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Auto merge of #34907 - arielb1:found-parse-error, r=nikomatsakis
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Centralize and clean type error reporting

Refactors the code that handles type errors to be cleaner and fixes various edge cases.

This made the already-bad "type mismatch resolving" error message somewhat uglier. I want to fix that in another commit before this PR is merged.

Fixes #31173

r? @jonathandturner, cc @nikomatsakis
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@bors
bors authored Jul 27, 2016
2 parents 29abe5e + 717e392 commit f2e59cc
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Showing 85 changed files with 1,017 additions and 844 deletions.
236 changes: 93 additions & 143 deletions src/librustc/infer/error_reporting.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -83,7 +83,7 @@ use hir::def_id::DefId;
use infer::{self, TypeOrigin};
use middle::region;
use ty::subst;
use ty::{self, Ty, TyCtxt, TypeFoldable};
use ty::{self, TyCtxt, TypeFoldable};
use ty::{Region, ReFree};
use ty::error::TypeError;

Expand Down Expand Up @@ -462,52 +462,6 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
}
}

fn report_type_error(&self,
trace: TypeTrace<'tcx>,
terr: &TypeError<'tcx>)
-> DiagnosticBuilder<'tcx> {
let (expected, found) = match self.values_str(&trace.values) {
Some(v) => v,
None => {
return self.tcx.sess.diagnostic().struct_dummy(); /* derived error */
}
};

let is_simple_error = if let &TypeError::Sorts(ref values) = terr {
values.expected.is_primitive() && values.found.is_primitive()
} else {
false
};

let mut err = struct_span_err!(self.tcx.sess,
trace.origin.span(),
E0308,
"{}",
trace.origin);

if !is_simple_error || check_old_school() {
err.note_expected_found(&"type", &expected, &found);
}

err.span_label(trace.origin.span(), &terr);

self.check_and_note_conflicting_crates(&mut err, terr, trace.origin.span());

match trace.origin {
TypeOrigin::MatchExpressionArm(_, arm_span, source) => match source {
hir::MatchSource::IfLetDesugar{..} => {
err.span_note(arm_span, "`if let` arm with an incompatible type");
}
_ => {
err.span_note(arm_span, "match arm with an incompatible type");
}
},
_ => ()
}

err
}

/// Adds a note if the types come from similarly named crates
fn check_and_note_conflicting_crates(&self,
err: &mut DiagnosticBuilder,
Expand Down Expand Up @@ -550,42 +504,102 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
}
}

fn note_error_origin(&self,
err: &mut DiagnosticBuilder<'tcx>,
origin: &TypeOrigin)
{
match origin {
&TypeOrigin::MatchExpressionArm(_, arm_span, source) => match source {
hir::MatchSource::IfLetDesugar {..} => {
err.span_note(arm_span, "`if let` arm with an incompatible type");
}
_ => {
err.span_note(arm_span, "match arm with an incompatible type");
}
},
_ => ()
}
}

pub fn note_type_err(&self,
diag: &mut DiagnosticBuilder<'tcx>,
origin: TypeOrigin,
values: Option<ValuePairs<'tcx>>,
terr: &TypeError<'tcx>)
{
let expected_found = match values {
None => None,
Some(values) => match self.values_str(&values) {
Some((expected, found)) => Some((expected, found)),
None => {
// Derived error. Cancel the emitter.
self.tcx.sess.diagnostic().cancel(diag);
return
}
}
};

let span = origin.span();

let mut is_simple_error = false;

if let Some((expected, found)) = expected_found {
is_simple_error = if let &TypeError::Sorts(ref values) = terr {
values.expected.is_primitive() && values.found.is_primitive()
} else {
false
};

if !is_simple_error || check_old_school() {
diag.note_expected_found(&"type", &expected, &found);
}
}

if !is_simple_error && check_old_school() {
diag.span_note(span, &format!("{}", terr));
} else {
diag.span_label(span, &terr);
}

self.note_error_origin(diag, &origin);
self.check_and_note_conflicting_crates(diag, terr, span);
self.tcx.note_and_explain_type_err(diag, terr, span);
}

pub fn report_and_explain_type_error(&self,
trace: TypeTrace<'tcx>,
terr: &TypeError<'tcx>)
-> DiagnosticBuilder<'tcx> {
let span = trace.origin.span();
let mut err = self.report_type_error(trace, terr);
self.tcx.note_and_explain_type_err(&mut err, terr, span);
err
-> DiagnosticBuilder<'tcx>
{
// FIXME: do we want to use a different error code for each origin?
let mut diag = struct_span_err!(
self.tcx.sess, trace.origin.span(), E0308,
"{}", trace.origin.as_failure_str()
);
self.note_type_err(&mut diag, trace.origin, Some(trace.values), terr);
diag
}

/// Returns a string of the form "expected `{}`, found `{}`", or None if this is a derived
/// error.
/// Returns a string of the form "expected `{}`, found `{}`".
fn values_str(&self, values: &ValuePairs<'tcx>) -> Option<(String, String)> {
match *values {
infer::Types(ref exp_found) => self.expected_found_str(exp_found),
infer::TraitRefs(ref exp_found) => self.expected_found_str(exp_found),
infer::PolyTraitRefs(ref exp_found) => self.expected_found_str(exp_found)
infer::PolyTraitRefs(ref exp_found) => self.expected_found_str(exp_found),
}
}

fn expected_found_str<T: fmt::Display + Resolvable<'tcx> + TypeFoldable<'tcx>>(
fn expected_found_str<T: fmt::Display + TypeFoldable<'tcx>>(
&self,
exp_found: &ty::error::ExpectedFound<T>)
-> Option<(String, String)>
{
let expected = exp_found.expected.resolve(self);
if expected.references_error() {
return None;
}

let found = exp_found.found.resolve(self);
if found.references_error() {
let exp_found = self.resolve_type_vars_if_possible(exp_found);
if exp_found.references_error() {
return None;
}

Some((format!("{}", expected), format!("{}", found)))
Some((format!("{}", exp_found.expected), format!("{}", exp_found.found)))
}

fn report_generic_bound_failure(&self,
Expand Down Expand Up @@ -1608,59 +1622,21 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
fn note_region_origin(&self, err: &mut DiagnosticBuilder, origin: &SubregionOrigin<'tcx>) {
match *origin {
infer::Subtype(ref trace) => {
let desc = match trace.origin {
TypeOrigin::Misc(_) => {
"types are compatible"
}
TypeOrigin::MethodCompatCheck(_) => {
"method type is compatible with trait"
}
TypeOrigin::ExprAssignable(_) => {
"expression is assignable"
}
TypeOrigin::RelateTraitRefs(_) => {
"traits are compatible"
}
TypeOrigin::RelateSelfType(_) => {
"self type matches impl self type"
}
TypeOrigin::RelateOutputImplTypes(_) => {
"trait type parameters matches those \
specified on the impl"
}
TypeOrigin::MatchExpressionArm(_, _, _) => {
"match arms have compatible types"
}
TypeOrigin::IfExpression(_) => {
"if and else have compatible types"
}
TypeOrigin::IfExpressionWithNoElse(_) => {
"if may be missing an else clause"
}
TypeOrigin::RangeExpression(_) => {
"start and end of range have compatible types"
}
TypeOrigin::EquatePredicate(_) => {
"equality where clause is satisfied"
}
};

match self.values_str(&trace.values) {
Some((expected, found)) => {
err.span_note(
trace.origin.span(),
&format!("...so that {} (expected {}, found {})",
desc, expected, found));
}
None => {
// Really should avoid printing this error at
// all, since it is derived, but that would
// require more refactoring than I feel like
// doing right now. - nmatsakis
err.span_note(
trace.origin.span(),
&format!("...so that {}", desc));
}
if let Some((expected, found)) = self.values_str(&trace.values) {
// FIXME: do we want a "the" here?
err.span_note(
trace.origin.span(),
&format!("...so that {} (expected {}, found {})",
trace.origin.as_requirement_str(), expected, found));
} else {
// FIXME: this really should be handled at some earlier stage. Our
// handling of region checking when type errors are present is
// *terrible*.

err.span_note(
trace.origin.span(),
&format!("...so that {}",
trace.origin.as_requirement_str()));
}
}
infer::Reborrow(span) => {
Expand Down Expand Up @@ -1803,32 +1779,6 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
}
}

pub trait Resolvable<'tcx> {
fn resolve<'a, 'gcx>(&self, infcx: &InferCtxt<'a, 'gcx, 'tcx>) -> Self;
}

impl<'tcx> Resolvable<'tcx> for Ty<'tcx> {
fn resolve<'a, 'gcx>(&self, infcx: &InferCtxt<'a, 'gcx, 'tcx>) -> Ty<'tcx> {
infcx.resolve_type_vars_if_possible(self)
}
}

impl<'tcx> Resolvable<'tcx> for ty::TraitRef<'tcx> {
fn resolve<'a, 'gcx>(&self, infcx: &InferCtxt<'a, 'gcx, 'tcx>)
-> ty::TraitRef<'tcx> {
infcx.resolve_type_vars_if_possible(self)
}
}

impl<'tcx> Resolvable<'tcx> for ty::PolyTraitRef<'tcx> {
fn resolve<'a, 'gcx>(&self,
infcx: &InferCtxt<'a, 'gcx, 'tcx>)
-> ty::PolyTraitRef<'tcx>
{
infcx.resolve_type_vars_if_possible(self)
}
}

fn lifetimes_in_scope<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
scope_id: ast::NodeId)
-> Vec<hir::LifetimeDef> {
Expand Down
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