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Add note if method is called on a function object #32053

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Add note if method is called on a function object #32053

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904281f
Add note if method is called on a function object
Mar 5, 2016
87b8197
Fix code review actions in PR #32053
Mar 5, 2016
d4cc783
Add test for issue 29124
Mar 5, 2016
091d143
Use last path segment for uncalled method note if span_to_segment fails
Mar 5, 2016
086feeb
Add Help and Suggestion to issue-29124 tests
Mar 6, 2016
4f1ec4b
typeck: Fix merge conflicts
Mar 18, 2016
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112 changes: 59 additions & 53 deletions src/librustc_typeck/check/method/suggest.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -37,6 +37,42 @@ use std::cmp::Ordering;
use super::{MethodError, NoMatchData, CandidateSource, impl_item, trait_item};
use super::probe::Mode;

fn is_fn_ty<'a, 'tcx>(ty: &Ty<'tcx>, fcx: &FnCtxt<'a, 'tcx>, span: Span) -> bool {
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hooray, DRY!

let cx = fcx.tcx();
println!("{:?}", ty);
match ty.sty {
// Not all of these (e.g. unsafe fns) implement FnOnce
// so we look for these beforehand
ty::TyClosure(..) | ty::TyBareFn(..) => true,
// If it's not a simple function, look for things which implement FnOnce
_ => {
if let Ok(fn_once_trait_did) =
cx.lang_items.require(FnOnceTraitLangItem) {
let infcx = fcx.infcx();
infcx.probe(|_| {
let fn_once_substs =
Substs::new_trait(vec![infcx.next_ty_var()],
Vec::new(),
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
.to_predicate());
let mut selcx = SelectionContext::new(infcx);

return selcx.evaluate_obligation(&obligation)
})
} else {
false
}
}
}
}

pub fn report_error<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
span: Span,
rcvr_ty: Ty<'tcx>,
Expand Down Expand Up @@ -79,65 +115,35 @@ pub fn report_error<'a, 'tcx>(fcx: &FnCtxt<'a, 'tcx>,
// snippet
};

macro_rules! span_stored_function {
() => {
err.span_note(span,
&format!("use `({0}.{1})(...)` if you meant to call \
the function stored in the `{1}` field",
expr_string, item_name));
}
}

macro_rules! span_did_you_mean {
() => {
err.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 = field.ty(cx, substs);

match field_ty.sty {
// Not all of these (e.g. unsafe fns) implement FnOnce
// so we look for these beforehand
ty::TyClosure(..) | ty::TyBareFn(..) => {
span_stored_function!();
}
// If it's not a simple function, look for things which implement FnOnce
_ => {
if let Ok(fn_once_trait_did) =
cx.lang_items.require(FnOnceTraitLangItem) {
let infcx = fcx.infcx();
infcx.probe(|_| {
let fn_once_substs =
Substs::new_trait(vec![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
.to_predicate());
let mut selcx = SelectionContext::new(infcx);

if selcx.evaluate_obligation(&obligation) {
span_stored_function!();
} else {
span_did_you_mean!();
}
});
} else {
span_did_you_mean!();
}
}
if is_fn_ty(&field_ty, &fcx, span) {
err.span_note(span,
&format!("use `({0}.{1})(...)` if you meant to call \
the function stored in the `{1}` field",
expr_string, item_name));
} else {
err.span_note(span, &format!("did you mean to write `{0}.{1}`?",
expr_string, item_name));
}
}
}

if is_fn_ty(&rcvr_ty, &fcx, span) {
let expr_string = match rcvr_expr {
Some(expr) => match cx.sess.codemap().span_to_snippet(expr.span) {
Ok(expr_string) => expr_string,
_ => "s".into()
},
_ => "s".into()
};
err.fileline_note(
span,
&format!("method invoked on function type. did you \
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Perhaps the error should be something like

"stdin is a function, perhaps you wish to call it"?

And, if the span_to_snippet call works (don't use "s" as a placeholder snippet), add a span_suggestion which suggests you try {}().{} or whatever. Don't include suggestions within the notes.

mean `{}().{}(...)`?",
expr_string, item_name));
}

if !static_sources.is_empty() {
err.fileline_note(
span,
Expand Down