let x = async move #block.await;
#ret_event;
x
}
),
(None, None) => quote_spanned!(block.span()=>
async move #block
),
};
return quote!(
let __tracing_attr_span = #span;
let __tracing_instrument_future = #mk_fut;
if !__tracing_attr_span.is_disabled() {
#follows_from
tracing::Instrument::instrument(
__tracing_instrument_future,
__tracing_attr_span
)
.await
} else {
__tracing_instrument_future.await
}
);
}
let span = quote!(
// These variables are left uninitialized and initialized only
// if the tracing level is statically enabled at this point.
// While the tracing level is also checked at span creation
// time, that will still create a dummy span, and a dummy guard
// and drop the dummy guard later. By lazily initializing these
// variables, Rust will generate a drop flag for them and thus
// only drop the guard if it was created. This creates code that
// is very straightforward for LLVM to optimize out if the tracing
// level is statically disabled, while not causing any performance
// regression in case the level is enabled.
let __tracing_attr_span;
let __tracing_attr_guard;
if tracing::level_enabled!(#level) || tracing::if_log_enabled!(#level, {true} else {false}) {
__tracing_attr_span = #span;
#follows_from
__tracing_attr_guard = __tracing_attr_span.enter();
}
);
match (err_event, ret_event) {
(Some(err_event), Some(ret_event)) => quote_spanned! {block.span()=>
#span
#[allow(clippy::redundant_closure_call)]
match (move || #block)() {
#[allow(clippy::unit_arg)]
Ok(x) => {
#ret_event;
Ok(x)
},
Err(e) => {
#err_event;
Err(e)
}
}
},
(Some(err_event), None) => quote_spanned!(block.span()=>
#span
#[allow(clippy::redundant_closure_call)]
match (move || #block)() {
#[allow(clippy::unit_arg)]
Ok(x) => Ok(x),
Err(e) => {
#err_event;
Err(e)
}
}
),
(None, Some(ret_event)) => quote_spanned!(block.span()=>
#span
#[allow(clippy::redundant_closure_call)]
let x = (move || #block)();
#ret_event;
x
),
(None, None) => quote_spanned!(block.span() =>
// Because `quote` produces a stream of tokens _without_ whitespace, the
// `if` and the block will appear directly next to each other. This
// generates a clippy lint about suspicious `if/else` formatting.
// Therefore, suppress the lint inside the generated code...
#[allow(clippy::suspicious_else_formatting)]
{
#span
// ...but turn the lint back on inside the function body.
#[warn(clippy::suspicious_else_formatting)]
#block
}
),
}
}
/// Indicates whether a field should be recorded as `Value` or `Debug`.
enum RecordType {
/// The field should be recorded using its `Value` implementation.
Value,
/// The field should be recorded using `tracing::field::debug()`.
Debug,
}
impl RecordType {
/// Array of primitive types which should be recorded as [RecordType::Value].
const TYPES_FOR_VALUE: &'static [&'static str] = &[
"bool",
"str",
"u8",
"i8",
"u16",
"i16",
"u32",
"i32",
"u64",
"i64",
"f32",
"f64",
"usize",
"isize",
"NonZeroU8",
"NonZeroI8",
"NonZeroU16",
"NonZeroI16",
"NonZeroU32",
"NonZeroI32",
"NonZeroU64",
"NonZeroI64",
"NonZeroUsize",
"NonZeroIsize",
"Wrapping",
];
/// Parse `RecordType` from [Type] by looking up
/// the [RecordType::TYPES_FOR_VALUE] array.
fn parse_from_ty(ty: &Type) -> Self {
match ty {
Type::Path(TypePath { path, .. })
if path
.segments
.iter()
.last()
.map(|path_segment| {
let ident = path_segment.ident.to_string();
Self::TYPES_FOR_VALUE.iter().any(|&t| t == ident)
})
.unwrap_or(false) =>
{
RecordType::Value
}
Type::Reference(syn::TypeReference { elem, .. }) => RecordType::parse_from_ty(elem),
_ => RecordType::Debug,
}
}
}
fn param_names(pat: Pat, record_type: RecordType) -> Box<dyn Iterator<Item = (Ident, RecordType)>> {
match pat {
Pat::Ident(PatIdent { ident, .. }) => Box::new(iter::once((ident, record_type))),
Pat::Reference(PatReference { pat, .. }) => param_names(*pat, record_type),
// We can't get the concrete type of fields in the struct/tuple
// patterns by using `syn`. e.g. `fn foo(Foo { x, y }: Foo) {}`.
// Therefore, the struct/tuple patterns in the arguments will just
// always be recorded as `RecordType::Debug`.
Pat::Struct(PatStruct { fields, .. }) => Box::new(
fields
.into_iter()
.flat_map(|FieldPat { pat, .. }| param_names(*pat, RecordType::Debug)),
),
Pat::Tuple(PatTuple { elems, .. }) => Box::new(
elems
.into_iter()
.flat_map(|p| param_names(p, RecordType::Debug)),
),
Pat::TupleStruct(PatTupleStruct { elems, .. }) => Box::new(
elems
.into_iter()
.flat_map(|p| param_names(p, RecordType::Debug)),
),
// The above *should* cover all cases of irrefutable patterns,
// but we purposefully don't do any funny business here
// (such as panicking) because that would obscure rustc's
// much more informative error message.
_ => Box::new(iter::empty()),
}
}
/// The specific async code pattern that was detected
enum AsyncKind<'a> {
/// Immediately-invoked async fn, as generated by `async-trait <= 0.1.43`:
/// `async fn foo<...>(...) {...}; Box::pin(foo<...>(...))`
Function(&'a ItemFn),
/// A function returning an async (move) block, optionally `Box::pin`-ed,
/// as generated by `async-trait >= 0.1.44`:
/// `Box::pin(async move { ... })`
Async {
async_expr: &'a ExprAsync,
pinned_box: bool,
},
}
pub(crate) struct AsyncInfo<'block> {
// statement that must be patched
source_stmt: &'block Stmt,
kind: AsyncKind<'block>,
self_type: Option<TypePath>,
input: &'block ItemFn,
}
impl<'block> AsyncInfo<'block> {
/// Get the AST of the inner function we need to hook, if it looks like a
/// manual future implementation.
///
/// When we are given a function that returns a (pinned) future containing the
/// user logic, it is that (pinned) future that needs to be instrumented.
/// Were we to instrument its parent, we would only collect information
/// regarding the allocation of that future, and not its own span of execution.
///
/// We inspect the block of the function to find if it matches any of the
/// following patterns:
///
/// - Immediately-invoked async fn, as generated by `async-trait <= 0.1.43`:
/// `async fn foo<...>(...) {...}; Box::pin(foo<...>(...))`
///
/// - A function returning an async (move) block, optionally `Box::pin`-ed,
/// as generated by `async-trait >= 0.1.44`:
/// `Box::pin(async move { ... })`
///
/// We the return the statement that must be instrumented, along with some
/// other information.
/// 'gen_body' will then be able to use that information to instrument the
/// proper function/future.
///
/// (this follows the approach suggested in
/// https://github.com/dtolnay/async-trait/issues/45#issuecomment-571245673)
pub(crate) fn from_fn(input: &'block ItemFn) -> Option<Self> {
// are we in an async context? If yes, this isn't a manual async-like pattern
if input.sig.asyncness.is_some() {
return None;
}
let block = &input.block;
// list of async functions declared inside the block
let inside_funs = block.stmts.iter().filter_map(|stmt| {
if let Stmt::Item(Item::Fn(fun)) = &stmt {
// If the function is async, this is a candidate
if fun.sig.asyncness.is_some() {
return Some((stmt, fun));
}
}
None
});
// last expression of the block: it determines the return value of the
// block, this is quite likely a `Box::pin` statement or an async block
let (last_expr_stmt, last_expr) = block.stmts.iter().rev().find_map(|stmt| {
if let Stmt::Expr(expr, _semi) = stmt {
Some((stmt, expr))
} else {
None
}
})?;
// is the last expression an async block?
if let Expr::Async(async_expr) = last_expr {
return Some(AsyncInfo {
source_stmt: last_expr_stmt,
kind: AsyncKind::Async {
async_expr,
pinned_box: false,
},
self_type: None,
input,
});
}
// is the last expression a function call?
let (outside_func, outside_args) = match last_expr {
Expr::Call(ExprCall { func, args, .. }) => (func, args),
_ => return None,
};
// is it a call to `Box::pin()`?
let path = match outside_func.as_ref() {
Expr::Path(path) => &path.path,
_ => return None,
};
if !path_to_string(path).ends_with("Box::pin") {
return None;
}
// Does the call take an argument? If it doesn't,
// it's not gonna compile anyway, but that's no reason
// to (try to) perform an out of bounds access
if outside_args.is_empty() {
return None;
}
// Is the argument to Box::pin an async block that
// captures its arguments?
if let Expr::Async(async_expr) = &outside_args[0] {
return Some(AsyncInfo {
source_stmt: last_expr_stmt,
kind: AsyncKind::Async {
async_expr,
pinned_box: true,
},
self_type: None,
input,
});
}
// Is the argument to Box::pin a function call itself?
let func = match &outside_args[0] {
Expr::Call(ExprCall { func, .. }) => func,
_ => return None,
};
// "stringify" the path of the function called
let func_name = match **func {
Expr::Path(ref func_path) => path_to_string(&func_path.path),
_ => return None,
};
// Was that function defined inside of the current block?
// If so, retrieve the statement where it was declared and the function itself
let (stmt_func_declaration, func) = inside_funs
.into_iter()
.find(|(_, fun)| fun.sig.ident == func_name)?;
// If "_self" is present as an argument, we store its type to be able to rewrite "Self" (the
// parameter type) with the type of "_self"
let mut self_type = None;
for arg in &func.sig.inputs {
if let FnArg::Typed(ty) = arg {
if let Pat::Ident(PatIdent { ref ident, .. }) = *ty.pat {
if ident == "_self" {
let mut ty = *ty.ty.clone();
// extract the inner type if the argument is "&self" or "&mut self"
if let Type::Reference(syn::TypeReference { elem, .. }) = ty {
ty = *elem;
}
if let Type::Path(tp) = ty {
self_type = Some(tp);
break;
}
}
}
}
}
Some(AsyncInfo {
source_stmt: stmt_func_declaration,
kind: AsyncKind::Function(func),
self_type,
input,
})
}
pub(crate) fn gen_async(
self,
args: InstrumentArgs,
instrumented_function_name: &str,
) -> Result<proc_macro::TokenStream, syn::Error> {
// let's rewrite some statements!
let mut out_stmts: Vec<TokenStream> = self
.input
.block
.stmts
.iter()
.map(|stmt| stmt.to_token_stream())
.collect();
if let Some((iter, _stmt)) = self
.input
.block
.stmts
.iter()
.enumerate()
.find(|(_iter, stmt)| *stmt == self.source_stmt)
{
// instrument the future by rewriting the corresponding statement
out_stmts[iter] = match self.kind {
// `Box::pin(immediately_invoked_async_fn())`
AsyncKind::Function(fun) => {
let fun = MaybeItemFn::from(fun.clone());
gen_function(
fun.as_ref(),
args,
instrumented_function_name,
self.self_type.as_ref(),
)
}
// `async move { ... }`, optionally pinned
AsyncKind::Async {
async_expr,
pinned_box,
} => {
let instrumented_block = gen_block(
&async_expr.block,
&self.input.sig.inputs,
true,
args,
instrumented_function_name,
None,
);
let async_attrs = &async_expr.attrs;
if pinned_box {
quote! {
Box::pin(#(#async_attrs) * async move { #instrumented_block })
}
} else {
quote! {
#(#async_attrs) * async move { #instrumented_block }
}
}
}
};
}
let vis = &self.input.vis;
let sig = &self.input.sig;
let attrs = &self.input.attrs;
Ok(quote!(
#(#attrs) *
#vis #sig {
#(#out_stmts) *
}
)
.into())
}
}
// Return a path as a String
fn path_to_string(path: &Path) -> String {
use std::fmt::Write;
// some heuristic to prevent too many allocations
let mut res = String::with_capacity(path.segments.len() * 5);
for i in 0..path.segments.len() {
write!(&mut res, "{}", path.segments[i].ident)
.expect("writing to a String should never fail");
if i < path.segments.len() - 1 {
res.push_str("::");
}
}
res
}
/// A visitor struct to replace idents and types in some piece
/// of code (e.g. the "self" and "Self" tokens in user-supplied
/// fields expressions when the function is generated by an old
/// version of async-trait).
struct IdentAndTypesRenamer<'a> {
types: Vec<(&'a str, TypePath)>,
idents: Vec<(Ident, Ident)>,
}
impl<'a> VisitMut for IdentAndTypesRenamer<'a> {
// we deliberately compare strings because we want to ignore the spans
// If we apply clippy's lint, the behavior changes
#[allow(clippy::cmp_owned)]
fn visit_ident_mut(&mut self, id: &mut Ident) {
for (old_ident, new_ident) in &self.idents {
if id.to_string() == old_ident.to_string() {
*id = new_ident.clone();
}
}
}
fn visit_type_mut(&mut self, ty: &mut Type) {
for (type_name, new_type) in &self.types {
if let Type::Path(TypePath { path, .. }) = ty {
if path_to_string(path) == *type_name {
*ty = Type::Path(new_type.clone());
}
}
}
}
}
// A visitor struct that replace an async block by its patched version
struct AsyncTraitBlockReplacer<'a> {
block: &'a Block,
patched_block: Block,
}
impl<'a> VisitMut for AsyncTraitBlockReplacer<'a> {
fn visit_block_mut(&mut self, i: &mut Block) {
if i == self.block {
*i = self.patched_block.clone();
}
}
}
// Replaces any `impl Trait` with `_` so it can be used as the type in
// a `let` statement's LHS.
struct ImplTraitEraser;
impl VisitMut for ImplTraitEraser {
fn visit_type_mut(&mut self, t: &mut Type) {
if let Type::ImplTrait(..) = t {
*t = syn::TypeInfer {
underscore_token: Token![_](t.span()),
}
.into();
} else {
syn::visit_mut::visit_type_mut(self, t);
}
}
}
fn erase_impl_trait(ty: &Type) -> Type {
let mut ty = ty.clone();
ImplTraitEraser.visit_type_mut(&mut ty);
ty
}