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auto merge of #18264 : jakub-/rust/var-ids-in-error-messages, r=nikomatsakis

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This PR aims to improve the readability of diagnostic messages that involve unresolved type variables. Currently, messages like the following:

```rust
mismatched types: expected `core::result::Result<uint,()>`, found `core::option::Option<<generic #1>>`
<anon>:6     let a: Result<uint, ()> = None;
                                       ^~~~
mismatched types: expected `&mut <generic #2>`, found `uint`
<anon>:7     f(42u);
               ^~~
```

tend to appear unapproachable to new users. [0] While specific type var IDs are valuable in
diagnostics that deal with more than one such variable, in practice many messages
only mention one. In those cases, leaving out the specific number makes the messages
slightly less terrifying.

```rust
mismatched types: expected `core::result::Result<uint, ()>`, found `core::option::Option<_>`
<anon>:6     let a: Result<uint, ()> = None;
                                       ^~~~
mismatched types: expected `&mut _`, found `uint`
<anon>:7     f(42u);
               ^~~
```

As you can see, I also tweaked the aesthetics slightly by changing type variables to use the type hole syntax _. For integer variables, the syntax used is:

```rust
mismatched types: expected `core::result::Result<uint, ()>`, found `core::option::Option<_#1i>`
<anon>:6     let a: Result<uint, ()> = Some(1);
```

and float variables:

```rust
mismatched types: expected `core::result::Result<uint, ()>`, found `core::option::Option<_#1f>`
<anon>:6     let a: Result<uint, ()> = Some(0.5);
```

[0] https://twitter.com/coda/status/517713085465772032

Closes https://github.com/rust-lang/rust/issues/2632.
Closes https://github.com/rust-lang/rust/issues/3404.
Closes https://github.com/rust-lang/rust/issues/18426.
This commit is contained in:
bors 2014-10-31 11:16:44 +00:00
commit 82045ca360
29 changed files with 241 additions and 195 deletions
Download patch file Download diff file Expand all files Collapse all files

41
src/librustc/middle/ty.rs
View file

@ -1032,10 +1032,8 @@ pub enum type_err {
terr_ref_mutability,
terr_vec_mutability,
terr_tuple_size(expected_found<uint>),
terr_fixed_array_size(expected_found<uint>),
terr_ty_param_size(expected_found<uint>),
terr_record_size(expected_found<uint>),
terr_record_mutability,
terr_record_fields(expected_found<Ident>),
terr_arg_count,
terr_regions_does_not_outlive(Region, Region),
terr_regions_not_same(Region, Region),
@ -3790,8 +3788,8 @@ pub fn ty_sort_string(cx: &ctxt, t: t) -> String {
ty_enum(id, _) => format!("enum {}", item_path_str(cx, id)),
ty_uniq(_) => "box".to_string(),
ty_vec(_, Some(_)) => "array".to_string(),
ty_vec(_, None) => "unsized array".to_string(),
ty_vec(_, Some(n)) => format!("array of {} elements", n),
ty_vec(_, None) => "slice".to_string(),
ty_ptr(_) => "*-ptr".to_string(),
ty_rptr(_, _) => "&-ptr".to_string(),
ty_bare_fn(_) => "extern fn".to_string(),
@ -3874,27 +3872,18 @@ pub fn type_err_to_str(cx: &ctxt, err: &type_err) -> String {
values.expected,
values.found)
}
terr_fixed_array_size(values) => {
format!("expected an array with a fixed size of {} elements, \
found one with {} elements",
values.expected,
values.found)
}
terr_tuple_size(values) => {
format!("expected a tuple with {} elements, \
found one with {} elements",
values.expected,
values.found)
}
terr_record_size(values) => {
format!("expected a record with {} fields, \
found one with {} fields",
values.expected,
values.found)
}
terr_record_mutability => {
"record elements differ in mutability".to_string()
}
terr_record_fields(values) => {
format!("expected a record with field `{}`, found one \
with field `{}`",
token::get_ident(values.expected),
token::get_ident(values.found))
}
terr_arg_count => {
"incorrect number of function parameters".to_string()
}
@ -3923,9 +3912,15 @@ pub fn type_err_to_str(cx: &ctxt, err: &type_err) -> String {
trait_store_to_string(cx, (*values).found))
}
terr_sorts(values) => {
format!("expected {}, found {}",
ty_sort_string(cx, values.expected),
ty_sort_string(cx, values.found))
// A naive approach to making sure that we're not reporting silly errors such as:
// (expected closure, found closure).
let expected_str = ty_sort_string(cx, values.expected);
let found_str = ty_sort_string(cx, values.found);
if expected_str == found_str {
format!("expected {}, found a different {}", expected_str, found_str)
} else {
format!("expected {}, found {}", expected_str, found_str)
}
}
terr_traits(values) => {
format!("expected trait `{}`, found trait `{}`",

10
src/librustc/middle/typeck/infer/combine.rs
View file

@ -515,6 +515,16 @@ pub fn super_tys<'tcx, C: Combine<'tcx>>(this: &C, a: ty::t, b: ty::t) -> cres<t
Ok(ty::mk_rptr(tcx, r, mt))
}
(&ty::ty_vec(a_t, Some(sz_a)), &ty::ty_vec(b_t, Some(sz_b))) => {
this.tys(a_t, b_t).and_then(|t| {
if sz_a == sz_b {
Ok(ty::mk_vec(tcx, t, Some(sz_a)))
} else {
Err(ty::terr_fixed_array_size(expected_found(this, sz_a, sz_b)))
}
})
}
(&ty::ty_vec(a_t, sz_a), &ty::ty_vec(b_t, sz_b)) => {
this.tys(a_t, b_t).and_then(|t| {
if sz_a == sz_b {

12
src/librustc/middle/typeck/infer/error_reporting.rs
View file

@ -111,7 +111,7 @@ pub trait ErrorReporting {
fn values_str(&self, values: &ValuePairs) -> Option<String>;
fn expected_found_str<T:UserString+Resolvable>(
fn expected_found_str<T: UserString + Resolvable>(
&self,
exp_found: &ty::expected_found<T>)
-> Option<String>;
@ -396,16 +396,12 @@ impl<'a, 'tcx> ErrorReporting for InferCtxt<'a, 'tcx> {
* or None if this is a derived error.
*/
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::Types(ref exp_found) => self.expected_found_str(exp_found),
infer::TraitRefs(ref exp_found) => self.expected_found_str(exp_found)
}
}
fn expected_found_str<T:UserString+Resolvable>(
fn expected_found_str<T: UserString + Resolvable>(
&self,
exp_found: &ty::expected_found<T>)
-> Option<String>

65
src/librustc/middle/typeck/infer/mod.rs
View file

@ -36,7 +36,8 @@ use syntax::ast;
use syntax::codemap;
use syntax::codemap::Span;
use util::common::indent;
use util::ppaux::{bound_region_to_string, ty_to_string, trait_ref_to_string, Repr};
use util::ppaux::{bound_region_to_string, ty_to_string};
use util::ppaux::{trait_ref_to_string, Repr};
use self::coercion::Coerce;
use self::combine::{Combine, CombineFields};
@ -900,31 +901,24 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
err: Option<&ty::type_err>) {
debug!("hi! expected_ty = {}, actual_ty = {}", expected_ty, actual_ty);
let error_str = err.map_or("".to_string(), |t_err| {
format!(" ({})", ty::type_err_to_str(self.tcx, t_err))
});
let resolved_expected = expected_ty.map(|e_ty| {
self.resolve_type_vars_if_possible(e_ty)
});
if !resolved_expected.map_or(false, |e| { ty::type_is_error(e) }) {
match resolved_expected {
None => {
self.tcx
.sess
.span_err(sp,
format!("{}{}",
mk_msg(None, actual_ty),
error_str).as_slice())
match resolved_expected {
Some(t) if ty::type_is_error(t) => (),
_ => {
let error_str = err.map_or("".to_string(), |t_err| {
format!(" ({})", ty::type_err_to_str(self.tcx, t_err))
});
self.tcx.sess.span_err(sp, format!("{}{}",
mk_msg(resolved_expected.map(|t| self.ty_to_string(t)), actual_ty),
error_str).as_slice());
for err in err.iter() {
ty::note_and_explain_type_err(self.tcx, *err)
}
Some(e) => {
self.tcx.sess.span_err(sp,
format!("{}{}",
mk_msg(Some(self.ty_to_string(e)), actual_ty),
error_str).as_slice());
}
}
for err in err.iter() {
ty::note_and_explain_type_err(self.tcx, *err)
}
}
}
@ -945,25 +939,18 @@ impl<'a, 'tcx> InferCtxt<'a, 'tcx> {
}
pub fn report_mismatched_types(&self,
sp: Span,
e: ty::t,
a: ty::t,
span: Span,
expected: ty::t,
actual: ty::t,
err: &ty::type_err) {
let resolved_expected =
self.resolve_type_vars_if_possible(e);
let mk_msg = match ty::get(resolved_expected).sty {
// Don't report an error if expected is ty_err
ty::ty_err => return,
_ => {
// if I leave out : String, it infers &str and complains
|actual: String| {
format!("mismatched types: expected `{}`, found `{}`",
self.ty_to_string(resolved_expected),
actual)
}
}
let trace = TypeTrace {
origin: Misc(span),
values: Types(ty::expected_found {
expected: expected,
found: actual
})
};
self.type_error_message(sp, mk_msg, a, Some(err));
self.report_and_explain_type_error(trace, err);
}
pub fn replace_late_bound_regions_with_fresh_regions(&self,

184
src/librustc/util/ppaux.rs
View file

@ -229,7 +229,9 @@ pub fn mutability_to_string(m: ast::Mutability) -> String {
}
pub fn mt_to_string(cx: &ctxt, m: &mt) -> String {
format!("{}{}", mutability_to_string(m.mutbl), ty_to_string(cx, m.ty))
format!("{}{}",
mutability_to_string(m.mutbl),
ty_to_string(cx, m.ty))
}
pub fn trait_store_to_string(cx: &ctxt, s: ty::TraitStore) -> String {
@ -256,9 +258,6 @@ pub fn trait_ref_to_string(cx: &ctxt, trait_ref: &ty::TraitRef) -> String {
}
pub fn ty_to_string(cx: &ctxt, typ: t) -> String {
fn fn_input_to_string(cx: &ctxt, input: ty::t) -> String {
ty_to_string(cx, input).to_string()
}
fn bare_fn_to_string(cx: &ctxt,
fn_style: ast::FnStyle,
abi: abi::Abi,
@ -340,7 +339,10 @@ pub fn ty_to_string(cx: &ctxt, typ: t) -> String {
sig: &ty::FnSig,
bounds: &str) {
s.push(bra);
let strs: Vec<String> = sig.inputs.iter().map(|a| fn_input_to_string(cx, *a)).collect();
let strs = sig.inputs
.iter()
.map(|a| ty_to_string(cx, *a))
.collect::<Vec<_>>();
s.push_str(strs.connect(", ").as_slice());
if sig.variadic {
s.push_str(", ...");
@ -355,7 +357,7 @@ pub fn ty_to_string(cx: &ctxt, typ: t) -> String {
match sig.output {
ty::FnConverging(t) => {
if !ty::type_is_nil(t) {
s.push_str(" -> ");
s.push_str(" -> ");
s.push_str(ty_to_string(cx, t).as_slice());
}
}
@ -365,82 +367,96 @@ pub fn ty_to_string(cx: &ctxt, typ: t) -> String {
}
}
// if there is an id, print that instead of the structural type:
/*for def_id in ty::type_def_id(typ).iter() {
// note that this typedef cannot have type parameters
return ty::item_path_str(cx, *def_id);
}*/
fn infer_ty_to_string(cx: &ctxt, ty: ty::InferTy) -> String {
let print_var_ids = cx.sess.verbose();
match ty {
ty::TyVar(ty::TyVid { index: vid }) if print_var_ids =>
format!("_#{}", vid),
ty::IntVar(ty::IntVid { index: vid }) if print_var_ids =>
format!("_#{}i", vid),
ty::FloatVar(ty::FloatVid { index: vid }) if print_var_ids =>
format!("_#{}f", vid),
ty::TyVar(_) | ty::IntVar(_) | ty::FloatVar(_) =>
"_".to_string(),
ty::SkolemizedTy(v) => format!("SkolemizedTy({})", v),
ty::SkolemizedIntTy(v) => format!("SkolemizedIntTy({})", v)
}
}
// pretty print the structural type representation:
return match ty::get(typ).sty {
ty_nil => "()".to_string(),
ty_bool => "bool".to_string(),
ty_char => "char".to_string(),
ty_int(t) => ast_util::int_ty_to_string(t, None).to_string(),
ty_uint(t) => ast_util::uint_ty_to_string(t, None).to_string(),
ty_float(t) => ast_util::float_ty_to_string(t).to_string(),
ty_uniq(typ) => format!("Box<{}>", ty_to_string(cx, typ)),
ty_ptr(ref tm) => {
format!("*{} {}", match tm.mutbl {
ast::MutMutable => "mut",
ast::MutImmutable => "const",
}, ty_to_string(cx, tm.ty))
}
ty_rptr(r, ref tm) => {
let mut buf = region_ptr_to_string(cx, r);
buf.push_str(mt_to_string(cx, tm).as_slice());
buf
}
ty_open(typ) => format!("opened<{}>", ty_to_string(cx, typ)),
ty_tup(ref elems) => {
let strs: Vec<String> = elems.iter().map(|elem| ty_to_string(cx, *elem)).collect();
format!("({})", strs.connect(","))
}
ty_closure(ref f) => {
closure_to_string(cx, &**f)
}
ty_bare_fn(ref f) => {
bare_fn_to_string(cx, f.fn_style, f.abi, None, &f.sig)
}
ty_infer(infer_ty) => infer_ty.to_string(),
ty_err => "[type error]".to_string(),
ty_param(ref param_ty) => {
param_ty.repr(cx)
}
ty_enum(did, ref substs) | ty_struct(did, ref substs) => {
let base = ty::item_path_str(cx, did);
let generics = ty::lookup_item_type(cx, did).generics;
parameterized(cx, base.as_slice(), substs, &generics)
}
ty_trait(box ty::TyTrait {
def_id: did, ref substs, ref bounds
}) => {
let base = ty::item_path_str(cx, did);
let trait_def = ty::lookup_trait_def(cx, did);
let ty = parameterized(cx, base.as_slice(),
substs, &trait_def.generics);
let bound_str = bounds.user_string(cx);
let bound_sep = if bound_str.is_empty() { "" } else { "+" };
format!("{}{}{}",
ty,
bound_sep,
bound_str)
}
ty_str => "str".to_string(),
ty_unboxed_closure(ref did, _, ref substs) => {
let unboxed_closures = cx.unboxed_closures.borrow();
unboxed_closures.find(did).map(|cl| {
closure_to_string(cx, &cl.closure_type.subst(cx, substs))
}).unwrap_or_else(|| "closure".to_string())
}
ty_vec(t, sz) => {
match sz {
Some(n) => {
format!("[{}, ..{}]", ty_to_string(cx, t), n)
}
None => format!("[{}]", ty_to_string(cx, t)),
}
}
match ty::get(typ).sty {
ty_nil => "()".to_string(),
ty_bool => "bool".to_string(),
ty_char => "char".to_string(),
ty_int(t) => ast_util::int_ty_to_string(t, None).to_string(),
ty_uint(t) => ast_util::uint_ty_to_string(t, None).to_string(),
ty_float(t) => ast_util::float_ty_to_string(t).to_string(),
ty_uniq(typ) => format!("Box<{}>", ty_to_string(cx, typ)),
ty_ptr(ref tm) => {
format!("*{} {}", match tm.mutbl {
ast::MutMutable => "mut",
ast::MutImmutable => "const",
}, ty_to_string(cx, tm.ty))
}
ty_rptr(r, ref tm) => {
let mut buf = region_ptr_to_string(cx, r);
buf.push_str(mt_to_string(cx, tm).as_slice());
buf
}
ty_open(typ) =>
format!("opened<{}>", ty_to_string(cx, typ)),
ty_tup(ref elems) => {
let strs = elems
.iter()
.map(|elem| ty_to_string(cx, *elem))
.collect::<Vec<_>>();
match strs.as_slice() {
[ref string] => format!("({},)", string),
strs => format!("({})", strs.connect(", "))
}
}
ty_closure(ref f) => {
closure_to_string(cx, &**f)
}
ty_bare_fn(ref f) => {
bare_fn_to_string(cx, f.fn_style, f.abi, None, &f.sig)
}
ty_infer(infer_ty) => infer_ty_to_string(cx, infer_ty),
ty_err => "[type error]".to_string(),
ty_param(ref param_ty) => param_ty.repr(cx),
ty_enum(did, ref substs) | ty_struct(did, ref substs) => {
let base = ty::item_path_str(cx, did);
let generics = ty::lookup_item_type(cx, did).generics;
parameterized(cx, base.as_slice(), substs, &generics)
}
ty_trait(box ty::TyTrait {
def_id: did, ref substs, ref bounds
}) => {
let base = ty::item_path_str(cx, did);
let trait_def = ty::lookup_trait_def(cx, did);
let ty = parameterized(cx, base.as_slice(),
substs, &trait_def.generics);
let bound_str = bounds.user_string(cx);
let bound_sep = if bound_str.is_empty() { "" } else { "+" };
format!("{}{}{}",
ty,
bound_sep,
bound_str)
}
ty_str => "str".to_string(),
ty_unboxed_closure(ref did, _, ref substs) => {
let unboxed_closures = cx.unboxed_closures.borrow();
unboxed_closures.find(did).map(|cl| {
closure_to_string(cx, &cl.closure_type.subst(cx, substs))
}).unwrap_or_else(|| "closure".to_string())
}
ty_vec(t, sz) => {
let inner_str = ty_to_string(cx, t);
match sz {
Some(n) => format!("[{}, ..{}]", inner_str, n),
None => format!("[{}]", inner_str),
}
}
}
}
@ -470,15 +486,15 @@ pub fn parameterized(cx: &ctxt,
subst::NonerasedRegions(ref regions) => {
for &r in regions.iter() {
let s = region_to_string(cx, "", false, r);
if !s.is_empty() {
strs.push(s)
} else {
if s.is_empty() {
// This happens when the value of the region
// parameter is not easily serialized. This may be
// because the user omitted it in the first place,
// or because it refers to some block in the code,
// etc. I'm not sure how best to serialize this.
strs.push(format!("'_"));
} else {
strs.push(s)
}
}
}
@ -515,7 +531,7 @@ pub fn parameterized(cx: &ctxt,
}
if strs.len() > 0u {
format!("{}<{}>", base, strs.connect(","))
format!("{}<{}>", base, strs.connect(", "))
} else {
format!("{}", base)
}