From e1e52eb5a0156839a71c0ffc5424e2160271170e Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Esteban=20K=C3=BCber?= Date: Wed, 17 Oct 2018 21:07:31 -0700 Subject: [PATCH] Suggest appropriate syntax on missing lifetime specifier in return type Suggest using `'static` when a lifetime is missing in the return type with a structured suggestion instead of a note. --- src/librustc/hir/lowering.rs | 2 +- src/librustc/middle/resolve_lifetime.rs | 55 ++++++++++++++++--- ...nd-lifetime-in-binding-only.elision.stderr | 6 +- ...und-lifetime-in-return-only.elision.stderr | 6 +- src/test/ui/foreign-fn-return-lifetime.fixed | 18 ++++++ src/test/ui/foreign-fn-return-lifetime.rs | 6 +- src/test/ui/foreign-fn-return-lifetime.stderr | 10 ++-- src/test/ui/issues/issue-13497.stderr | 6 +- src/test/ui/issues/issue-26638.stderr | 12 ++-- ...urn-type-requires-explicit-lifetime.stderr | 24 +++++--- .../lifetime-elision-return-type-trait.rs | 10 ++++ .../lifetime-elision-return-type-trait.stderr | 19 +++++++ .../underscore-lifetime-binders.stderr | 6 +- 13 files changed, 146 insertions(+), 34 deletions(-) create mode 100644 src/test/ui/foreign-fn-return-lifetime.fixed create mode 100644 src/test/ui/lifetimes/lifetime-elision-return-type-trait.rs create mode 100644 src/test/ui/lifetimes/lifetime-elision-return-type-trait.stderr diff --git a/src/librustc/hir/lowering.rs b/src/librustc/hir/lowering.rs index cce872927b147..04a2308cead34 100644 --- a/src/librustc/hir/lowering.rs +++ b/src/librustc/hir/lowering.rs @@ -1152,7 +1152,7 @@ impl<'a> LoweringContext<'a> { TyKind::Slice(ref ty) => hir::TyKind::Slice(self.lower_ty(ty, itctx)), TyKind::Ptr(ref mt) => hir::TyKind::Ptr(self.lower_mt(mt, itctx)), TyKind::Rptr(ref region, ref mt) => { - let span = t.span.shrink_to_lo(); + let span = self.sess.source_map().next_point(t.span.shrink_to_lo()); let lifetime = match *region { Some(ref lt) => self.lower_lifetime(lt), None => self.elided_ref_lifetime(span), diff --git a/src/librustc/middle/resolve_lifetime.rs b/src/librustc/middle/resolve_lifetime.rs index 98e80d333c1c8..86db74b78b983 100644 --- a/src/librustc/middle/resolve_lifetime.rs +++ b/src/librustc/middle/resolve_lifetime.rs @@ -2238,7 +2238,7 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> { if let Some(params) = error { if lifetime_refs.len() == 1 { - self.report_elision_failure(&mut err, params); + self.report_elision_failure(&mut err, params, span); } } @@ -2249,6 +2249,7 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> { &mut self, db: &mut DiagnosticBuilder<'_>, params: &[ElisionFailureInfo], + span: Span, ) { let mut m = String::new(); let len = params.len(); @@ -2304,7 +2305,29 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> { "this function's return type contains a borrowed value, but \ there is no value for it to be borrowed from" ); - help!(db, "consider giving it a 'static lifetime"); + let msg = "consider giving it a 'static lifetime"; + match self.tcx.sess.source_map().span_to_snippet(span) { + Ok(ref snippet) if snippet == "&" => db.span_suggestion_with_applicability( + span, + msg, + "&'static ".to_owned(), + Applicability::MachineApplicable, + ), + Ok(ref snippet) + if snippet == "'_" => db.span_suggestion_with_applicability( + span, + msg, + "'static".to_owned(), + Applicability::MachineApplicable, + ), + Ok(ref snippet) => db.span_suggestion_with_applicability( + span, + msg, + format!("{} + 'static", snippet), + Applicability::MaybeIncorrect, + ), + Err(_) => db.help(msg), + }; } else if elided_len == 0 { help!( db, @@ -2312,11 +2335,29 @@ impl<'a, 'tcx> LifetimeContext<'a, 'tcx> { an elided lifetime, but the lifetime cannot be derived from \ the arguments" ); - help!( - db, - "consider giving it an explicit bounded or 'static \ - lifetime" - ); + let msg = "consider giving it an explicit bounded or 'static lifetime"; + match self.tcx.sess.source_map().span_to_snippet(span) { + Ok(ref snippet) if snippet == "&" => db.span_suggestion_with_applicability( + span, + msg, + "&'static ".to_owned(), + Applicability::MachineApplicable, + ), + Ok(ref snippet) + if snippet == "'_" => db.span_suggestion_with_applicability( + span, + msg, + "'static".to_owned(), + Applicability::MachineApplicable, + ), + Ok(ref snippet) => db.span_suggestion_with_applicability( + span, + msg, + format!("{} + 'static", snippet), + Applicability::MaybeIncorrect, + ), + Err(_) => db.help(msg), + }; } else if elided_len == 1 { help!( db, diff --git a/src/test/ui/associated-types/bound-lifetime-in-binding-only.elision.stderr b/src/test/ui/associated-types/bound-lifetime-in-binding-only.elision.stderr index 0a12aa76a785b..4336aaf71ba02 100644 --- a/src/test/ui/associated-types/bound-lifetime-in-binding-only.elision.stderr +++ b/src/test/ui/associated-types/bound-lifetime-in-binding-only.elision.stderr @@ -2,10 +2,12 @@ error[E0106]: missing lifetime specifier --> $DIR/bound-lifetime-in-binding-only.rs:62:23 | LL | fn elision &i32>() { - | ^ expected lifetime parameter + | ^ + | | + | expected lifetime parameter + | help: consider giving it a 'static lifetime: `&'static` | = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from - = help: consider giving it a 'static lifetime error: aborting due to previous error diff --git a/src/test/ui/associated-types/bound-lifetime-in-return-only.elision.stderr b/src/test/ui/associated-types/bound-lifetime-in-return-only.elision.stderr index 8fefdfd4d19ef..fbc4df54225d5 100644 --- a/src/test/ui/associated-types/bound-lifetime-in-return-only.elision.stderr +++ b/src/test/ui/associated-types/bound-lifetime-in-return-only.elision.stderr @@ -2,10 +2,12 @@ error[E0106]: missing lifetime specifier --> $DIR/bound-lifetime-in-return-only.rs:44:23 | LL | fn elision(_: fn() -> &i32) { - | ^ expected lifetime parameter + | ^ + | | + | expected lifetime parameter + | help: consider giving it a 'static lifetime: `&'static` | = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from - = help: consider giving it a 'static lifetime error: aborting due to previous error diff --git a/src/test/ui/foreign-fn-return-lifetime.fixed b/src/test/ui/foreign-fn-return-lifetime.fixed new file mode 100644 index 0000000000000..9fc35eae7052f --- /dev/null +++ b/src/test/ui/foreign-fn-return-lifetime.fixed @@ -0,0 +1,18 @@ +// Copyright 2017 The Rust Project Developers. See the COPYRIGHT +// file at the top-level directory of this distribution and at +// http://rust-lang.org/COPYRIGHT. +// +// Licensed under the Apache License, Version 2.0 or the MIT license +// , at your +// option. This file may not be copied, modified, or distributed +// except according to those terms. + +// run-rustfix + +extern "C" { + pub fn g(_: &u8) -> &u8; // OK + pub fn f() -> &'static u8; //~ ERROR missing lifetime specifier +} + +fn main() {} diff --git a/src/test/ui/foreign-fn-return-lifetime.rs b/src/test/ui/foreign-fn-return-lifetime.rs index da77066150cc7..941e7e05a3635 100644 --- a/src/test/ui/foreign-fn-return-lifetime.rs +++ b/src/test/ui/foreign-fn-return-lifetime.rs @@ -8,9 +8,11 @@ // option. This file may not be copied, modified, or distributed // except according to those terms. +// run-rustfix + extern "C" { - fn g(_: &u8) -> &u8; // OK - fn f() -> &u8; //~ ERROR missing lifetime specifier + pub fn g(_: &u8) -> &u8; // OK + pub fn f() -> &u8; //~ ERROR missing lifetime specifier } fn main() {} diff --git a/src/test/ui/foreign-fn-return-lifetime.stderr b/src/test/ui/foreign-fn-return-lifetime.stderr index ea15897b3d694..4e52d6044c4e9 100644 --- a/src/test/ui/foreign-fn-return-lifetime.stderr +++ b/src/test/ui/foreign-fn-return-lifetime.stderr @@ -1,11 +1,13 @@ error[E0106]: missing lifetime specifier - --> $DIR/foreign-fn-return-lifetime.rs:13:15 + --> $DIR/foreign-fn-return-lifetime.rs:15:19 | -LL | fn f() -> &u8; //~ ERROR missing lifetime specifier - | ^ expected lifetime parameter +LL | pub fn f() -> &u8; //~ ERROR missing lifetime specifier + | ^ + | | + | expected lifetime parameter + | help: consider giving it a 'static lifetime: `&'static` | = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from - = help: consider giving it a 'static lifetime error: aborting due to previous error diff --git a/src/test/ui/issues/issue-13497.stderr b/src/test/ui/issues/issue-13497.stderr index ab6d041bd48d7..88b6a831d7e41 100644 --- a/src/test/ui/issues/issue-13497.stderr +++ b/src/test/ui/issues/issue-13497.stderr @@ -2,10 +2,12 @@ error[E0106]: missing lifetime specifier --> $DIR/issue-13497.rs:12:5 | LL | &str //~ ERROR missing lifetime specifier - | ^ expected lifetime parameter + | ^ + | | + | expected lifetime parameter + | help: consider giving it a 'static lifetime: `&'static` | = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from - = help: consider giving it a 'static lifetime error: aborting due to previous error diff --git a/src/test/ui/issues/issue-26638.stderr b/src/test/ui/issues/issue-26638.stderr index cf6fcd9f01cc8..e4464b2dd313d 100644 --- a/src/test/ui/issues/issue-26638.stderr +++ b/src/test/ui/issues/issue-26638.stderr @@ -10,19 +10,23 @@ error[E0106]: missing lifetime specifier --> $DIR/issue-26638.rs:14:40 | LL | fn parse_type_2(iter: fn(&u8)->&u8) -> &str { iter() } - | ^ expected lifetime parameter + | ^ + | | + | expected lifetime parameter + | help: consider giving it an explicit bounded or 'static lifetime: `&'static` | = help: this function's return type contains a borrowed value with an elided lifetime, but the lifetime cannot be derived from the arguments - = help: consider giving it an explicit bounded or 'static lifetime error[E0106]: missing lifetime specifier --> $DIR/issue-26638.rs:17:22 | LL | fn parse_type_3() -> &str { unimplemented!() } - | ^ expected lifetime parameter + | ^ + | | + | expected lifetime parameter + | help: consider giving it a 'static lifetime: `&'static` | = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from - = help: consider giving it a 'static lifetime error: aborting due to 3 previous errors diff --git a/src/test/ui/lifetimes/lifetime-elision-return-type-requires-explicit-lifetime.stderr b/src/test/ui/lifetimes/lifetime-elision-return-type-requires-explicit-lifetime.stderr index 30cff86ed1d40..9962dbc9812bd 100644 --- a/src/test/ui/lifetimes/lifetime-elision-return-type-requires-explicit-lifetime.stderr +++ b/src/test/ui/lifetimes/lifetime-elision-return-type-requires-explicit-lifetime.stderr @@ -2,10 +2,12 @@ error[E0106]: missing lifetime specifier --> $DIR/lifetime-elision-return-type-requires-explicit-lifetime.rs:12:11 | LL | fn f() -> &isize { //~ ERROR missing lifetime specifier - | ^ expected lifetime parameter + | ^ + | | + | expected lifetime parameter + | help: consider giving it a 'static lifetime: `&'static` | = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from - = help: consider giving it a 'static lifetime error[E0106]: missing lifetime specifier --> $DIR/lifetime-elision-return-type-requires-explicit-lifetime.rs:17:33 @@ -27,28 +29,34 @@ error[E0106]: missing lifetime specifier --> $DIR/lifetime-elision-return-type-requires-explicit-lifetime.rs:31:20 | LL | fn i(_x: isize) -> &isize { //~ ERROR missing lifetime specifier - | ^ expected lifetime parameter + | ^ + | | + | expected lifetime parameter + | help: consider giving it an explicit bounded or 'static lifetime: `&'static` | = help: this function's return type contains a borrowed value with an elided lifetime, but the lifetime cannot be derived from the arguments - = help: consider giving it an explicit bounded or 'static lifetime error[E0106]: missing lifetime specifier --> $DIR/lifetime-elision-return-type-requires-explicit-lifetime.rs:44:24 | LL | fn j(_x: StaticStr) -> &isize { //~ ERROR missing lifetime specifier - | ^ expected lifetime parameter + | ^ + | | + | expected lifetime parameter + | help: consider giving it an explicit bounded or 'static lifetime: `&'static` | = help: this function's return type contains a borrowed value with an elided lifetime, but the lifetime cannot be derived from the arguments - = help: consider giving it an explicit bounded or 'static lifetime error[E0106]: missing lifetime specifier --> $DIR/lifetime-elision-return-type-requires-explicit-lifetime.rs:50:49 | LL | fn k<'a, T: WithLifetime<'a>>(_x: T::Output) -> &isize { - | ^ expected lifetime parameter + | ^ + | | + | expected lifetime parameter + | help: consider giving it an explicit bounded or 'static lifetime: `&'static` | = help: this function's return type contains a borrowed value with an elided lifetime, but the lifetime cannot be derived from the arguments - = help: consider giving it an explicit bounded or 'static lifetime error: aborting due to 6 previous errors diff --git a/src/test/ui/lifetimes/lifetime-elision-return-type-trait.rs b/src/test/ui/lifetimes/lifetime-elision-return-type-trait.rs new file mode 100644 index 0000000000000..6b6e263b7fd1a --- /dev/null +++ b/src/test/ui/lifetimes/lifetime-elision-return-type-trait.rs @@ -0,0 +1,10 @@ +trait Future { + type Item; + type Error; +} + +use std::error::Error; + +fn foo() -> impl Future> { + Ok(()) +} diff --git a/src/test/ui/lifetimes/lifetime-elision-return-type-trait.stderr b/src/test/ui/lifetimes/lifetime-elision-return-type-trait.stderr new file mode 100644 index 0000000000000..426941b949daa --- /dev/null +++ b/src/test/ui/lifetimes/lifetime-elision-return-type-trait.stderr @@ -0,0 +1,19 @@ +error[E0601]: `main` function not found in crate `lifetime_elision_return_type_trait` + | + = note: consider adding a `main` function to `$DIR/lifetime-elision-return-type-trait.rs` + +error[E0106]: missing lifetime specifier + --> $DIR/lifetime-elision-return-type-trait.rs:8:44 + | +LL | fn foo() -> impl Future> { + | ^^^^^ + | | + | expected lifetime parameter + | help: consider giving it a 'static lifetime: `Error + 'static` + | + = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from + +error: aborting due to 2 previous errors + +Some errors occurred: E0106, E0601. +For more information about an error, try `rustc --explain E0106`. diff --git a/src/test/ui/underscore-lifetime/underscore-lifetime-binders.stderr b/src/test/ui/underscore-lifetime/underscore-lifetime-binders.stderr index fc9f3e642d402..b0da67a7c346e 100644 --- a/src/test/ui/underscore-lifetime/underscore-lifetime-binders.stderr +++ b/src/test/ui/underscore-lifetime/underscore-lifetime-binders.stderr @@ -26,10 +26,12 @@ error[E0106]: missing lifetime specifier --> $DIR/underscore-lifetime-binders.rs:24:29 | LL | fn meh() -> Box Meh<'_>> //~ ERROR cannot be used here - | ^^ expected lifetime parameter + | ^^ + | | + | expected lifetime parameter + | help: consider giving it a 'static lifetime: `'static` | = help: this function's return type contains a borrowed value, but there is no value for it to be borrowed from - = help: consider giving it a 'static lifetime error[E0106]: missing lifetime specifier --> $DIR/underscore-lifetime-binders.rs:30:35