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in which the fn-must-use codepath is prevented from panicking on closure

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The must-use lint needs the DefId of called functions and method
receivers in order to look for a `#[must_use]` attribute, but this would
ICE (!) if a called function was actually a closure (with a non-unit
return value). Instead, let's be specific that we want a `Def::Fn`,
rather than blithely assuming that we can get the DefId of a qpath.

Supporting must-use closures doesn't seem like a priority, but could
conceivably be added in the future if desired (conditional on the
statement and expression attributes (#15701) story being amicable).
This commit is contained in:
Zack M. Davis 2018-03-10 14:26:33 -08:00
parent f4c1f0ce93
commit c659faba8d
1 changed files with 7 additions and 1 deletions
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8
src/librustc_lint/unused.rs
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@ -8,6 +8,7 @@
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use rustc::hir::def::Def;
use rustc::hir::def_id::DefId;
use rustc::ty;
use rustc::ty::adjustment;
@ -77,7 +78,12 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedResults {
hir::ExprCall(ref callee, _) => {
match callee.node {
hir::ExprPath(ref qpath) => {
Some(cx.tables.qpath_def(qpath, callee.hir_id))
let def = cx.tables.qpath_def(qpath, callee.hir_id);
if let Def::Fn(_) = def {
Some(def)
} else { // `Def::Local` if it was a closure, for which we
None // do not currently support must-use linting
}
},
_ => None
}