Add more detail to type inference error
When encountering code where type inference fails, add more actionable
information:
```
fn main() {
let foo = Vec::new();
}
```
```
error[E0282]: type annotations needed for `std::vec::Vec<_>`
--> $DIR/vector-no-ann.rs:2:16
|
LL | let foo = Vec::new();
| --- ^^^^^^^^ cannot infer type for `T`
| |
| consider giving `foo` the type `std::vec::Vec<_>` with the type parameter `T` specified
```
We still need to modify type printing to optionally accept a
`TypeVariableTable` in order to properly print `std::vec::Vec<T>`.
CC #25633.
This commit is contained in:
Esteban Küber
parent
7840a0b753
commit
8bb094dac5
19 changed files with 82 additions and 42 deletions
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@ -15,17 +15,18 @@ struct FindLocalByTypeVisitor<'a, 'gcx: 'a + 'tcx, 'tcx: 'a> {
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hir_map: &'a hir::map::Map<'gcx>,
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found_local_pattern: Option<&'gcx Pat>,
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found_arg_pattern: Option<&'gcx Pat>,
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found_ty: Option<Ty<'tcx>>,
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}
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impl<'a, 'gcx, 'tcx> FindLocalByTypeVisitor<'a, 'gcx, 'tcx> {
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fn node_matches_type(&mut self, hir_id: HirId) -> bool {
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fn node_matches_type(&mut self, hir_id: HirId) -> Option<Ty<'tcx>> {
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let ty_opt = self.infcx.in_progress_tables.and_then(|tables| {
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tables.borrow().node_type_opt(hir_id)
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});
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match ty_opt {
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Some(ty) => {
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let ty = self.infcx.resolve_vars_if_possible(&ty);
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ty.walk().any(|inner_ty| {
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if ty.walk().any(|inner_ty| {
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inner_ty == self.target_ty || match (&inner_ty.sty, &self.target_ty.sty) {
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(&Infer(TyVar(a_vid)), &Infer(TyVar(b_vid))) => {
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self.infcx
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@ -35,9 +36,13 @@ impl<'a, 'gcx, 'tcx> FindLocalByTypeVisitor<'a, 'gcx, 'tcx> {
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}
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_ => false,
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}
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})
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}) {
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Some(ty)
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} else {
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None
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}
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}
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None => false,
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None => None,
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}
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}
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}
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@ -48,16 +53,21 @@ impl<'a, 'gcx, 'tcx> Visitor<'gcx> for FindLocalByTypeVisitor<'a, 'gcx, 'tcx> {
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}
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fn visit_local(&mut self, local: &'gcx Local) {
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if self.found_local_pattern.is_none() && self.node_matches_type(local.hir_id) {
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if let (None, Some(ty)) = (self.found_local_pattern, self.node_matches_type(local.hir_id)) {
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self.found_local_pattern = Some(&*local.pat);
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self.found_ty = Some(ty);
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}
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intravisit::walk_local(self, local);
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}
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fn visit_body(&mut self, body: &'gcx Body) {
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for argument in &body.arguments {
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if self.found_arg_pattern.is_none() && self.node_matches_type(argument.hir_id) {
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if let (None, Some(ty)) = (
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self.found_arg_pattern,
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self.node_matches_type(argument.hir_id),
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) {
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self.found_arg_pattern = Some(&*argument.pat);
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self.found_ty = Some(ty);
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}
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}
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intravisit::walk_body(self, body);
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@ -106,6 +116,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
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hir_map: &self.tcx.hir(),
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found_local_pattern: None,
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found_arg_pattern: None,
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found_ty: None,
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};
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if let Some(body_id) = body_id {
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@ -113,6 +124,10 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
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local_visitor.visit_expr(expr);
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}
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let ty_msg = match local_visitor.found_ty {
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Some(ty) if &ty.to_string() != "_" => format!(" for `{}`", ty),
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_ => String::new(),
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};
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if let Some(pattern) = local_visitor.found_arg_pattern {
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err_span = pattern.span;
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// We don't want to show the default label for closures.
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@ -131,13 +146,35 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
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// ^ consider giving this closure parameter a type
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// ```
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labels.clear();
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labels.push(
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(pattern.span, "consider giving this closure parameter a type".to_owned()));
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labels.push((pattern.span, format!(
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"consider giving this closure parameter {}",
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match local_visitor.found_ty {
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Some(ty) if &ty.to_string() != "_" => format!(
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"the type `{}` with the type parameter `{}` specified",
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ty,
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name,
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),
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_ => "a type".to_owned(),
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},
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)));
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} else if let Some(pattern) = local_visitor.found_local_pattern {
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if let Some(simple_ident) = pattern.simple_ident() {
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match pattern.span.compiler_desugaring_kind() {
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None => labels.push((pattern.span,
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format!("consider giving `{}` a type", simple_ident))),
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None => labels.push((
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pattern.span,
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format!(
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"consider giving `{}` {}",
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simple_ident,
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match local_visitor.found_ty {
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Some(ty) if &ty.to_string() != "_" => format!(
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"the type `{}` with the type parameter `{}` specified",
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ty,
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name,
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),
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_ => "a type".to_owned(),
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},
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),
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)),
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Some(CompilerDesugaringKind::ForLoop) => labels.push((
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pattern.span,
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"the element type for this iterator is not specified".to_owned(),
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@ -147,12 +184,15 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
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} else {
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labels.push((pattern.span, "consider giving the pattern a type".to_owned()));
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}
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}
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};
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let mut err = struct_span_err!(self.tcx.sess,
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err_span,
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E0282,
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"type annotations needed");
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let mut err = struct_span_err!(
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self.tcx.sess,
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err_span,
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E0282,
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"type annotations needed{}",
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ty_msg,
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);
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for (target_span, label_message) in labels {
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err.span_label(target_span, label_message);
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@ -4,5 +4,5 @@ fn new<T>() -> &'static T {
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fn main() {
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let &v = new();
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//~^ ERROR type annotations needed [E0282]
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//~^ ERROR type annotations needed
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}
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@ -1,4 +1,4 @@
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error[E0282]: type annotations needed
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error[E0282]: type annotations needed for `&_`
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--> $DIR/issue-12187-1.rs:6:10
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LL | let &v = new();
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@ -4,5 +4,5 @@ fn new<'r, T>() -> &'r T {
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fn main() {
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let &v = new();
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//~^ ERROR type annotations needed [E0282]
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//~^ ERROR type annotations needed
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}
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@ -1,4 +1,4 @@
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error[E0282]: type annotations needed
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error[E0282]: type annotations needed for `&_`
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--> $DIR/issue-12187-2.rs:6:10
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LL | let &v = new();
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@ -1,10 +1,10 @@
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error[E0282]: type annotations needed
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error[E0282]: type annotations needed for `B<_>`
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--> $DIR/issue-17551.rs:6:15
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LL | let foo = B(marker::PhantomData);
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| --- ^ cannot infer type for `T`
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| consider giving `foo` a type
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| consider giving `foo` the type `B<_>` with the type parameter `T` specified
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error: aborting due to previous error
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@ -1,4 +1,4 @@
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error[E0282]: type annotations needed
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error[E0282]: type annotations needed for `&(_,)`
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--> $DIR/issue-20261.rs:4:11
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LL | for (ref i,) in [].iter() {
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@ -1,8 +1,8 @@
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error[E0282]: type annotations needed
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error[E0282]: type annotations needed for `Expr<'_, _>`
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--> $DIR/issue-23046.rs:17:15
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LL | let ex = |x| {
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| ^ consider giving this closure parameter a type
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| ^ consider giving this closure parameter the type `Expr<'_, _>` with the type parameter `VAR` specified
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error: aborting due to previous error
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@ -1,4 +1,4 @@
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error[E0282]: type annotations needed
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error[E0282]: type annotations needed for `(std::sync::mpsc::Sender<Foo<_>>, std::sync::mpsc::Receiver<Foo<_>>)`
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--> $DIR/issue-25368.rs:11:17
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LL | let (tx, rx) = channel();
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@ -1,10 +1,10 @@
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error[E0282]: type annotations needed
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error[E0282]: type annotations needed for `&[_; 0]`
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--> $DIR/issue-7813.rs:2:13
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LL | let v = &[];
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| - ^^^ cannot infer type
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| |
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| consider giving `v` a type
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| consider giving `v` the type `&[_; 0]` with the type parameter `_` specified
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error: aborting due to previous error
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@ -22,7 +22,7 @@ impl Foo for Vec<isize> {
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fn m1() {
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// we couldn't infer the type of the vector just based on calling foo()...
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let mut x = Vec::new();
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//~^ ERROR type annotations needed [E0282]
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//~^ ERROR type annotations needed
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x.foo();
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}
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@ -1,10 +1,10 @@
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error[E0282]: type annotations needed
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error[E0282]: type annotations needed for `std::vec::Vec<_>`
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--> $DIR/method-ambig-one-trait-unknown-int-type.rs:24:17
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LL | let mut x = Vec::new();
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| ----- ^^^^^^^^ cannot infer type for `T`
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| |
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| consider giving `x` a type
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| consider giving `x` the type `std::vec::Vec<_>` with the type parameter `T` specified
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error[E0308]: mismatched types
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--> $DIR/method-ambig-one-trait-unknown-int-type.rs:33:20
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@ -1,8 +1,8 @@
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error[E0282]: type annotations needed
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error[E0282]: type annotations needed for `std::option::Option<_>`
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--> $DIR/issue-42234-unknown-receiver-type.rs:7:5
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LL | let x: Option<_> = None;
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| - consider giving `x` a type
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| - consider giving `x` the type `std::option::Option<_>` with the type parameter `T` specified
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LL | x.unwrap().method_that_could_exist_on_some_type();
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| ^^^^^^^^^^ cannot infer type for `T`
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@ -1,10 +1,10 @@
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error[E0282]: type annotations needed
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error[E0282]: type annotations needed for `[_; 0]`
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--> $DIR/cannot_infer_local_or_array.rs:2:13
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LL | let x = [];
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| - ^^ cannot infer type
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| |
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| consider giving `x` a type
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| consider giving `x` the type `[_; 0]` with the type parameter `_` specified
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error: aborting due to previous error
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@ -1,10 +1,10 @@
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error[E0282]: type annotations needed
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error[E0282]: type annotations needed for `std::vec::Vec<_>`
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--> $DIR/cannot_infer_local_or_vec.rs:2:13
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LL | let x = vec![];
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| - ^^^^^^ cannot infer type for `T`
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| |
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| consider giving `x` a type
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| consider giving `x` the type `std::vec::Vec<_>` with the type parameter `T` specified
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= note: this error originates in a macro outside of the current crate (in Nightly builds, run with -Z external-macro-backtrace for more info)
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@ -1,4 +1,4 @@
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error[E0282]: type annotations needed
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error[E0282]: type annotations needed for `(std::vec::Vec<_>,)`
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--> $DIR/cannot_infer_local_or_vec_in_tuples.rs:2:18
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LL | let (x, ) = (vec![], );
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@ -1,8 +1,8 @@
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error[E0282]: type annotations needed
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error[E0282]: type annotations needed for `std::option::Option<_>`
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--> $DIR/unboxed-closures-failed-recursive-fn-2.rs:16:32
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LL | let mut closure0 = None;
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| ------------ consider giving `closure0` a type
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| ------------ consider giving `closure0` the type `std::option::Option<_>` with the type parameter `_` specified
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...
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LL | return c();
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| ^^^ cannot infer type
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@ -1,4 +1,4 @@
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fn main() {
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let _foo = Vec::new();
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//~^ ERROR type annotations needed [E0282]
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//~^ ERROR type annotations needed
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}
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@ -1,10 +1,10 @@
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error[E0282]: type annotations needed
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error[E0282]: type annotations needed for `std::vec::Vec<_>`
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--> $DIR/vector-no-ann.rs:2:16
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LL | let _foo = Vec::new();
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| ---- ^^^^^^^^ cannot infer type for `T`
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| |
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| consider giving `_foo` a type
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| consider giving `_foo` the type `std::vec::Vec<_>` with the type parameter `T` specified
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error: aborting due to previous error
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Loading…
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Reference in a new issue