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Auto merge of #52648 - davidtwco:issue-52533, r=nikomatsakis
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[nll] improve the "fully elaborated type" case in region errors

Fixes #52533.

r? @nikomatsakis
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@bors
bors committed Jul 27, 2018
2 parents 6998b36 + 2e4224a commit b6cbc1e
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Showing 30 changed files with 328 additions and 149 deletions.
2 changes: 1 addition & 1 deletion src/librustc/infer/error_reporting/need_type_info.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -74,7 +74,7 @@ impl<'a, 'gcx, 'tcx> Visitor<'gcx> for FindLocalByTypeVisitor<'a, 'gcx, 'tcx> {


impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
fn extract_type_name(&self, ty: &'a Ty<'tcx>) -> String {
pub fn extract_type_name(&self, ty: &'a Ty<'tcx>) -> String {
if let ty::TyInfer(ty::TyVar(ty_vid)) = (*ty).sty {
let ty_vars = self.type_variables.borrow();
if let TypeVariableOrigin::TypeParameterDefinition(_, name) =
Expand Down
40 changes: 35 additions & 5 deletions src/librustc/util/ppaux.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -19,7 +19,7 @@ use ty::{TyError, TyStr, TyArray, TySlice, TyFloat, TyFnDef, TyFnPtr};
use ty::{TyParam, TyRawPtr, TyRef, TyNever, TyTuple};
use ty::{TyClosure, TyGenerator, TyGeneratorWitness, TyForeign, TyProjection, TyAnon};
use ty::{TyDynamic, TyInt, TyUint, TyInfer};
use ty::{self, Ty, TyCtxt, TypeFoldable, GenericParamCount, GenericParamDefKind};
use ty::{self, RegionVid, Ty, TyCtxt, TypeFoldable, GenericParamCount, GenericParamDefKind};
use util::nodemap::FxHashSet;

use std::cell::Cell;
Expand All @@ -32,6 +32,12 @@ use syntax::ast::CRATE_NODE_ID;
use syntax::symbol::{Symbol, InternedString};
use hir;

thread_local! {
/// Mechanism for highlighting of specific regions for display in NLL region inference errors.
/// Contains region to highlight and counter for number to use when highlighting.
static HIGHLIGHT_REGION: Cell<Option<(RegionVid, usize)>> = Cell::new(None)
}

macro_rules! gen_display_debug_body {
( $with:path ) => {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
Expand Down Expand Up @@ -562,6 +568,19 @@ pub fn parameterized<F: fmt::Write>(f: &mut F,
PrintContext::new().parameterized(f, substs, did, projections)
}

fn get_highlight_region() -> Option<(RegionVid, usize)> {
HIGHLIGHT_REGION.with(|hr| hr.get())
}

pub fn with_highlight_region<R>(r: RegionVid, counter: usize, op: impl FnOnce() -> R) -> R {
HIGHLIGHT_REGION.with(|hr| {
assert_eq!(hr.get(), None);
hr.set(Some((r, counter)));
let r = op();
hr.set(None);
r
})
}

impl<'a, T: Print> Print for &'a T {
fn print<F: fmt::Write>(&self, f: &mut F, cx: &mut PrintContext) -> fmt::Result {
Expand Down Expand Up @@ -733,7 +752,7 @@ define_print! {
define_print! {
() ty::RegionKind, (self, f, cx) {
display {
if cx.is_verbose {
if cx.is_verbose || get_highlight_region().is_some() {
return self.print_debug(f, cx);
}

Expand Down Expand Up @@ -905,6 +924,15 @@ impl fmt::Debug for ty::FloatVid {

impl fmt::Debug for ty::RegionVid {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
if let Some((region, counter)) = get_highlight_region() {
debug!("RegionVid.fmt: region={:?} self={:?} counter={:?}", region, self, counter);
return if *self == region {
write!(f, "'{:?}", counter)
} else {
write!(f, "'_")
}
}

write!(f, "'_#{}r", self.index())
}
}
Expand Down Expand Up @@ -1022,9 +1050,11 @@ define_print! {
TyRef(r, ty, mutbl) => {
write!(f, "&")?;
let s = r.print_to_string(cx);
write!(f, "{}", s)?;
if !s.is_empty() {
write!(f, " ")?;
if s != "'_" {
write!(f, "{}", s)?;
if !s.is_empty() {
write!(f, " ")?;
}
}
ty::TypeAndMut { ty, mutbl }.print(f, cx)
}
Expand Down
142 changes: 62 additions & 80 deletions src/librustc_mir/borrow_check/nll/region_infer/error_reporting/mod.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -31,26 +31,21 @@ mod var_name;
enum ConstraintCategory {
Cast,
Assignment,
AssignmentToUpvar,
Return,
CallArgumentToUpvar,
CallArgument,
Other,
Boring,
}

impl fmt::Display for ConstraintCategory {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
// Must end with a space. Allows for empty names to be provided.
match self {
ConstraintCategory::Assignment | ConstraintCategory::AssignmentToUpvar => {
write!(f, "assignment")
}
ConstraintCategory::Return => write!(f, "return"),
ConstraintCategory::Cast => write!(f, "cast"),
ConstraintCategory::CallArgument | ConstraintCategory::CallArgumentToUpvar => {
write!(f, "argument")
}
_ => write!(f, "free region"),
ConstraintCategory::Assignment => write!(f, "assignment "),
ConstraintCategory::Return => write!(f, "return "),
ConstraintCategory::Cast => write!(f, "cast "),
ConstraintCategory::CallArgument => write!(f, "argument "),
_ => write!(f, ""),
}
}
}
Expand Down Expand Up @@ -224,10 +219,10 @@ impl<'tcx> RegionInferenceContext<'tcx> {
"constraint_is_interesting: locations={:?} constraint={:?}",
constraint.locations, constraint
);
if let Locations::Interesting(_) = constraint.locations {
true
} else {
false

match constraint.locations {
Locations::Interesting(_) | Locations::All => true,
_ => false,
}
}

Expand Down Expand Up @@ -320,45 +315,26 @@ impl<'tcx> RegionInferenceContext<'tcx> {
}
}

let category = match (
category,
let (fr_is_local, outlived_fr_is_local): (bool, bool) = (
self.universal_regions.is_local_free_region(fr),
self.universal_regions.is_local_free_region(outlived_fr),
) {
(ConstraintCategory::Assignment, true, false) => ConstraintCategory::AssignmentToUpvar,
(ConstraintCategory::CallArgument, true, false) => {
ConstraintCategory::CallArgumentToUpvar
}
(category, _, _) => category,
);
debug!("report_error: fr_is_local={:?} outlived_fr_is_local={:?} category={:?}",
fr_is_local, outlived_fr_is_local, category);

match (category, fr_is_local, outlived_fr_is_local) {
(ConstraintCategory::Assignment, true, false) |
(ConstraintCategory::CallArgument, true, false) =>
self.report_escaping_data_error(mir, infcx, mir_def_id, fr, outlived_fr,
category, span, errors_buffer),
_ =>
self.report_general_error(mir, infcx, mir_def_id, fr, fr_is_local,
outlived_fr, outlived_fr_is_local,
category, span, errors_buffer),
};

debug!("report_error: category={:?}", category);
match category {
ConstraintCategory::AssignmentToUpvar | ConstraintCategory::CallArgumentToUpvar => self
.report_closure_error(
mir,
infcx,
mir_def_id,
fr,
outlived_fr,
category,
span,
errors_buffer,
),
_ => self.report_general_error(
mir,
infcx,
mir_def_id,
fr,
outlived_fr,
category,
span,
errors_buffer,
),
}
}

fn report_closure_error(
fn report_escaping_data_error(
&self,
mir: &Mir<'tcx>,
infcx: &InferCtxt<'_, '_, 'tcx>,
Expand All @@ -373,29 +349,23 @@ impl<'tcx> RegionInferenceContext<'tcx> {
let outlived_fr_name_and_span =
self.get_var_name_and_span_for_region(infcx.tcx, mir, outlived_fr);

let escapes_from = if infcx.tcx.is_closure(mir_def_id) { "closure" } else { "function" };

if fr_name_and_span.is_none() && outlived_fr_name_and_span.is_none() {
return self.report_general_error(
mir,
infcx,
mir_def_id,
fr,
outlived_fr,
category,
span,
errors_buffer,
);
return self.report_general_error(mir, infcx, mir_def_id,
fr, true, outlived_fr, false,
category, span, errors_buffer);
}

let mut diag = infcx
.tcx
.sess
.struct_span_err(span, &format!("borrowed data escapes outside of closure"));
let mut diag = infcx.tcx.sess.struct_span_err(
span, &format!("borrowed data escapes outside of {}", escapes_from),
);

if let Some((outlived_fr_name, outlived_fr_span)) = outlived_fr_name_and_span {
if let Some(name) = outlived_fr_name {
diag.span_label(
outlived_fr_span,
format!("`{}` is declared here, outside of the closure body", name),
format!("`{}` is declared here, outside of the {} body", name, escapes_from),
);
}
}
Expand All @@ -404,13 +374,12 @@ impl<'tcx> RegionInferenceContext<'tcx> {
if let Some(name) = fr_name {
diag.span_label(
fr_span,
format!(
"`{}` is a reference that is only valid in the closure body",
name
),
format!("`{}` is a reference that is only valid in the {} body",
name, escapes_from),
);

diag.span_label(span, format!("`{}` escapes the closure body here", name));
diag.span_label(span, format!("`{}` escapes the {} body here",
name, escapes_from));
}
}

Expand All @@ -423,7 +392,9 @@ impl<'tcx> RegionInferenceContext<'tcx> {
infcx: &InferCtxt<'_, '_, 'tcx>,
mir_def_id: DefId,
fr: RegionVid,
fr_is_local: bool,
outlived_fr: RegionVid,
outlived_fr_is_local: bool,
category: ConstraintCategory,
span: Span,
errors_buffer: &mut Vec<Diagnostic>,
Expand All @@ -434,17 +405,28 @@ impl<'tcx> RegionInferenceContext<'tcx> {
);

let counter = &mut 1;
let fr_name = self.give_region_a_name(infcx.tcx, mir, mir_def_id, fr, counter, &mut diag);
let outlived_fr_name =
self.give_region_a_name(infcx.tcx, mir, mir_def_id, outlived_fr, counter, &mut diag);

diag.span_label(
span,
format!(
"{} requires that `{}` must outlive `{}`",
category, fr_name, outlived_fr_name,
),
);
let fr_name = self.give_region_a_name(
infcx, mir, mir_def_id, fr, counter, &mut diag);
let outlived_fr_name = self.give_region_a_name(
infcx, mir, mir_def_id, outlived_fr, counter, &mut diag);

let mir_def_name = if infcx.tcx.is_closure(mir_def_id) { "closure" } else { "function" };

match (category, outlived_fr_is_local, fr_is_local) {
(ConstraintCategory::Return, true, _) => {
diag.span_label(span, format!(
"{} was supposed to return data with lifetime `{}` but it is returning \
data with lifetime `{}`",
mir_def_name, fr_name, outlived_fr_name,
));
},
_ => {
diag.span_label(span, format!(
"{}requires that `{}` must outlive `{}`",
category, fr_name, outlived_fr_name,
));
},
}

diag.buffer(errors_buffer);
}
Expand Down
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