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Better errors when rustc cannot derive lifetimes

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This commit is contained in:
Jack Fransham 2015-11-29 14:23:16 +00:00
parent 323781cdf7
commit a1a48c42b6
1 changed files with 14 additions and 1 deletions
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15
src/librustc_typeck/astconv.rs
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@ -203,11 +203,15 @@ fn report_elision_failure(
{
let mut m = String::new();
let len = params.len();
let mut any_lifetimes = false;
for (i, info) in params.into_iter().enumerate() {
let ElisionFailureInfo {
name, lifetime_count: n, have_bound_regions
} = info;
any_lifetimes = any_lifetimes || (n > 0);
let help_name = if name.is_empty() {
format!("argument {}", i + 1)
} else {
@ -229,7 +233,16 @@ fn report_elision_failure(
m.push_str(", ");
}
}
if len == 1 {
if !any_lifetimes {
fileline_help!(tcx.sess, default_span,
"this function's return type contains a borrowed value with \
an elided lifetime, but the lifetime cannot be derived from \
the arguments");
fileline_help!(tcx.sess, default_span,
"consider giving it an explicit bounded or 'static \
lifetime");
} else if len == 1 {
fileline_help!(tcx.sess, default_span,
"this function's return type contains a borrowed value, but \
the signature does not say which {} it is borrowed from",