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Handle error case safely with a fallback

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This commit is contained in:
Paul Faria 2015-06-15 12:28:14 -04:00
parent 0230a530ce
commit c8a0b0eece
1 changed files with 32 additions and 23 deletions
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55
src/librustc_typeck/check/method/suggest.rs
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@ -73,33 +73,42 @@ pub fn report_error<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
// snippet
};
// Determine if the field can be used as a function in some way
let fn_once_trait_did = match cx.lang_items.require(FnOnceTraitLangItem) {
Ok(trait_did) => trait_did,
Err(err) => cx.sess.fatal(&err[..])
};
fn span_stored_function() {
cx.sess.span_note(span, &format!("use `({0}.{1})(...)` if you meant to call \
the function stored in the `{1}` field",
expr_string, item_name));
}
let field_ty = ty::lookup_field_type(cx, did, field.id, substs);
let field_ty_substs = Substs::new_trait(vec![fcx.inh.infcx.next_ty_var()],
Vec::new(),
field_ty);
let trait_ref = ty::TraitRef::new(fn_once_trait_did,
cx.mk_substs(field_ty_substs));
let poly_trait_ref = trait_ref.to_poly_trait_ref();
let obligation = Obligation::misc(span,
fcx.body_id,
poly_trait_ref.as_predicate());
let mut selcx = SelectionContext::new(fcx.infcx(), fcx);
if selcx.evaluate_obligation(&obligation) {
cx.sess.span_note(span,
&format!("use `({0}.{1})(...)` if you meant to call the \
function stored in the `{1}` field",
expr_string, item_name));
} else {
fn span_did_you_mean() {
cx.sess.span_note(span, &format!("did you mean to write `{0}.{1}`?",
expr_string, item_name));
}
// Determine if the field can be used as a function in some way
let field_ty = ty::lookup_field_type(cx, did, field.id, substs);
if let Ok(fn_once_trait_did) = cx.lang_items.require(FnOnceTraitLangItem) {
let fn_once_substs = Substs::new_trait(vec![fcx.inh.infcx.next_ty_var()],
Vec::new(),
field_ty);
let trait_ref = ty::TraitRef::new(fn_once_trait_did,
cx.mk_substs(fn_once_substs));
let poly_trait_ref = trait_ref.to_poly_trait_ref();
let obligation = Obligation::misc(span,
fcx.body_id,
poly_trait_ref.as_predicate());
let mut selcx = SelectionContext::new(fcx.infcx(), fcx);
if selcx.evaluate_obligation(&obligation) {
span_stored_function();
} else {
span_did_you_mean();
}
} else {
match field_ty.sty {
ty::TyClosure(_,_) | ty::TyFnPtr(_,_) => span_stored_function(),
_ => span_did_you_mean(),
}
}
}
}