diff --git a/src/librustc_borrowck/borrowck/mod.rs b/src/librustc_borrowck/borrowck/mod.rs index c57cbcb929fbc..db947a27472ad 100644 --- a/src/librustc_borrowck/borrowck/mod.rs +++ b/src/librustc_borrowck/borrowck/mod.rs @@ -522,6 +522,16 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> { } pub fn report(&self, err: BckError<'tcx>) { + // Catch and handle some particular cases. + match (&err.code, &err.cause) { + (&err_out_of_scope(ty::ReScope(_), ty::ReStatic), &euv::ClosureCapture(span)) | + (&err_out_of_scope(ty::ReScope(_), ty::ReFree(..)), &euv::ClosureCapture(span)) => { + return self.report_out_of_scope_escaping_closure_capture(&err, span); + } + _ => { } + } + + // General fallback. self.span_err( err.span, &self.bckerr_to_string(&err)); @@ -796,16 +806,10 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> { format!("{} does not live long enough", msg) } err_borrowed_pointer_too_short(..) => { - let descr = match opt_loan_path(&err.cmt) { - Some(lp) => { - format!("`{}`", self.loan_path_to_string(&*lp)) - } - None => self.cmt_to_string(&*err.cmt), - }; - + let descr = self.cmt_to_path_or_string(&err.cmt); format!("lifetime of {} is too short to guarantee \ - its contents can be safely reborrowed", - descr) + its contents can be safely reborrowed", + descr) } } } @@ -888,6 +892,39 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> { } } + fn report_out_of_scope_escaping_closure_capture(&self, + err: &BckError<'tcx>, + capture_span: Span) + { + let cmt_path_or_string = self.cmt_to_path_or_string(&err.cmt); + + span_err!( + self.tcx.sess, err.span, E0373, + "closure may outlive the current function, \ + but it borrows {}, \ + which is owned by the current function", + cmt_path_or_string); + + self.tcx.sess.span_note( + capture_span, + &format!("{} is borrowed here", + cmt_path_or_string)); + + let suggestion = + match self.tcx.sess.codemap().span_to_snippet(err.span) { + Ok(string) => format!("move {}", string), + Err(_) => format!("move || ") + }; + + self.tcx.sess.span_suggestion( + err.span, + &format!("to force the closure to take ownership of {} \ + (and any other referenced variables), \ + use the `move` keyword, as shown:", + cmt_path_or_string), + suggestion); + } + pub fn note_and_explain_bckerr(&self, err: BckError<'tcx>) { let code = err.code; match code { @@ -1035,6 +1072,13 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> { pub fn cmt_to_string(&self, cmt: &mc::cmt_<'tcx>) -> String { cmt.descriptive_string(self.tcx) } + + pub fn cmt_to_path_or_string(&self, cmt: &mc::cmt<'tcx>) -> String { + match opt_loan_path(cmt) { + Some(lp) => format!("`{}`", self.loan_path_to_string(&lp)), + None => self.cmt_to_string(cmt), + } + } } fn is_statement_scope(tcx: &ty::ctxt, region: ty::Region) -> bool { diff --git a/src/librustc_borrowck/diagnostics.rs b/src/librustc_borrowck/diagnostics.rs new file mode 100644 index 0000000000000..981b28593f9a4 --- /dev/null +++ b/src/librustc_borrowck/diagnostics.rs @@ -0,0 +1,17 @@ +// Copyright 2014 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. + +#![allow(non_snake_case)] + +register_diagnostics! { + E0373 // closure may outlive current fn, but it borrows {}, which is owned by current fn +} + +__build_diagnostic_array! { DIAGNOSTICS } diff --git a/src/librustc_borrowck/lib.rs b/src/librustc_borrowck/lib.rs index 54feed930a80d..647ea3555ba91 100644 --- a/src/librustc_borrowck/lib.rs +++ b/src/librustc_borrowck/lib.rs @@ -40,6 +40,10 @@ pub use borrowck::check_crate; pub use borrowck::build_borrowck_dataflow_data_for_fn; pub use borrowck::FnPartsWithCFG; +// NB: This module needs to be declared first so diagnostics are +// registered before they are used. +pub mod diagnostics; + mod borrowck; pub mod graphviz; diff --git a/src/test/compile-fail/borrowck-escaping-closure-error-1.rs b/src/test/compile-fail/borrowck-escaping-closure-error-1.rs new file mode 100644 index 0000000000000..87e40df7663ba --- /dev/null +++ b/src/test/compile-fail/borrowck-escaping-closure-error-1.rs @@ -0,0 +1,25 @@ +// Copyright 2015 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. + +use std::thread::spawn; + +// Test that we give a custom error (E0373) for the case where a +// closure is escaping current frame, and offer a suggested code edit. +// I refrained from including the precise message here, but the +// original text as of the time of this writing is: +// +// closure may outlive the current function, but it borrows `books`, +// which is owned by the current function + +fn main() { + let mut books = vec![1,2,3]; + spawn(|| books.push(4)); + //~^ ERROR E0373 +} diff --git a/src/test/compile-fail/borrowck-escaping-closure-error-2.rs b/src/test/compile-fail/borrowck-escaping-closure-error-2.rs new file mode 100644 index 0000000000000..67700be890b1f --- /dev/null +++ b/src/test/compile-fail/borrowck-escaping-closure-error-2.rs @@ -0,0 +1,25 @@ +// Copyright 2015 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. + +// Test that we give a custom error (E0373) for the case where a +// closure is escaping current frame, and offer a suggested code edit. +// I refrained from including the precise message here, but the +// original text as of the time of this writing is: +// +// closure may outlive the current function, but it borrows `books`, +// which is owned by the current function + +fn foo<'a>(x: &'a i32) -> Box { + let mut books = vec![1,2,3]; + Box::new(|| books.push(4)) + //~^ ERROR E0373 +} + +fn main() { } diff --git a/src/test/compile-fail/issue-16747.rs b/src/test/compile-fail/issue-16747.rs index 64334fe4392f8..b4abef0bd280b 100644 --- a/src/test/compile-fail/issue-16747.rs +++ b/src/test/compile-fail/issue-16747.rs @@ -18,10 +18,10 @@ trait Collection { fn len(&self) -> usize; } struct List<'a, T: ListItem<'a>> { //~^ ERROR the parameter type `T` may not live long enough -//~^^ NOTE ...so that the reference type `&'a [T]` does not outlive the data it points at +//~| HELP consider adding an explicit lifetime bound +//~| NOTE ...so that the reference type `&'a [T]` does not outlive the data it points at slice: &'a [T] } -//~^ HELP consider adding an explicit lifetime bound impl<'a, T: ListItem<'a>> Collection for List<'a, T> { fn len(&self) -> usize { 0 diff --git a/src/test/compile-fail/issue-4335.rs b/src/test/compile-fail/issue-4335.rs index 55a793f7480a4..0089bff3e8fd8 100644 --- a/src/test/compile-fail/issue-4335.rs +++ b/src/test/compile-fail/issue-4335.rs @@ -15,7 +15,7 @@ fn id(t: T) -> T { t } fn f<'r, T>(v: &'r T) -> Box T + 'r> { // FIXME (#22405): Replace `Box::new` with `box` here when/if possible. id(Box::new(|| *v)) - //~^ ERROR `v` does not live long enough + //~^ ERROR E0373 //~| ERROR cannot move out of borrowed content } diff --git a/src/test/compile-fail/regions-nested-fns-2.rs b/src/test/compile-fail/regions-nested-fns-2.rs index bdebadb2832ca..948dc8cd21968 100644 --- a/src/test/compile-fail/regions-nested-fns-2.rs +++ b/src/test/compile-fail/regions-nested-fns-2.rs @@ -13,7 +13,7 @@ fn ignore(_f: F) where F: for<'z> FnOnce(&'z isize) -> &'z isize {} fn nested() { let y = 3; ignore( - |z| { //~ ERROR `y` does not live long enough + |z| { //~ ERROR E0373 if false { &y } else { z } }); }