user0/rust
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

Auto merge of #67597 - estebank:placeholder-type, r=oli-obk

Browse source 
Suggest type param when encountering `_` in item signatures

Fix #27435.
This commit is contained in:
bors 2019-12-31 09:50:49 +00:00
commit 71bb0ff33e
9 changed files with 519 additions and 122 deletions
Download patch file Download diff file Expand all files Collapse all files

34
src/librustc_typeck/astconv.rs
View file

@ -2,8 +2,10 @@
//! The main routine here is `ast_ty_to_ty()`; each use is parameterized by an
//! instance of `AstConv`.
use crate::collect::PlaceholderHirTyCollector;
use crate::hir::def::{CtorOf, DefKind, Res};
use crate::hir::def_id::DefId;
use crate::hir::intravisit::Visitor;
use crate::hir::print;
use crate::hir::{self, ExprKind, GenericArg, GenericArgs};
use crate::lint;
@ -65,6 +67,9 @@ pub trait AstConv<'tcx> {
/// Returns the type to use when a type is omitted.
fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx>;
/// Returns `true` if `_` is allowed in type signatures in the current context.
fn allow_ty_infer(&self) -> bool;
/// Returns the const to use when a const is omitted.
fn ct_infer(
&self,
@ -2591,7 +2596,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
}
hir::TyKind::BareFn(ref bf) => {
require_c_abi_if_c_variadic(tcx, &bf.decl, bf.abi, ast_ty.span);
tcx.mk_fn_ptr(self.ty_of_fn(bf.unsafety, bf.abi, &bf.decl))
tcx.mk_fn_ptr(self.ty_of_fn(bf.unsafety, bf.abi, &bf.decl, &[], None))
}
hir::TyKind::TraitObject(ref bounds, ref lifetime) => {
self.conv_object_ty_poly_trait_ref(ast_ty.span, bounds, lifetime)
@ -2756,14 +2761,24 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
unsafety: hir::Unsafety,
abi: abi::Abi,
decl: &hir::FnDecl<'_>,
generic_params: &[hir::GenericParam<'_>],
ident_span: Option<Span>,
) -> ty::PolyFnSig<'tcx> {
debug!("ty_of_fn");
let tcx = self.tcx();
let input_tys = decl.inputs.iter().map(|a| self.ty_of_arg(a, None));
// We proactively collect all the infered type params to emit a single error per fn def.
let mut visitor = PlaceholderHirTyCollector::default();
for ty in decl.inputs {
visitor.visit_ty(ty);
}
let input_tys = decl.inputs.iter().map(|a| self.ty_of_arg(a, None));
let output_ty = match decl.output {
hir::Return(ref output) => self.ast_ty_to_ty(output),
hir::Return(ref output) => {
visitor.visit_ty(output);
self.ast_ty_to_ty(output)
}
hir::DefaultReturn(..) => tcx.mk_unit(),
};
@ -2772,6 +2787,19 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
let bare_fn_ty =
ty::Binder::bind(tcx.mk_fn_sig(input_tys, output_ty, decl.c_variadic, unsafety, abi));
if !self.allow_ty_infer() {
// We always collect the spans for placeholder types when evaluating `fn`s, but we
// only want to emit an error complaining about them if infer types (`_`) are not
// allowed. `allow_ty_infer` gates this behavior.
crate::collect::placeholder_type_error(
tcx,
ident_span.unwrap_or(DUMMY_SP),
generic_params,
visitor.0,
ident_span.is_some(),
);
}
// Find any late-bound regions declared in return type that do
// not appear in the arguments. These are not well-formed.
//

36
src/librustc_typeck/check/mod.rs
View file

@ -756,6 +756,7 @@ pub fn provide(providers: &mut Providers<'_>) {
*providers = Providers {
typeck_item_bodies,
typeck_tables_of,
diagnostic_only_typeck_tables_of,
has_typeck_tables,
adt_destructor,
used_trait_imports,
@ -941,7 +942,31 @@ where
val.fold_with(&mut FixupFolder { tcx })
}
fn typeck_tables_of(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::TypeckTables<'_> {
fn typeck_tables_of<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> &ty::TypeckTables<'tcx> {
let fallback = move || tcx.type_of(def_id);
typeck_tables_of_with_fallback(tcx, def_id, fallback)
}
/// Used only to get `TypeckTables` for type inference during error recovery.
/// Currently only used for type inference of `static`s and `const`s to avoid type cycle errors.
fn diagnostic_only_typeck_tables_of<'tcx>(
tcx: TyCtxt<'tcx>,
def_id: DefId,
) -> &ty::TypeckTables<'tcx> {
assert!(def_id.is_local());
let fallback = move || {
let span = tcx.hir().span(tcx.hir().as_local_hir_id(def_id).unwrap());
tcx.sess.delay_span_bug(span, "diagnostic only typeck table used");
tcx.types.err
};
typeck_tables_of_with_fallback(tcx, def_id, fallback)
}
fn typeck_tables_of_with_fallback<'tcx>(
tcx: TyCtxt<'tcx>,
def_id: DefId,
fallback: impl Fn() -> Ty<'tcx> + 'tcx,
) -> &'tcx ty::TypeckTables<'tcx> {
// Closures' tables come from their outermost function,
// as they are part of the same "inference environment".
let outer_def_id = tcx.closure_base_def_id(def_id);
@ -963,7 +988,7 @@ fn typeck_tables_of(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::TypeckTables<'_> {
let fcx = if let (Some(header), Some(decl)) = (fn_header, fn_decl) {
let fn_sig = if crate::collect::get_infer_ret_ty(&decl.output).is_some() {
let fcx = FnCtxt::new(&inh, param_env, body.value.hir_id);
AstConv::ty_of_fn(&fcx, header.unsafety, header.abi, decl)
AstConv::ty_of_fn(&fcx, header.unsafety, header.abi, decl, &[], None)
} else {
tcx.fn_sig(def_id)
};
@ -990,7 +1015,7 @@ fn typeck_tables_of(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::TypeckTables<'_> {
hir::TyKind::Infer => Some(AstConv::ast_ty_to_ty(&fcx, ty)),
_ => None,
})
.unwrap_or_else(|| tcx.type_of(def_id));
.unwrap_or_else(fallback);
let expected_type = fcx.normalize_associated_types_in(body.value.span, &expected_type);
fcx.require_type_is_sized(expected_type, body.value.span, traits::ConstSized);
@ -1069,6 +1094,7 @@ fn typeck_tables_of(tcx: TyCtxt<'_>, def_id: DefId) -> &ty::TypeckTables<'_> {
let ty = fcx.normalize_ty(span, ty);
fcx.require_type_is_sized(ty, span, code);
}
fcx.select_all_obligations_or_error();
if fn_decl.is_some() {
@ -2563,6 +2589,10 @@ impl<'a, 'tcx> AstConv<'tcx> for FnCtxt<'a, 'tcx> {
Some(self.next_region_var(v))
}
fn allow_ty_infer(&self) -> bool {
true
}
fn ty_infer(&self, param: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
if let Some(param) = param {
if let GenericArgKind::Type(ty) = self.var_for_def(span, param).unpack() {

163
src/librustc_typeck/collect.rs
View file

@ -102,10 +102,90 @@ pub struct ItemCtxt<'tcx> {
///////////////////////////////////////////////////////////////////////////
#[derive(Default)]
crate struct PlaceholderHirTyCollector(crate Vec<Span>);
impl<'v> Visitor<'v> for PlaceholderHirTyCollector {
fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'v> {
NestedVisitorMap::None
}
fn visit_ty(&mut self, t: &'v hir::Ty<'v>) {
if let hir::TyKind::Infer = t.kind {
self.0.push(t.span);
}
hir::intravisit::walk_ty(self, t)
}
}
struct CollectItemTypesVisitor<'tcx> {
tcx: TyCtxt<'tcx>,
}
/// If there are any placeholder types (`_`), emit an error explaining that this is not allowed
/// and suggest adding type parameters in the appropriate place, taking into consideration any and
/// all already existing generic type parameters to avoid suggesting a name that is already in use.
crate fn placeholder_type_error(
tcx: TyCtxt<'tcx>,
ident_span: Span,
generics: &[hir::GenericParam<'_>],
placeholder_types: Vec<Span>,
suggest: bool,
) {
if placeholder_types.is_empty() {
return;
}
// This is the whitelist of possible parameter names that we might suggest.
let possible_names = ["T", "K", "L", "A", "B", "C"];
let used_names = generics
.iter()
.filter_map(|p| match p.name {
hir::ParamName::Plain(ident) => Some(ident.name),
_ => None,
})
.collect::<Vec<_>>();
let type_name = possible_names
.iter()
.find(|n| !used_names.contains(&Symbol::intern(n)))
.unwrap_or(&"ParamName");
let mut sugg: Vec<_> =
placeholder_types.iter().map(|sp| (*sp, type_name.to_string())).collect();
if generics.is_empty() {
sugg.push((ident_span.shrink_to_hi(), format!("<{}>", type_name)));
} else {
sugg.push((
generics.iter().last().unwrap().span.shrink_to_hi(),
format!(", {}", type_name),
));
}
let mut err = bad_placeholder_type(tcx, placeholder_types);
if suggest {
err.multipart_suggestion(
"use type parameters instead",
sugg,
Applicability::HasPlaceholders,
);
}
err.emit();
}
fn reject_placeholder_type_signatures_in_item(tcx: TyCtxt<'tcx>, item: &'tcx hir::Item<'tcx>) {
let (generics, suggest) = match &item.kind {
hir::ItemKind::Union(_, generics)
| hir::ItemKind::Enum(_, generics)
| hir::ItemKind::Struct(_, generics) => (&generics.params[..], true),
hir::ItemKind::TyAlias(_, generics) => (&generics.params[..], false),
// `static`, `fn` and `const` are handled elsewhere to suggest appropriate type.
_ => return,
};
let mut visitor = PlaceholderHirTyCollector::default();
visitor.visit_item(item);
placeholder_type_error(tcx, item.ident.span, generics, visitor.0, suggest);
}
impl Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
NestedVisitorMap::OnlyBodies(&self.tcx.hir())
@ -113,6 +193,7 @@ impl Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
fn visit_item(&mut self, item: &'tcx hir::Item<'tcx>) {
convert_item(self.tcx, item.hir_id);
reject_placeholder_type_signatures_in_item(self.tcx, item);
intravisit::walk_item(self, item);
}
@ -157,15 +238,21 @@ impl Visitor<'tcx> for CollectItemTypesVisitor<'tcx> {
///////////////////////////////////////////////////////////////////////////
// Utility types and common code for the above passes.
fn bad_placeholder_type(tcx: TyCtxt<'tcx>, span: Span) -> errors::DiagnosticBuilder<'tcx> {
let mut diag = struct_span_err!(
fn bad_placeholder_type(
tcx: TyCtxt<'tcx>,
mut spans: Vec<Span>,
) -> errors::DiagnosticBuilder<'tcx> {
spans.sort();
let mut err = struct_span_err!(
tcx.sess,
span,
spans.clone(),
E0121,
"the type placeholder `_` is not allowed within types on item signatures",
);
diag.span_label(span, "not allowed in type signatures");
diag
for span in spans {
err.span_label(span, "not allowed in type signatures");
}
err
}
impl ItemCtxt<'tcx> {
@ -195,9 +282,12 @@ impl AstConv<'tcx> for ItemCtxt<'tcx> {
None
}
fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
bad_placeholder_type(self.tcx(), span).emit();
fn allow_ty_infer(&self) -> bool {
false
}
fn ty_infer(&self, _: Option<&ty::GenericParamDef>, span: Span) -> Ty<'tcx> {
self.tcx().sess.delay_span_bug(span, "bad placeholder type");
self.tcx().types.err
}
@ -207,7 +297,7 @@ impl AstConv<'tcx> for ItemCtxt<'tcx> {
_: Option<&ty::GenericParamDef>,
span: Span,
) -> &'tcx Const<'tcx> {
bad_placeholder_type(self.tcx(), span).emit();
bad_placeholder_type(self.tcx(), vec![span]).emit();
self.tcx().consts.err
}
@ -1132,7 +1222,7 @@ fn infer_placeholder_type(
span: Span,
item_ident: Ident,
) -> Ty<'_> {
let ty = tcx.typeck_tables_of(def_id).node_type(body_id.hir_id);
let ty = tcx.diagnostic_only_typeck_tables_of(def_id).node_type(body_id.hir_id);
// If this came from a free `const` or `static mut?` item,
// then the user may have written e.g. `const A = 42;`.
@ -1152,7 +1242,7 @@ fn infer_placeholder_type(
.emit();
}
None => {
let mut diag = bad_placeholder_type(tcx, span);
let mut diag = bad_placeholder_type(tcx, vec![span]);
if ty != tcx.types.err {
diag.span_suggestion(
span,
@ -1183,7 +1273,7 @@ fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
}
TraitItemKind::Const(ref ty, body_id) => body_id
.and_then(|body_id| {
if let hir::TyKind::Infer = ty.kind {
if is_suggestable_infer_ty(ty) {
Some(infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident))
} else {
None
@ -1202,7 +1292,7 @@ fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
tcx.mk_fn_def(def_id, substs)
}
ImplItemKind::Const(ref ty, body_id) => {
if let hir::TyKind::Infer = ty.kind {
if is_suggestable_infer_ty(ty) {
infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident)
} else {
icx.to_ty(ty)
@ -1227,7 +1317,7 @@ fn type_of(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
Node::Item(item) => {
match item.kind {
ItemKind::Static(ref ty, .., body_id) | ItemKind::Const(ref ty, body_id) => {
if let hir::TyKind::Infer = ty.kind {
if is_suggestable_infer_ty(ty) {
infer_placeholder_type(tcx, def_id, body_id, ty.span, item.ident)
} else {
icx.to_ty(ty)
@ -1699,9 +1789,20 @@ fn find_opaque_ty_constraints(tcx: TyCtxt<'_>, def_id: DefId) -> Ty<'_> {
}
}
/// Whether `ty` is a type with `_` placeholders that can be infered. Used in diagnostics only to
/// use inference to provide suggestions for the appropriate type if possible.
fn is_suggestable_infer_ty(ty: &hir::Ty<'_>) -> bool {
match &ty.kind {
hir::TyKind::Infer => true,
hir::TyKind::Slice(ty) | hir::TyKind::Array(ty, _) => is_suggestable_infer_ty(ty),
hir::TyKind::Tup(tys) => tys.iter().any(|ty| is_suggestable_infer_ty(ty)),
_ => false,
}
}
pub fn get_infer_ret_ty(output: &'hir hir::FunctionRetTy<'hir>) -> Option<&'hir hir::Ty<'hir>> {
if let hir::FunctionRetTy::Return(ref ty) = output {
if let hir::TyKind::Infer = ty.kind {
if is_suggestable_infer_ty(ty) {
return Some(&**ty);
}
}
@ -1719,19 +1820,23 @@ fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
match tcx.hir().get(hir_id) {
TraitItem(hir::TraitItem {
kind: TraitItemKind::Method(sig, TraitMethod::Provided(_)),
ident,
generics,
..
})
| ImplItem(hir::ImplItem { kind: ImplItemKind::Method(sig, _), .. })
| Item(hir::Item { kind: ItemKind::Fn(sig, _, _), .. }) => {
| ImplItem(hir::ImplItem { kind: ImplItemKind::Method(sig, _), ident, generics, .. })
| Item(hir::Item { kind: ItemKind::Fn(sig, generics, _), ident, .. }) => {
match get_infer_ret_ty(&sig.decl.output) {
Some(ty) => {
let fn_sig = tcx.typeck_tables_of(def_id).liberated_fn_sigs()[hir_id];
let mut diag = bad_placeholder_type(tcx, ty.span);
let mut visitor = PlaceholderHirTyCollector::default();
visitor.visit_ty(ty);
let mut diag = bad_placeholder_type(tcx, visitor.0);
let ret_ty = fn_sig.output();
if ret_ty != tcx.types.err {
diag.span_suggestion(
ty.span,
"replace `_` with the correct return type",
"replace with the correct return type",
ret_ty.to_string(),
Applicability::MaybeIncorrect,
);
@ -1739,14 +1844,30 @@ fn fn_sig(tcx: TyCtxt<'_>, def_id: DefId) -> ty::PolyFnSig<'_> {
diag.emit();
ty::Binder::bind(fn_sig)
}
None => AstConv::ty_of_fn(&icx, sig.header.unsafety, sig.header.abi, &sig.decl),
None => AstConv::ty_of_fn(
&icx,
sig.header.unsafety,
sig.header.abi,
&sig.decl,
&generics.params[..],
Some(ident.span),
),
}
}
TraitItem(hir::TraitItem {
kind: TraitItemKind::Method(FnSig { header, decl }, _),
ident,
generics,
..
}) => AstConv::ty_of_fn(&icx, header.unsafety, header.abi, decl),
}) => AstConv::ty_of_fn(
&icx,
header.unsafety,
header.abi,
decl,
&generics.params[..],
Some(ident.span),
),
ForeignItem(&hir::ForeignItem { kind: ForeignItemKind::Fn(ref fn_decl, _, _), .. }) => {
let abi = tcx.hir().get_foreign_abi(hir_id);
@ -2351,7 +2472,7 @@ fn compute_sig_of_foreign_fn_decl<'tcx>(
} else {
hir::Unsafety::Unsafe
};
let fty = AstConv::ty_of_fn(&ItemCtxt::new(tcx, def_id), unsafety, abi, decl);
let fty = AstConv::ty_of_fn(&ItemCtxt::new(tcx, def_id), unsafety, abi, decl, &[], None);
// Feature gate SIMD types in FFI, since I am not sure that the
// ABIs are handled at all correctly. -huonw