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Improve weight algorithm and tests
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@GuillaumeGomez
GuillaumeGomez committed May 11, 2016
1 parent b8fad79 commit 61e6169
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Showing 3 changed files with 134 additions and 60 deletions.
159 changes: 107 additions & 52 deletions src/librustc/traits/error_reporting.rs
View file
Expand Up @@ -27,10 +27,10 @@ use super::{
use fmt_macros::{Parser, Piece, Position};
use hir::def_id::DefId;
use infer::{self, InferCtxt, TypeOrigin};
use ty::{self, ToPredicate, ToPolyTraitRef, TraitRef, Ty, TyCtxt, TypeFoldable};
use ty::{self, ToPredicate, ToPolyTraitRef, TraitRef, Ty, TyCtxt, TypeFoldable, TypeVariants};
use ty::fast_reject;
use ty::fold::TypeFolder;
use ty::subst::{self, Subst};
use ty::subst::{self, ParamSpace, Subst};
use util::nodemap::{FnvHashMap, FnvHashSet};

use std::cmp;
Expand Down Expand Up @@ -63,9 +63,9 @@ impl<'a, 'gcx, 'tcx> TraitErrorKey<'tcx> {
}

fn impl_substs<'a, 'tcx>(fcx: &InferCtxt<'a, 'tcx>,
did: DefId,
obligation: PredicateObligation<'tcx>)
-> subst::Substs<'tcx> {
did: DefId,
obligation: PredicateObligation<'tcx>)
-> subst::Substs<'tcx> {
let tcx = fcx.tcx;

let ity = tcx.lookup_item_type(did);
Expand All @@ -82,44 +82,109 @@ fn impl_substs<'a, 'tcx>(fcx: &InferCtxt<'a, 'tcx>,
substs
}

/*fn check_type_parameters<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>,
trait_substs: &subst::Substs<'tcx>,
impl_substs: &subst::Substs<'tcx>,
obligation: &PredicateObligation<'tcx>) -> bool {
let trait_types = trait_substs.types.as_slice();
let impl_types = impl_substs.types.as_slice();
let mut failed = 0;
for index_to_ignore in 0..trait_types.len() {
for (index, (trait_type, impl_type)) in trait_types.iter()
.zip(impl_types.iter())
.enumerate() {
if index_to_ignore != index &&
infer::mk_eqty(infcx, true,
TypeOrigin::Misc(obligation.cause.span),
trait_type,
impl_type).is_err() {
failed += 1;
break;
}
trait AssociatedWeight {
fn get_weight(&self) -> usize;
}

impl<'a> AssociatedWeight for TypeVariants<'a> {
// First number is for "global" weight and second number is for bigger precision
fn get_weight(&self) -> usize {
match *self {
TypeVariants::TyBool => 11,
TypeVariants::TyChar => 12,
TypeVariants::TyStr => 13,
TypeVariants::TyInt(_) => 21,
TypeVariants::TyUint(_) => 22,
TypeVariants::TyFloat(_) => 23,
TypeVariants::TyRawPtr(_) => 24,
TypeVariants::TyEnum(_, _) => 31,
TypeVariants::TyStruct(_, _) => 32,
TypeVariants::TyBox(_) => 33,
TypeVariants::TyTuple(_) => 34,
TypeVariants::TyArray(_, _) => 41,
TypeVariants::TySlice(_) => 42,
TypeVariants::TyRef(_, _) => 51,
TypeVariants::TyFnDef(_, _, _) => 52,
TypeVariants::TyFnPtr(_) => 53,
TypeVariants::TyTrait(_) => 61,
TypeVariants::TyClosure(_, _) => 71,
TypeVariants::TyProjection(_) => 81,
TypeVariants::TyParam(_) => 82,
TypeVariants::TyInfer(_) => 83,
TypeVariants::TyError => 91,
}
}
failed == trait_types.len() - 1
}*/
}

// The "closer" the types are, the lesser the weight
fn get_weight_diff(a: &ty::TypeVariants, b: &TypeVariants, big_weight: bool) -> usize {
let w1 = if big_weight { a.get_weight() / 10 } else { a.get_weight() % 10 };
let w2 = if big_weight { b.get_weight() / 10 } else { b.get_weight() % 10 };

if w1 < w2 {
w2 - w1
} else {
w1 - w2
}
}

// Once we have "globally matching" types, we need to run another filter on them
fn filter_matching_types<'tcx>(weights: &[(usize, usize)],
imps: &[(DefId, subst::Substs<'tcx>)],
trait_types: &[ty::Ty<'tcx>])
-> usize {
let matching_weight = weights[0].1;
let iter = weights.iter().filter(|&&(_, weight)| weight == matching_weight);
let mut filtered_weights = vec!();

for &(pos, _) in iter {
let mut weight = 0;
for (type_to_compare, original_type) in imps[pos].1
.types
.get_slice(ParamSpace::TypeSpace)
.iter()
.zip(trait_types.iter()) {
weight += get_weight_diff(&type_to_compare.sty, &original_type.sty, false);
}
filtered_weights.push((pos, weight));
}
filtered_weights.sort_by(|a, b| a.1.cmp(&b.1));
filtered_weights[0].0
}

fn get_best_matching_type<'tcx>(imps: &[(DefId, subst::Substs<'tcx>)],
trait_types: &[ty::Ty<'tcx>]) -> usize {
let mut weights = vec!();
for (pos, imp) in imps.iter().enumerate() {
let mut weight = 0;
for (type_to_compare, original_type) in imp.1
.types
.get_slice(ParamSpace::TypeSpace)
.iter()
.zip(trait_types.iter()) {
weight += get_weight_diff(&type_to_compare.sty, &original_type.sty, true);
}
weights.push((pos, weight));
}
weights.sort_by(|a, b| a.1.cmp(&b.1));
if weights[0].1 == weights[1].1 {
filter_matching_types(&weights, &imps, trait_types)
} else {
weights[0].0
}
}

fn get_current_failing_impl<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>,
trait_ref: &TraitRef<'tcx>,
obligation: &PredicateObligation<'tcx>)
-> Option<(DefId, subst::Substs<'tcx>)> {
println!("1");
let simp = fast_reject::simplify_type(infcx.tcx,
trait_ref.self_ty(),
true);
let trait_def = infcx.tcx.lookup_trait_def(trait_ref.def_id);

match simp {
Some(_) => {
println!("2");
let mut matching_impls = Vec::new();
trait_def.for_each_impl(infcx.tcx, |def_id| {
let imp = infcx.tcx.impl_trait_ref(def_id).unwrap();
Expand All @@ -130,25 +195,19 @@ fn get_current_failing_impl<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>,
TypeOrigin::Misc(obligation.cause.span),
trait_ref.self_ty(),
imp.self_ty()).is_ok() {
//if check_type_parameters(infcx, &trait_ref.substs, &imp.substs, obligation) {
matching_impls.push((def_id, imp.substs.clone()));
//}
matching_impls.push((def_id, imp.substs.clone()));
}
println!("=> {:?} /// {:?}", def_id, imp.substs);
});
if matching_impls.len() == 0 {
println!("3");
None
} else if matching_impls.len() == 1 {
println!("4");
Some(matching_impls[0].clone())
} else {
println!("5");
let end = trait_ref.input_types().len() - 1;
// we need to determine which type is the good one!
for &(ref m, ref n) in matching_impls.iter() {
println!("=> {:?} /// {:?}", m, n);
}
Some(matching_impls[0].clone())
Some(matching_impls[get_best_matching_type(&matching_impls,
&trait_ref.input_types()[0..end])]
.clone())
}
},
None => None,
Expand All @@ -171,7 +230,6 @@ fn on_unimplemented_note<'a, 'tcx>(infcx: &InferCtxt<'a, 'tcx>,
trait_ref: ty::PolyTraitRef<'tcx>,
obligation: &PredicateObligation<'tcx>) -> Option<String> {
let trait_ref = trait_ref.skip_binder();
//let def_id = trait_ref.def_id;
let mut report = None;
let def_id = match get_current_failing_impl(infcx, trait_ref, obligation) {
Some((def_id, _)) => {
Expand Down Expand Up @@ -603,8 +661,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
// Try to report a help message

if !trait_ref.has_infer_types() &&
predicate_can_apply(infcx, trait_ref)
{
predicate_can_apply(infcx, trait_ref) {
// If a where-clause may be useful, remind the
// user that they can add it.
//
Expand Down Expand Up @@ -662,18 +719,16 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
// similar impls.

self.report_similar_impl_candidates(trait_ref, &mut err);
// If we can't show anything useful, try to find
// similar impls.
let impl_candidates =
find_similar_impl_candidates(infcx, trait_ref);
if impl_candidates.len() > 0 {
self.report_similar_impl_candidates(trait_ref, &mut err);
}
err
}
// Check if it has a custom "#[rustc_on_unimplemented]"
// error message, report with that message if it does
/*let custom_note = report_on_unimplemented(infcx, &trait_ref.0,
obligation);
if let Some(s) = custom_note {
err.fileline_note(obligation.cause.span, &s);
} else {
note_obligation_cause(infcx, &mut err, obligation);
}*/
note_obligation_cause(infcx, &mut err, obligation);
err.emit();
}

Expand Down
1 change: 1 addition & 0 deletions src/test/compile-fail/check_on_unimplemented.rs
View file
Expand Up @@ -31,4 +31,5 @@ impl Index<usize> for [i32] {
fn main() {
Index::<u32>::index(&[1, 2, 3] as &[i32], 2u32); //~ ERROR E0277
//~| NOTE a usize is required
//~| NOTE required by
}
34 changes: 26 additions & 8 deletions src/test/compile-fail/on_unimplemented.rs
View file
Expand Up @@ -19,15 +19,11 @@ trait Index<Idx: ?Sized> {
fn index(&self, index: Idx) -> &Self::Output;
}

struct Foo {
i: usize,
}

#[rustc_on_unimplemented = "a Foo is required to index into a slice"]
impl Index<Foo> for [i32] {
#[rustc_on_unimplemented = "a isize is required to index into a slice"]
impl Index<isize> for [i32] {
type Output = i32;
fn index(&self, index: Foo) -> &i32 {
&self[index.i]
fn index(&self, index: isize) -> &i32 {
&self[index as usize]
}
}

Expand All @@ -39,8 +35,30 @@ impl Index<usize> for [i32] {
}
}

trait Foo<A, B> {
fn f(&self, a: &A, b: &B);
}

#[rustc_on_unimplemented = "two i32 Foo trait takes"]
impl Foo<i32, i32> for [i32] {
fn f(&self, a: &i32, b: &i32) {}
}

#[rustc_on_unimplemented = "two u32 Foo trait takes"]
impl Foo<u32, u32> for [i32] {
fn f(&self, a: &u32, b: &u32) {}
}

#[rustc_error]
fn main() {
Index::<u32>::index(&[1, 2, 3] as &[i32], 2u32); //~ ERROR E0277
//~| NOTE a usize is required
//~| NOTE required by
Index::<i32>::index(&[1, 2, 3] as &[i32], 2i32); //~ ERROR E0277
//~| NOTE a isize is required
//~| NOTE required by

Foo::<usize, usize>::f(&[1, 2, 3] as &[i32], &2usize, &2usize); //~ ERROR E0277
//~| NOTE two u32 Foo trait
//~| NOTE required by
}

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