diff --git a/tracing-attributes/Cargo.toml b/tracing-attributes/Cargo.toml index 5d8915331f..abce8a5195 100644 --- a/tracing-attributes/Cargo.toml +++ b/tracing-attributes/Cargo.toml @@ -50,6 +50,8 @@ tracing-subscriber = { path = "../tracing-subscriber", version = "0.3.0", featur tokio-test = { version = "0.3.0" } tracing-core = { path = "../tracing-core", version = "0.1.28"} async-trait = "0.1.56" +trybuild = "1.0.64" +rustversion = "1.0.9" [badges] maintenance = { status = "experimental" } diff --git a/tracing-attributes/src/expand.rs b/tracing-attributes/src/expand.rs index 7e385566c4..70204395ea 100644 --- a/tracing-attributes/src/expand.rs +++ b/tracing-attributes/src/expand.rs @@ -2,10 +2,11 @@ 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, Signature, Stmt, Token, TypePath, + Path, ReturnType, Signature, Stmt, Token, Type, TypePath, }; use crate::{ @@ -18,7 +19,7 @@ pub(crate) fn gen_function<'a, B: ToTokens + 'a>( input: MaybeItemFnRef<'a, B>, args: InstrumentArgs, instrumented_function_name: &str, - self_type: Option<&syn::TypePath>, + 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 @@ -31,7 +32,7 @@ pub(crate) fn gen_function<'a, B: ToTokens + 'a>( } = input; let Signature { - output: return_type, + output, inputs: params, unsafety, asyncness, @@ -49,8 +50,35 @@ pub(crate) fn gen_function<'a, B: ToTokens + 'a>( 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(unreachable_code, clippy::diverging_sub_expression, clippy::let_unit_value)] + if false { + let __tracing_attr_fake_return: #return_type = + unreachable!("this is just for type inference, and is unreachable code"); + return __tracing_attr_fake_return; + } + }; + let block = quote! { + { + #fake_return_edge + #block + } + }; + let body = gen_block( - block, + &block, params, asyncness.is_some(), args, @@ -60,7 +88,7 @@ pub(crate) fn gen_function<'a, B: ToTokens + 'a>( quote!( #(#attrs) * - #vis #constness #unsafety #asyncness #abi fn #ident<#gen_params>(#params) #return_type + #vis #constness #unsafety #asyncness #abi fn #ident<#gen_params>(#params) #output #where_clause { #warnings @@ -76,7 +104,7 @@ fn gen_block( async_context: bool, mut args: InstrumentArgs, instrumented_function_name: &str, - self_type: Option<&syn::TypePath>, + self_type: Option<&TypePath>, ) -> proc_macro2::TokenStream { // generate the span's name let span_name = args @@ -393,11 +421,11 @@ impl RecordType { "Wrapping", ]; - /// Parse `RecordType` from [syn::Type] by looking up + /// Parse `RecordType` from [Type] by looking up /// the [RecordType::TYPES_FOR_VALUE] array. - fn parse_from_ty(ty: &syn::Type) -> Self { + fn parse_from_ty(ty: &Type) -> Self { match ty { - syn::Type::Path(syn::TypePath { path, .. }) + Type::Path(TypePath { path, .. }) if path .segments .iter() @@ -410,9 +438,7 @@ impl RecordType { { RecordType::Value } - syn::Type::Reference(syn::TypeReference { elem, .. }) => { - RecordType::parse_from_ty(elem) - } + Type::Reference(syn::TypeReference { elem, .. }) => RecordType::parse_from_ty(elem), _ => RecordType::Debug, } } @@ -471,7 +497,7 @@ pub(crate) struct AsyncInfo<'block> { // statement that must be patched source_stmt: &'block Stmt, kind: AsyncKind<'block>, - self_type: Option, + self_type: Option, input: &'block ItemFn, } @@ -606,11 +632,11 @@ impl<'block> AsyncInfo<'block> { if ident == "_self" { let mut ty = *ty.ty.clone(); // extract the inner type if the argument is "&self" or "&mut self" - if let syn::Type::Reference(syn::TypeReference { elem, .. }) = ty { + if let Type::Reference(syn::TypeReference { elem, .. }) = ty { ty = *elem; } - if let syn::Type::Path(tp) = ty { + if let Type::Path(tp) = ty { self_type = Some(tp); break; } @@ -722,7 +748,7 @@ struct IdentAndTypesRenamer<'a> { idents: Vec<(Ident, Ident)>, } -impl<'a> syn::visit_mut::VisitMut for IdentAndTypesRenamer<'a> { +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)] @@ -734,11 +760,11 @@ impl<'a> syn::visit_mut::VisitMut for IdentAndTypesRenamer<'a> { } } - fn visit_type_mut(&mut self, ty: &mut syn::Type) { + fn visit_type_mut(&mut self, ty: &mut Type) { for (type_name, new_type) in &self.types { - if let syn::Type::Path(TypePath { path, .. }) = ty { + if let Type::Path(TypePath { path, .. }) = ty { if path_to_string(path) == *type_name { - *ty = syn::Type::Path(new_type.clone()); + *ty = Type::Path(new_type.clone()); } } } @@ -751,10 +777,33 @@ struct AsyncTraitBlockReplacer<'a> { patched_block: Block, } -impl<'a> syn::visit_mut::VisitMut for AsyncTraitBlockReplacer<'a> { +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 +} diff --git a/tracing-attributes/tests/ui.rs b/tracing-attributes/tests/ui.rs new file mode 100644 index 0000000000..f11cc019eb --- /dev/null +++ b/tracing-attributes/tests/ui.rs @@ -0,0 +1,7 @@ +// Only test on nightly, since UI tests are bound to change over time +#[rustversion::stable] +#[test] +fn async_instrument() { + let t = trybuild::TestCases::new(); + t.compile_fail("tests/ui/async_instrument.rs"); +} diff --git a/tracing-attributes/tests/ui/async_instrument.rs b/tracing-attributes/tests/ui/async_instrument.rs new file mode 100644 index 0000000000..5b245746a6 --- /dev/null +++ b/tracing-attributes/tests/ui/async_instrument.rs @@ -0,0 +1,46 @@ +#![allow(unreachable_code)] + +#[tracing::instrument] +async fn unit() { + "" +} + +#[tracing::instrument] +async fn simple_mismatch() -> String { + "" +} + +// FIXME: this span is still pretty poor +#[tracing::instrument] +async fn opaque_unsatisfied() -> impl std::fmt::Display { + ("",) +} + +struct Wrapper(T); + +#[tracing::instrument] +async fn mismatch_with_opaque() -> Wrapper { + "" +} + +#[tracing::instrument] +async fn early_return_unit() { + if true { + return ""; + } +} + +#[tracing::instrument] +async fn early_return() -> String { + if true { + return ""; + } + String::new() +} + +#[tracing::instrument] +async fn extra_semicolon() -> i32 { + 1; +} + +fn main() {} diff --git a/tracing-attributes/tests/ui/async_instrument.stderr b/tracing-attributes/tests/ui/async_instrument.stderr new file mode 100644 index 0000000000..5214f92a7e --- /dev/null +++ b/tracing-attributes/tests/ui/async_instrument.stderr @@ -0,0 +1,89 @@ +error[E0308]: mismatched types + --> tests/ui/async_instrument.rs:5:5 + | +5 | "" + | ^^ expected `()`, found `&str` + | +note: return type inferred to be `()` here + --> tests/ui/async_instrument.rs:4:10 + | +4 | async fn unit() { + | ^^^^ + +error[E0308]: mismatched types + --> tests/ui/async_instrument.rs:10:5 + | +10 | "" + | ^^- help: try using a conversion method: `.to_string()` + | | + | expected struct `String`, found `&str` + | +note: return type inferred to be `String` here + --> tests/ui/async_instrument.rs:9:31 + | +9 | async fn simple_mismatch() -> String { + | ^^^^^^ + +error[E0277]: `(&str,)` doesn't implement `std::fmt::Display` + --> tests/ui/async_instrument.rs:14:1 + | +14 | #[tracing::instrument] + | ^^^^^^^^^^^^^^^^^^^^^^ `(&str,)` cannot be formatted with the default formatter + | + = help: the trait `std::fmt::Display` is not implemented for `(&str,)` + = note: in format strings you may be able to use `{:?}` (or {:#?} for pretty-print) instead + = note: this error originates in the attribute macro `tracing::instrument` (in Nightly builds, run with -Z macro-backtrace for more info) + +error[E0308]: mismatched types + --> tests/ui/async_instrument.rs:23:5 + | +23 | "" + | ^^ expected struct `Wrapper`, found `&str` + | + = note: expected struct `Wrapper<_>` + found reference `&'static str` +note: return type inferred to be `Wrapper<_>` here + --> tests/ui/async_instrument.rs:22:36 + | +22 | async fn mismatch_with_opaque() -> Wrapper { + | ^^^^^^^ +help: try wrapping the expression in `Wrapper` + | +23 | Wrapper("") + | ++++++++ + + +error[E0308]: mismatched types + --> tests/ui/async_instrument.rs:29:16 + | +29 | return ""; + | ^^ expected `()`, found `&str` + | +note: return type inferred to be `()` here + --> tests/ui/async_instrument.rs:27:10 + | +27 | async fn early_return_unit() { + | ^^^^^^^^^^^^^^^^^ + +error[E0308]: mismatched types + --> tests/ui/async_instrument.rs:36:16 + | +36 | return ""; + | ^^- help: try using a conversion method: `.to_string()` + | | + | expected struct `String`, found `&str` + | +note: return type inferred to be `String` here + --> tests/ui/async_instrument.rs:34:28 + | +34 | async fn early_return() -> String { + | ^^^^^^ + +error[E0308]: mismatched types + --> tests/ui/async_instrument.rs:42:35 + | +42 | async fn extra_semicolon() -> i32 { + | ___________________________________^ +43 | | 1; + | | - help: remove this semicolon +44 | | } + | |_^ expected `i32`, found `()`