From 96f5584b808cd08c3c8208db4fee04d2c2b71d79 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Sun, 19 Apr 2020 16:52:15 -0700
Subject: [PATCH 1/2] Expand "recursive opaque type" diagnostic
Fix #70968, partially address #66523.
---
src/librustc_hir/hir.rs | 12 ++
.../traits/error_reporting/suggestions.rs | 4 +-
src/librustc_typeck/check/mod.rs | 195 ++++++++++++++++--
.../ui/impl-trait/binding-without-value.rs | 9 +
.../impl-trait/binding-without-value.stderr | 16 ++
.../issues/infinite-impl-trait-issue-38064.rs | 4 +-
.../infinite-impl-trait-issue-38064.stderr | 24 ++-
.../recursive-impl-trait-type-direct.stderr | 9 +-
.../recursive-impl-trait-type-indirect.stderr | 153 ++++++++------
...e-impl-trait-type-through-non-recursive.rs | 8 +-
...pl-trait-type-through-non-recursive.stderr | 44 ++--
src/test/ui/impl-trait/where-allowed-2.rs | 3 +-
src/test/ui/impl-trait/where-allowed-2.stderr | 8 +-
13 files changed, 374 insertions(+), 115 deletions(-)
create mode 100644 src/test/ui/impl-trait/binding-without-value.rs
create mode 100644 src/test/ui/impl-trait/binding-without-value.stderr
diff --git a/src/librustc_hir/hir.rs b/src/librustc_hir/hir.rs
index 634ab32a28542..bed2044c70855 100644
--- a/src/librustc_hir/hir.rs
+++ b/src/librustc_hir/hir.rs
@@ -2726,6 +2726,18 @@ impl Node<'_> {
}
}
+ pub fn body_id(&self) -> Option<BodyId> {
+ match self {
+ Node::TraitItem(TraitItem {
+ kind: TraitItemKind::Fn(_, TraitFn::Provided(body_id)),
+ ..
+ })
+ | Node::ImplItem(ImplItem { kind: ImplItemKind::Fn(_, body_id), .. })
+ | Node::Item(Item { kind: ItemKind::Fn(.., body_id), .. }) => Some(*body_id),
+ _ => None,
+ }
+ }
+
pub fn generics(&self) -> Option<&Generics<'_>> {
match self {
Node::TraitItem(TraitItem { generics, .. })
diff --git a/src/librustc_trait_selection/traits/error_reporting/suggestions.rs b/src/librustc_trait_selection/traits/error_reporting/suggestions.rs
index 8796cfb52165d..edff67929f6d0 100644
--- a/src/librustc_trait_selection/traits/error_reporting/suggestions.rs
+++ b/src/librustc_trait_selection/traits/error_reporting/suggestions.rs
@@ -1992,8 +1992,8 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
/// Collect all the returned expressions within the input expression.
/// Used to point at the return spans when we want to suggest some change to them.
#[derive(Default)]
-struct ReturnsVisitor<'v> {
- returns: Vec<&'v hir::Expr<'v>>,
+pub struct ReturnsVisitor<'v> {
+ pub returns: Vec<&'v hir::Expr<'v>>,
in_block_tail: bool,
}
diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs
index a409e20953da1..d4db32abe2a16 100644
--- a/src/librustc_typeck/check/mod.rs
+++ b/src/librustc_typeck/check/mod.rs
@@ -138,6 +138,7 @@ use rustc_target::spec::abi::Abi;
use rustc_trait_selection::infer::InferCtxtExt as _;
use rustc_trait_selection::opaque_types::{InferCtxtExt as _, OpaqueTypeDecl};
use rustc_trait_selection::traits::error_reporting::recursive_type_with_infinite_size_error;
+use rustc_trait_selection::traits::error_reporting::suggestions::ReturnsVisitor;
use rustc_trait_selection::traits::error_reporting::InferCtxtExt as _;
use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _;
use rustc_trait_selection::traits::{
@@ -1711,6 +1712,181 @@ fn check_opaque_for_inheriting_lifetimes(tcx: TyCtxt<'tcx>, def_id: LocalDefId,
}
}
+/// Given a `DefId` for an opaque type in return position, find its parent item's return
+/// expressions.
+fn get_owner_return_paths(
+ tcx: TyCtxt<'tcx>,
+ def_id: LocalDefId,
+) -> Option<(hir::HirId, ReturnsVisitor<'tcx>)> {
+ let hir_id = tcx.hir().as_local_hir_id(def_id);
+ let id = tcx.hir().get_parent_item(hir_id);
+ tcx.hir()
+ .find(id)
+ .map(|n| (id, n))
+ .and_then(|(hir_id, node)| node.body_id().map(|b| (hir_id, b)))
+ .map(|(hir_id, body_id)| {
+ let body = tcx.hir().body(body_id);
+ let mut visitor = ReturnsVisitor::default();
+ visitor.visit_body(body);
+ (hir_id, visitor)
+ })
+}
+
+/// Emit an error for recursive opaque types.
+///
+/// If this is a return `impl Trait`, find the item's return expressions and point at them. For
+/// direct recursion this is enough, but for indirect recursion also point at the last intermediary
+/// `impl Trait`.
+///
+/// If all the return expressions evaluate to `!`, then we explain that the error will go away
+/// after changing it. This can happen when a user uses `panic!()` or similar as a placeholder.
+fn opaque_type_cycle_error(tcx: TyCtxt<'tcx>, def_id: LocalDefId, span: Span) {
+ let mut err =
+ struct_span_err!(tcx.sess, span, E0720, "cannot resolve opaque type to a concrete type");
+
+ let mut label = false;
+ if let Some((hir_id, visitor)) = get_owner_return_paths(tcx, def_id) {
+ let tables = tcx.typeck_tables_of(tcx.hir().local_def_id(hir_id));
+ if visitor
+ .returns
+ .iter()
+ .filter_map(|expr| tables.node_type_opt(expr.hir_id))
+ .map(|ty| tcx.infer_ctxt().enter(|infcx| infcx.resolve_vars_if_possible(&ty)))
+ .all(|ty| matches!(ty.kind, ty::Never))
+ {
+ let spans = visitor
+ .returns
+ .iter()
+ .filter(|expr| tables.node_type_opt(expr.hir_id).is_some())
+ .map(|expr| expr.span)
+ .collect::<Vec<Span>>();
+ let span_len = spans.len();
+ if span_len == 1 {
+ err.span_label(spans[0], "this returned value is of `!` type");
+ } else {
+ let mut multispan: MultiSpan = spans.clone().into();
+ for span in spans {
+ multispan
+ .push_span_label(span, "this returned value is of `!` type".to_string());
+ }
+ err.span_note(multispan, "these returned values have a concrete \"never\" type");
+ }
+ err.help("this error will resolve once the item's body returns a concrete type");
+ } else {
+ let mut seen = FxHashSet::default();
+ seen.insert(span);
+ err.span_label(span, "recursive opaque type");
+ label = true;
+ for (sp, ty) in visitor
+ .returns
+ .iter()
+ .filter_map(|e| tables.node_type_opt(e.hir_id).map(|t| (e.span, t)))
+ .filter(|(_, ty)| !matches!(ty.kind, ty::Never))
+ .map(|(sp, ty)| {
+ (sp, tcx.infer_ctxt().enter(|infcx| infcx.resolve_vars_if_possible(&ty)))
+ })
+ {
+ struct VisitTypes(Vec<DefId>);
+ impl<'tcx> ty::fold::TypeVisitor<'tcx> for VisitTypes {
+ fn visit_ty(&mut self, t: Ty<'tcx>) -> bool {
+ match t.kind {
+ ty::Opaque(def, _) => {
+ self.0.push(def);
+ false
+ }
+ _ => t.super_visit_with(self),
+ }
+ }
+ }
+ let mut visitor = VisitTypes(vec![]);
+ ty.visit_with(&mut visitor);
+ for def_id in visitor.0 {
+ let ty_span = tcx.def_span(def_id);
+ if !seen.contains(&ty_span) {
+ err.span_label(ty_span, &format!("returning this opaque type `{}`", ty));
+ seen.insert(ty_span);
+ }
+ err.span_label(sp, &format!("returning here with type `{}`", ty));
+ }
+ }
+ }
+ }
+ if !label {
+ err.span_label(span, "cannot resolve to a concrete type");
+ }
+ err.emit();
+}
+
+/// Emit an error for recursive opaque types in a `let` binding.
+fn binding_opaque_type_cycle_error(
+ tcx: TyCtxt<'tcx>,
+ def_id: LocalDefId,
+ span: Span,
+ partially_expanded_type: Ty<'tcx>,
+) {
+ let mut err =
+ struct_span_err!(tcx.sess, span, E0720, "cannot resolve opaque type to a concrete type");
+ err.span_label(span, "cannot resolve to a concrete type");
+ let hir_id = tcx.hir().as_local_hir_id(def_id);
+ let mut prev_hir_id = hir_id;
+ let mut hir_id = tcx.hir().get_parent_node(hir_id);
+ while let Some(node) = tcx.hir().find(hir_id) {
+ match node {
+ hir::Node::Local(hir::Local {
+ pat,
+ init: None,
+ ty: Some(ty),
+ source: hir::LocalSource::Normal,
+ ..
+ }) => {
+ err.span_label(pat.span, "this binding might not have a concrete type");
+ err.span_suggestion_verbose(
+ ty.span.shrink_to_hi(),
+ "set the binding to a value for a concrete type to be resolved",
+ " = /* value */".to_string(),
+ Applicability::HasPlaceholders,
+ );
+ }
+ hir::Node::Local(hir::Local {
+ init: Some(expr),
+ source: hir::LocalSource::Normal,
+ ..
+ }) => {
+ let hir_id = tcx.hir().as_local_hir_id(def_id);
+ let tables =
+ tcx.typeck_tables_of(tcx.hir().local_def_id(tcx.hir().get_parent_item(hir_id)));
+ let ty = tables.node_type_opt(expr.hir_id);
+ if let Some(ty) =
+ tcx.infer_ctxt().enter(|infcx| infcx.resolve_vars_if_possible(&ty))
+ {
+ err.span_label(
+ expr.span,
+ &format!(
+ "this is of type `{}`, which doesn't constrain \
+ `{}` enough to arrive to a concrete type",
+ ty, partially_expanded_type
+ ),
+ );
+ }
+ }
+ _ => {}
+ }
+ if prev_hir_id == hir_id {
+ break;
+ }
+ prev_hir_id = hir_id;
+ hir_id = tcx.hir().get_parent_node(hir_id);
+ }
+ err.emit();
+}
+
+fn async_opaque_type_cycle_error(tcx: TyCtxt<'tcx>, span: Span) {
+ struct_span_err!(tcx.sess, span, E0733, "recursion in an `async fn` requires boxing")
+ .span_label(span, "recursive `async fn`")
+ .note("a recursive `async fn` must be rewritten to return a boxed `dyn Future`")
+ .emit();
+}
+
/// Checks that an opaque type does not contain cycles.
fn check_opaque_for_cycles<'tcx>(
tcx: TyCtxt<'tcx>,
@@ -1721,21 +1897,12 @@ fn check_opaque_for_cycles<'tcx>(
) {
if let Err(partially_expanded_type) = tcx.try_expand_impl_trait_type(def_id.to_def_id(), substs)
{
- if let hir::OpaqueTyOrigin::AsyncFn = origin {
- struct_span_err!(tcx.sess, span, E0733, "recursion in an `async fn` requires boxing",)
- .span_label(span, "recursive `async fn`")
- .note("a recursive `async fn` must be rewritten to return a boxed `dyn Future`")
- .emit();
- } else {
- let mut err =
- struct_span_err!(tcx.sess, span, E0720, "opaque type expands to a recursive type",);
- err.span_label(span, "expands to a recursive type");
- if let ty::Opaque(..) = partially_expanded_type.kind {
- err.note("type resolves to itself");
- } else {
- err.note(&format!("expanded type is `{}`", partially_expanded_type));
+ match origin {
+ hir::OpaqueTyOrigin::AsyncFn => async_opaque_type_cycle_error(tcx, span),
+ hir::OpaqueTyOrigin::Binding => {
+ binding_opaque_type_cycle_error(tcx, def_id, span, partially_expanded_type)
}
- err.emit();
+ _ => opaque_type_cycle_error(tcx, def_id, span),
}
}
}
diff --git a/src/test/ui/impl-trait/binding-without-value.rs b/src/test/ui/impl-trait/binding-without-value.rs
new file mode 100644
index 0000000000000..6a97f28ff552b
--- /dev/null
+++ b/src/test/ui/impl-trait/binding-without-value.rs
@@ -0,0 +1,9 @@
+#![allow(incomplete_features)]
+#![feature(impl_trait_in_bindings)]
+
+fn foo() {
+ let _ : impl Copy;
+ //~^ ERROR cannot resolve opaque type
+}
+
+fn main() {}
diff --git a/src/test/ui/impl-trait/binding-without-value.stderr b/src/test/ui/impl-trait/binding-without-value.stderr
new file mode 100644
index 0000000000000..1898af5b63eeb
--- /dev/null
+++ b/src/test/ui/impl-trait/binding-without-value.stderr
@@ -0,0 +1,16 @@
+error[E0720]: cannot resolve opaque type to a concrete type
+ --> $DIR/binding-without-value.rs:5:13
+ |
+LL | let _ : impl Copy;
+ | - ^^^^^^^^^ cannot resolve to a concrete type
+ | |
+ | this binding might not have a concrete type
+ |
+help: set the binding to a value for a concrete type to be resolved
+ |
+LL | let _ : impl Copy = /* value */;
+ | ^^^^^^^^^^^^^
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0720`.
diff --git a/src/test/ui/impl-trait/issues/infinite-impl-trait-issue-38064.rs b/src/test/ui/impl-trait/issues/infinite-impl-trait-issue-38064.rs
index 150a8015cbc75..451ddb3cce0e0 100644
--- a/src/test/ui/impl-trait/issues/infinite-impl-trait-issue-38064.rs
+++ b/src/test/ui/impl-trait/issues/infinite-impl-trait-issue-38064.rs
@@ -5,13 +5,13 @@
trait Quux {}
-fn foo() -> impl Quux { //~ opaque type expands to a recursive type
+fn foo() -> impl Quux { //~ ERROR cannot resolve opaque type
struct Foo<T>(T);
impl<T> Quux for Foo<T> {}
Foo(bar())
}
-fn bar() -> impl Quux { //~ opaque type expands to a recursive type
+fn bar() -> impl Quux { //~ ERROR cannot resolve opaque type
struct Bar<T>(T);
impl<T> Quux for Bar<T> {}
Bar(foo())
diff --git a/src/test/ui/impl-trait/issues/infinite-impl-trait-issue-38064.stderr b/src/test/ui/impl-trait/issues/infinite-impl-trait-issue-38064.stderr
index d10001e8a8e53..a38fb7cb56e9d 100644
--- a/src/test/ui/impl-trait/issues/infinite-impl-trait-issue-38064.stderr
+++ b/src/test/ui/impl-trait/issues/infinite-impl-trait-issue-38064.stderr
@@ -1,18 +1,26 @@
-error[E0720]: opaque type expands to a recursive type
+error[E0720]: cannot resolve opaque type to a concrete type
--> $DIR/infinite-impl-trait-issue-38064.rs:8:13
|
LL | fn foo() -> impl Quux {
- | ^^^^^^^^^ expands to a recursive type
- |
- = note: expanded type is `foo::Foo<bar::Bar<impl Quux>>`
+ | ^^^^^^^^^ recursive opaque type
+...
+LL | Foo(bar())
+ | ---------- returning here with type `foo::Foo<impl Quux>`
+...
+LL | fn bar() -> impl Quux {
+ | --------- returning this opaque type `foo::Foo<impl Quux>`
-error[E0720]: opaque type expands to a recursive type
+error[E0720]: cannot resolve opaque type to a concrete type
--> $DIR/infinite-impl-trait-issue-38064.rs:14:13
|
+LL | fn foo() -> impl Quux {
+ | --------- returning this opaque type `bar::Bar<impl Quux>`
+...
LL | fn bar() -> impl Quux {
- | ^^^^^^^^^ expands to a recursive type
- |
- = note: expanded type is `bar::Bar<foo::Foo<impl Quux>>`
+ | ^^^^^^^^^ recursive opaque type
+...
+LL | Bar(foo())
+ | ---------- returning here with type `bar::Bar<impl Quux>`
error: aborting due to 2 previous errors
diff --git a/src/test/ui/impl-trait/recursive-impl-trait-type-direct.stderr b/src/test/ui/impl-trait/recursive-impl-trait-type-direct.stderr
index 5a95e2969d1b0..5149d42370c75 100644
--- a/src/test/ui/impl-trait/recursive-impl-trait-type-direct.stderr
+++ b/src/test/ui/impl-trait/recursive-impl-trait-type-direct.stderr
@@ -1,10 +1,11 @@
-error[E0720]: opaque type expands to a recursive type
+error[E0720]: cannot resolve opaque type to a concrete type
--> $DIR/recursive-impl-trait-type-direct.rs:5:14
|
LL | fn test() -> impl Sized {
- | ^^^^^^^^^^ expands to a recursive type
- |
- = note: type resolves to itself
+ | ^^^^^^^^^^ recursive opaque type
+LL |
+LL | test()
+ | ------ returning here with type `impl Sized`
error: aborting due to previous error
diff --git a/src/test/ui/impl-trait/recursive-impl-trait-type-indirect.stderr b/src/test/ui/impl-trait/recursive-impl-trait-type-indirect.stderr
index 6573b00870c5b..0bf362e9a6d4a 100644
--- a/src/test/ui/impl-trait/recursive-impl-trait-type-indirect.stderr
+++ b/src/test/ui/impl-trait/recursive-impl-trait-type-indirect.stderr
@@ -1,114 +1,147 @@
-error[E0720]: opaque type expands to a recursive type
+error[E0720]: cannot resolve opaque type to a concrete type
--> $DIR/recursive-impl-trait-type-indirect.rs:7:22
|
LL | fn option(i: i32) -> impl Sized {
- | ^^^^^^^^^^ expands to a recursive type
- |
- = note: expanded type is `std::option::Option<(impl Sized, i32)>`
+ | ^^^^^^^^^^ recursive opaque type
+LL |
+LL | if i < 0 { None } else { Some((option(i - 1), i)) }
+ | ---- ------------------------ returning here with type `std::option::Option<(impl Sized, i32)>`
+ | |
+ | returning here with type `std::option::Option<(impl Sized, i32)>`
-error[E0720]: opaque type expands to a recursive type
+error[E0720]: cannot resolve opaque type to a concrete type
--> $DIR/recursive-impl-trait-type-indirect.rs:12:15
|
LL | fn tuple() -> impl Sized {
- | ^^^^^^^^^^ expands to a recursive type
- |
- = note: expanded type is `(impl Sized,)`
+ | ^^^^^^^^^^ recursive opaque type
+LL |
+LL | (tuple(),)
+ | ---------- returning here with type `(impl Sized,)`
-error[E0720]: opaque type expands to a recursive type
+error[E0720]: cannot resolve opaque type to a concrete type
--> $DIR/recursive-impl-trait-type-indirect.rs:17:15
|
LL | fn array() -> impl Sized {
- | ^^^^^^^^^^ expands to a recursive type
- |
- = note: expanded type is `[impl Sized; 1]`
+ | ^^^^^^^^^^ recursive opaque type
+LL |
+LL | [array()]
+ | --------- returning here with type `[impl Sized; 1]`
-error[E0720]: opaque type expands to a recursive type
+error[E0720]: cannot resolve opaque type to a concrete type
--> $DIR/recursive-impl-trait-type-indirect.rs:22:13
|
LL | fn ptr() -> impl Sized {
- | ^^^^^^^^^^ expands to a recursive type
- |
- = note: expanded type is `*const impl Sized`
+ | ^^^^^^^^^^ recursive opaque type
+LL |
+LL | &ptr() as *const _
+ | ------------------ returning here with type `*const impl Sized`
-error[E0720]: opaque type expands to a recursive type
+error[E0720]: cannot resolve opaque type to a concrete type
--> $DIR/recursive-impl-trait-type-indirect.rs:27:16
|
LL | fn fn_ptr() -> impl Sized {
- | ^^^^^^^^^^ expands to a recursive type
- |
- = note: expanded type is `fn() -> impl Sized`
+ | ^^^^^^^^^^ recursive opaque type
+LL |
+LL | fn_ptr as fn() -> _
+ | ------------------- returning here with type `fn() -> impl Sized`
-error[E0720]: opaque type expands to a recursive type
+error[E0720]: cannot resolve opaque type to a concrete type
--> $DIR/recursive-impl-trait-type-indirect.rs:32:25
|
-LL | fn closure_capture() -> impl Sized {
- | ^^^^^^^^^^ expands to a recursive type
- |
- = note: expanded type is `[closure@$DIR/recursive-impl-trait-type-indirect.rs:35:5: 37:6 x:impl Sized]`
+LL | fn closure_capture() -> impl Sized {
+ | ^^^^^^^^^^ recursive opaque type
+...
+LL | / move || {
+LL | | x;
+LL | | }
+ | |_____- returning here with type `[closure@$DIR/recursive-impl-trait-type-indirect.rs:35:5: 37:6 x:impl Sized]`
-error[E0720]: opaque type expands to a recursive type
+error[E0720]: cannot resolve opaque type to a concrete type
--> $DIR/recursive-impl-trait-type-indirect.rs:40:29
|
-LL | fn closure_ref_capture() -> impl Sized {
- | ^^^^^^^^^^ expands to a recursive type
- |
- = note: expanded type is `[closure@$DIR/recursive-impl-trait-type-indirect.rs:43:5: 45:6 x:impl Sized]`
+LL | fn closure_ref_capture() -> impl Sized {
+ | ^^^^^^^^^^ recursive opaque type
+...
+LL | / move || {
+LL | | &x;
+LL | | }
+ | |_____- returning here with type `[closure@$DIR/recursive-impl-trait-type-indirect.rs:43:5: 45:6 x:impl Sized]`
-error[E0720]: opaque type expands to a recursive type
+error[E0720]: cannot resolve opaque type to a concrete type
--> $DIR/recursive-impl-trait-type-indirect.rs:48:21
|
LL | fn closure_sig() -> impl Sized {
- | ^^^^^^^^^^ expands to a recursive type
- |
- = note: expanded type is `[closure@$DIR/recursive-impl-trait-type-indirect.rs:50:5: 50:21]`
+ | ^^^^^^^^^^ recursive opaque type
+LL |
+LL | || closure_sig()
+ | ---------------- returning here with type `[closure@$DIR/recursive-impl-trait-type-indirect.rs:50:5: 50:21]`
-error[E0720]: opaque type expands to a recursive type
+error[E0720]: cannot resolve opaque type to a concrete type
--> $DIR/recursive-impl-trait-type-indirect.rs:53:23
|
LL | fn generator_sig() -> impl Sized {
- | ^^^^^^^^^^ expands to a recursive type
- |
- = note: expanded type is `[closure@$DIR/recursive-impl-trait-type-indirect.rs:55:5: 55:23]`
+ | ^^^^^^^^^^ recursive opaque type
+LL |
+LL | || generator_sig()
+ | ------------------ returning here with type `[closure@$DIR/recursive-impl-trait-type-indirect.rs:55:5: 55:23]`
-error[E0720]: opaque type expands to a recursive type
+error[E0720]: cannot resolve opaque type to a concrete type
--> $DIR/recursive-impl-trait-type-indirect.rs:58:27
|
-LL | fn generator_capture() -> impl Sized {
- | ^^^^^^^^^^ expands to a recursive type
- |
- = note: expanded type is `[generator@$DIR/recursive-impl-trait-type-indirect.rs:61:5: 64:6 x:impl Sized {()}]`
+LL | fn generator_capture() -> impl Sized {
+ | ^^^^^^^^^^ recursive opaque type
+...
+LL | / move || {
+LL | | yield;
+LL | | x;
+LL | | }
+ | |_____- returning here with type `[generator@$DIR/recursive-impl-trait-type-indirect.rs:61:5: 64:6 x:impl Sized {()}]`
-error[E0720]: opaque type expands to a recursive type
+error[E0720]: cannot resolve opaque type to a concrete type
--> $DIR/recursive-impl-trait-type-indirect.rs:67:35
|
LL | fn substs_change<T: 'static>() -> impl Sized {
- | ^^^^^^^^^^ expands to a recursive type
- |
- = note: expanded type is `(impl Sized,)`
+ | ^^^^^^^^^^ recursive opaque type
+LL |
+LL | (substs_change::<&T>(),)
+ | ------------------------ returning here with type `(impl Sized,)`
-error[E0720]: opaque type expands to a recursive type
+error[E0720]: cannot resolve opaque type to a concrete type
--> $DIR/recursive-impl-trait-type-indirect.rs:72:24
|
-LL | fn generator_hold() -> impl Sized {
- | ^^^^^^^^^^ expands to a recursive type
- |
- = note: expanded type is `[generator@$DIR/recursive-impl-trait-type-indirect.rs:74:5: 78:6 {impl Sized, ()}]`
+LL | fn generator_hold() -> impl Sized {
+ | ^^^^^^^^^^ recursive opaque type
+LL |
+LL | / move || {
+LL | | let x = generator_hold();
+LL | | yield;
+LL | | x;
+LL | | }
+ | |_____- returning here with type `[generator@$DIR/recursive-impl-trait-type-indirect.rs:74:5: 78:6 {impl Sized, ()}]`
-error[E0720]: opaque type expands to a recursive type
+error[E0720]: cannot resolve opaque type to a concrete type
--> $DIR/recursive-impl-trait-type-indirect.rs:86:26
|
LL | fn mutual_recursion() -> impl Sync {
- | ^^^^^^^^^ expands to a recursive type
- |
- = note: type resolves to itself
+ | ^^^^^^^^^ recursive opaque type
+LL |
+LL | mutual_recursion_b()
+ | -------------------- returning here with type `impl Sized`
+...
+LL | fn mutual_recursion_b() -> impl Sized {
+ | ---------- returning this opaque type `impl Sized`
-error[E0720]: opaque type expands to a recursive type
+error[E0720]: cannot resolve opaque type to a concrete type
--> $DIR/recursive-impl-trait-type-indirect.rs:91:28
|
+LL | fn mutual_recursion() -> impl Sync {
+ | --------- returning this opaque type `impl std::marker::Sync`
+...
LL | fn mutual_recursion_b() -> impl Sized {
- | ^^^^^^^^^^ expands to a recursive type
- |
- = note: type resolves to itself
+ | ^^^^^^^^^^ recursive opaque type
+LL |
+LL | mutual_recursion()
+ | ------------------ returning here with type `impl std::marker::Sync`
error: aborting due to 14 previous errors
diff --git a/src/test/ui/impl-trait/recursive-impl-trait-type-through-non-recursive.rs b/src/test/ui/impl-trait/recursive-impl-trait-type-through-non-recursive.rs
index cfd9c0ec5b45b..818e40365394d 100644
--- a/src/test/ui/impl-trait/recursive-impl-trait-type-through-non-recursive.rs
+++ b/src/test/ui/impl-trait/recursive-impl-trait-type-through-non-recursive.rs
@@ -4,21 +4,21 @@
fn id<T>(t: T) -> impl Sized { t }
-fn recursive_id() -> impl Sized { //~ ERROR opaque type expands to a recursive type
+fn recursive_id() -> impl Sized { //~ ERROR cannot resolve opaque type
id(recursive_id2())
}
-fn recursive_id2() -> impl Sized { //~ ERROR opaque type expands to a recursive type
+fn recursive_id2() -> impl Sized { //~ ERROR cannot resolve opaque type
id(recursive_id())
}
fn wrap<T>(t: T) -> impl Sized { (t,) }
-fn recursive_wrap() -> impl Sized { //~ ERROR opaque type expands to a recursive type
+fn recursive_wrap() -> impl Sized { //~ ERROR cannot resolve opaque type
wrap(recursive_wrap2())
}
-fn recursive_wrap2() -> impl Sized { //~ ERROR opaque type expands to a recursive type
+fn recursive_wrap2() -> impl Sized { //~ ERROR cannot resolve opaque type
wrap(recursive_wrap())
}
diff --git a/src/test/ui/impl-trait/recursive-impl-trait-type-through-non-recursive.stderr b/src/test/ui/impl-trait/recursive-impl-trait-type-through-non-recursive.stderr
index 73c12f6137d24..65e0b8882c425 100644
--- a/src/test/ui/impl-trait/recursive-impl-trait-type-through-non-recursive.stderr
+++ b/src/test/ui/impl-trait/recursive-impl-trait-type-through-non-recursive.stderr
@@ -1,34 +1,46 @@
-error[E0720]: opaque type expands to a recursive type
+error[E0720]: cannot resolve opaque type to a concrete type
--> $DIR/recursive-impl-trait-type-through-non-recursive.rs:7:22
|
+LL | fn id<T>(t: T) -> impl Sized { t }
+ | ---------- returning this opaque type `impl Sized`
+LL |
LL | fn recursive_id() -> impl Sized {
- | ^^^^^^^^^^ expands to a recursive type
- |
- = note: type resolves to itself
+ | ^^^^^^^^^^ recursive opaque type
+LL | id(recursive_id2())
+ | ------------------- returning here with type `impl Sized`
-error[E0720]: opaque type expands to a recursive type
+error[E0720]: cannot resolve opaque type to a concrete type
--> $DIR/recursive-impl-trait-type-through-non-recursive.rs:11:23
|
+LL | fn id<T>(t: T) -> impl Sized { t }
+ | ---------- returning this opaque type `impl Sized`
+...
LL | fn recursive_id2() -> impl Sized {
- | ^^^^^^^^^^ expands to a recursive type
- |
- = note: type resolves to itself
+ | ^^^^^^^^^^ recursive opaque type
+LL | id(recursive_id())
+ | ------------------ returning here with type `impl Sized`
-error[E0720]: opaque type expands to a recursive type
+error[E0720]: cannot resolve opaque type to a concrete type
--> $DIR/recursive-impl-trait-type-through-non-recursive.rs:17:24
|
+LL | fn wrap<T>(t: T) -> impl Sized { (t,) }
+ | ---------- returning this opaque type `impl Sized`
+LL |
LL | fn recursive_wrap() -> impl Sized {
- | ^^^^^^^^^^ expands to a recursive type
- |
- = note: expanded type is `((impl Sized,),)`
+ | ^^^^^^^^^^ recursive opaque type
+LL | wrap(recursive_wrap2())
+ | ----------------------- returning here with type `impl Sized`
-error[E0720]: opaque type expands to a recursive type
+error[E0720]: cannot resolve opaque type to a concrete type
--> $DIR/recursive-impl-trait-type-through-non-recursive.rs:21:25
|
+LL | fn wrap<T>(t: T) -> impl Sized { (t,) }
+ | ---------- returning this opaque type `impl Sized`
+...
LL | fn recursive_wrap2() -> impl Sized {
- | ^^^^^^^^^^ expands to a recursive type
- |
- = note: expanded type is `((impl Sized,),)`
+ | ^^^^^^^^^^ recursive opaque type
+LL | wrap(recursive_wrap())
+ | ---------------------- returning here with type `impl Sized`
error: aborting due to 4 previous errors
diff --git a/src/test/ui/impl-trait/where-allowed-2.rs b/src/test/ui/impl-trait/where-allowed-2.rs
index f7744ef1b3eae..462508f306ef3 100644
--- a/src/test/ui/impl-trait/where-allowed-2.rs
+++ b/src/test/ui/impl-trait/where-allowed-2.rs
@@ -3,7 +3,6 @@
use std::fmt::Debug;
// Disallowed
-fn in_adt_in_return() -> Vec<impl Debug> { panic!() }
-//~^ ERROR opaque type expands to a recursive type
+fn in_adt_in_return() -> Vec<impl Debug> { panic!() } //~ ERROR cannot resolve opaque type
fn main() {}
diff --git a/src/test/ui/impl-trait/where-allowed-2.stderr b/src/test/ui/impl-trait/where-allowed-2.stderr
index 1de15014c1f8d..6c0e0a4c9a38b 100644
--- a/src/test/ui/impl-trait/where-allowed-2.stderr
+++ b/src/test/ui/impl-trait/where-allowed-2.stderr
@@ -1,10 +1,12 @@
-error[E0720]: opaque type expands to a recursive type
+error[E0720]: cannot resolve opaque type to a concrete type
--> $DIR/where-allowed-2.rs:6:30
|
LL | fn in_adt_in_return() -> Vec<impl Debug> { panic!() }
- | ^^^^^^^^^^ expands to a recursive type
+ | ^^^^^^^^^^ -------- this returned value is of `!` type
+ | |
+ | cannot resolve to a concrete type
|
- = note: type resolves to itself
+ = help: this error will resolve once the item's body returns a concrete type
error: aborting due to previous error
From 8f12485335f506f4c9633305f323e55cdc3c8c2b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Esteban=20K=C3=BCber?= <esteban@kuber.com.ar>
Date: Mon, 15 Jun 2020 12:11:28 -0700
Subject: [PATCH 2/2] review comments
---
src/librustc_typeck/check/mod.rs | 22 +++++----------
.../impl-trait/binding-without-value.stderr | 4 +--
.../infinite-impl-trait-issue-38064.stderr | 4 +--
.../recursive-impl-trait-type-direct.stderr | 2 +-
.../recursive-impl-trait-type-indirect.stderr | 28 +++++++++----------
...pl-trait-type-through-non-recursive.stderr | 8 +++---
src/test/ui/impl-trait/where-allowed-2.stderr | 4 +--
7 files changed, 32 insertions(+), 40 deletions(-)
diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs
index d4db32abe2a16..1fff8fff9c03a 100644
--- a/src/librustc_typeck/check/mod.rs
+++ b/src/librustc_typeck/check/mod.rs
@@ -1741,8 +1741,7 @@ fn get_owner_return_paths(
/// If all the return expressions evaluate to `!`, then we explain that the error will go away
/// after changing it. This can happen when a user uses `panic!()` or similar as a placeholder.
fn opaque_type_cycle_error(tcx: TyCtxt<'tcx>, def_id: LocalDefId, span: Span) {
- let mut err =
- struct_span_err!(tcx.sess, span, E0720, "cannot resolve opaque type to a concrete type");
+ let mut err = struct_span_err!(tcx.sess, span, E0720, "cannot resolve opaque type");
let mut label = false;
if let Some((hir_id, visitor)) = get_owner_return_paths(tcx, def_id) {
@@ -1751,7 +1750,6 @@ fn opaque_type_cycle_error(tcx: TyCtxt<'tcx>, def_id: LocalDefId, span: Span) {
.returns
.iter()
.filter_map(|expr| tables.node_type_opt(expr.hir_id))
- .map(|ty| tcx.infer_ctxt().enter(|infcx| infcx.resolve_vars_if_possible(&ty)))
.all(|ty| matches!(ty.kind, ty::Never))
{
let spans = visitor
@@ -1782,9 +1780,6 @@ fn opaque_type_cycle_error(tcx: TyCtxt<'tcx>, def_id: LocalDefId, span: Span) {
.iter()
.filter_map(|e| tables.node_type_opt(e.hir_id).map(|t| (e.span, t)))
.filter(|(_, ty)| !matches!(ty.kind, ty::Never))
- .map(|(sp, ty)| {
- (sp, tcx.infer_ctxt().enter(|infcx| infcx.resolve_vars_if_possible(&ty)))
- })
{
struct VisitTypes(Vec<DefId>);
impl<'tcx> ty::fold::TypeVisitor<'tcx> for VisitTypes {
@@ -1812,7 +1807,7 @@ fn opaque_type_cycle_error(tcx: TyCtxt<'tcx>, def_id: LocalDefId, span: Span) {
}
}
if !label {
- err.span_label(span, "cannot resolve to a concrete type");
+ err.span_label(span, "cannot resolve opaque type");
}
err.emit();
}
@@ -1824,9 +1819,9 @@ fn binding_opaque_type_cycle_error(
span: Span,
partially_expanded_type: Ty<'tcx>,
) {
- let mut err =
- struct_span_err!(tcx.sess, span, E0720, "cannot resolve opaque type to a concrete type");
- err.span_label(span, "cannot resolve to a concrete type");
+ let mut err = struct_span_err!(tcx.sess, span, E0720, "cannot resolve opaque type");
+ err.span_label(span, "cannot resolve opaque type");
+ // Find the the owner that declared this `impl Trait` type.
let hir_id = tcx.hir().as_local_hir_id(def_id);
let mut prev_hir_id = hir_id;
let mut hir_id = tcx.hir().get_parent_node(hir_id);
@@ -1855,15 +1850,12 @@ fn binding_opaque_type_cycle_error(
let hir_id = tcx.hir().as_local_hir_id(def_id);
let tables =
tcx.typeck_tables_of(tcx.hir().local_def_id(tcx.hir().get_parent_item(hir_id)));
- let ty = tables.node_type_opt(expr.hir_id);
- if let Some(ty) =
- tcx.infer_ctxt().enter(|infcx| infcx.resolve_vars_if_possible(&ty))
- {
+ if let Some(ty) = tables.node_type_opt(expr.hir_id) {
err.span_label(
expr.span,
&format!(
"this is of type `{}`, which doesn't constrain \
- `{}` enough to arrive to a concrete type",
+ `{}` enough to arrive to a concrete type",
ty, partially_expanded_type
),
);
diff --git a/src/test/ui/impl-trait/binding-without-value.stderr b/src/test/ui/impl-trait/binding-without-value.stderr
index 1898af5b63eeb..0d2faeaf85d10 100644
--- a/src/test/ui/impl-trait/binding-without-value.stderr
+++ b/src/test/ui/impl-trait/binding-without-value.stderr
@@ -1,8 +1,8 @@
-error[E0720]: cannot resolve opaque type to a concrete type
+error[E0720]: cannot resolve opaque type
--> $DIR/binding-without-value.rs:5:13
|
LL | let _ : impl Copy;
- | - ^^^^^^^^^ cannot resolve to a concrete type
+ | - ^^^^^^^^^ cannot resolve opaque type
| |
| this binding might not have a concrete type
|
diff --git a/src/test/ui/impl-trait/issues/infinite-impl-trait-issue-38064.stderr b/src/test/ui/impl-trait/issues/infinite-impl-trait-issue-38064.stderr
index a38fb7cb56e9d..c538b77098a2d 100644
--- a/src/test/ui/impl-trait/issues/infinite-impl-trait-issue-38064.stderr
+++ b/src/test/ui/impl-trait/issues/infinite-impl-trait-issue-38064.stderr
@@ -1,4 +1,4 @@
-error[E0720]: cannot resolve opaque type to a concrete type
+error[E0720]: cannot resolve opaque type
--> $DIR/infinite-impl-trait-issue-38064.rs:8:13
|
LL | fn foo() -> impl Quux {
@@ -10,7 +10,7 @@ LL | Foo(bar())
LL | fn bar() -> impl Quux {
| --------- returning this opaque type `foo::Foo<impl Quux>`
-error[E0720]: cannot resolve opaque type to a concrete type
+error[E0720]: cannot resolve opaque type
--> $DIR/infinite-impl-trait-issue-38064.rs:14:13
|
LL | fn foo() -> impl Quux {
diff --git a/src/test/ui/impl-trait/recursive-impl-trait-type-direct.stderr b/src/test/ui/impl-trait/recursive-impl-trait-type-direct.stderr
index 5149d42370c75..5a3027ec751a9 100644
--- a/src/test/ui/impl-trait/recursive-impl-trait-type-direct.stderr
+++ b/src/test/ui/impl-trait/recursive-impl-trait-type-direct.stderr
@@ -1,4 +1,4 @@
-error[E0720]: cannot resolve opaque type to a concrete type
+error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-direct.rs:5:14
|
LL | fn test() -> impl Sized {
diff --git a/src/test/ui/impl-trait/recursive-impl-trait-type-indirect.stderr b/src/test/ui/impl-trait/recursive-impl-trait-type-indirect.stderr
index 0bf362e9a6d4a..75ff9e078cc2c 100644
--- a/src/test/ui/impl-trait/recursive-impl-trait-type-indirect.stderr
+++ b/src/test/ui/impl-trait/recursive-impl-trait-type-indirect.stderr
@@ -1,4 +1,4 @@
-error[E0720]: cannot resolve opaque type to a concrete type
+error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:7:22
|
LL | fn option(i: i32) -> impl Sized {
@@ -9,7 +9,7 @@ LL | if i < 0 { None } else { Some((option(i - 1), i)) }
| |
| returning here with type `std::option::Option<(impl Sized, i32)>`
-error[E0720]: cannot resolve opaque type to a concrete type
+error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:12:15
|
LL | fn tuple() -> impl Sized {
@@ -18,7 +18,7 @@ LL |
LL | (tuple(),)
| ---------- returning here with type `(impl Sized,)`
-error[E0720]: cannot resolve opaque type to a concrete type
+error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:17:15
|
LL | fn array() -> impl Sized {
@@ -27,7 +27,7 @@ LL |
LL | [array()]
| --------- returning here with type `[impl Sized; 1]`
-error[E0720]: cannot resolve opaque type to a concrete type
+error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:22:13
|
LL | fn ptr() -> impl Sized {
@@ -36,7 +36,7 @@ LL |
LL | &ptr() as *const _
| ------------------ returning here with type `*const impl Sized`
-error[E0720]: cannot resolve opaque type to a concrete type
+error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:27:16
|
LL | fn fn_ptr() -> impl Sized {
@@ -45,7 +45,7 @@ LL |
LL | fn_ptr as fn() -> _
| ------------------- returning here with type `fn() -> impl Sized`
-error[E0720]: cannot resolve opaque type to a concrete type
+error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:32:25
|
LL | fn closure_capture() -> impl Sized {
@@ -56,7 +56,7 @@ LL | | x;
LL | | }
| |_____- returning here with type `[closure@$DIR/recursive-impl-trait-type-indirect.rs:35:5: 37:6 x:impl Sized]`
-error[E0720]: cannot resolve opaque type to a concrete type
+error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:40:29
|
LL | fn closure_ref_capture() -> impl Sized {
@@ -67,7 +67,7 @@ LL | | &x;
LL | | }
| |_____- returning here with type `[closure@$DIR/recursive-impl-trait-type-indirect.rs:43:5: 45:6 x:impl Sized]`
-error[E0720]: cannot resolve opaque type to a concrete type
+error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:48:21
|
LL | fn closure_sig() -> impl Sized {
@@ -76,7 +76,7 @@ LL |
LL | || closure_sig()
| ---------------- returning here with type `[closure@$DIR/recursive-impl-trait-type-indirect.rs:50:5: 50:21]`
-error[E0720]: cannot resolve opaque type to a concrete type
+error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:53:23
|
LL | fn generator_sig() -> impl Sized {
@@ -85,7 +85,7 @@ LL |
LL | || generator_sig()
| ------------------ returning here with type `[closure@$DIR/recursive-impl-trait-type-indirect.rs:55:5: 55:23]`
-error[E0720]: cannot resolve opaque type to a concrete type
+error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:58:27
|
LL | fn generator_capture() -> impl Sized {
@@ -97,7 +97,7 @@ LL | | x;
LL | | }
| |_____- returning here with type `[generator@$DIR/recursive-impl-trait-type-indirect.rs:61:5: 64:6 x:impl Sized {()}]`
-error[E0720]: cannot resolve opaque type to a concrete type
+error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:67:35
|
LL | fn substs_change<T: 'static>() -> impl Sized {
@@ -106,7 +106,7 @@ LL |
LL | (substs_change::<&T>(),)
| ------------------------ returning here with type `(impl Sized,)`
-error[E0720]: cannot resolve opaque type to a concrete type
+error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:72:24
|
LL | fn generator_hold() -> impl Sized {
@@ -119,7 +119,7 @@ LL | | x;
LL | | }
| |_____- returning here with type `[generator@$DIR/recursive-impl-trait-type-indirect.rs:74:5: 78:6 {impl Sized, ()}]`
-error[E0720]: cannot resolve opaque type to a concrete type
+error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:86:26
|
LL | fn mutual_recursion() -> impl Sync {
@@ -131,7 +131,7 @@ LL | mutual_recursion_b()
LL | fn mutual_recursion_b() -> impl Sized {
| ---------- returning this opaque type `impl Sized`
-error[E0720]: cannot resolve opaque type to a concrete type
+error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-indirect.rs:91:28
|
LL | fn mutual_recursion() -> impl Sync {
diff --git a/src/test/ui/impl-trait/recursive-impl-trait-type-through-non-recursive.stderr b/src/test/ui/impl-trait/recursive-impl-trait-type-through-non-recursive.stderr
index 65e0b8882c425..fbc58837a8e94 100644
--- a/src/test/ui/impl-trait/recursive-impl-trait-type-through-non-recursive.stderr
+++ b/src/test/ui/impl-trait/recursive-impl-trait-type-through-non-recursive.stderr
@@ -1,4 +1,4 @@
-error[E0720]: cannot resolve opaque type to a concrete type
+error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-through-non-recursive.rs:7:22
|
LL | fn id<T>(t: T) -> impl Sized { t }
@@ -9,7 +9,7 @@ LL | fn recursive_id() -> impl Sized {
LL | id(recursive_id2())
| ------------------- returning here with type `impl Sized`
-error[E0720]: cannot resolve opaque type to a concrete type
+error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-through-non-recursive.rs:11:23
|
LL | fn id<T>(t: T) -> impl Sized { t }
@@ -20,7 +20,7 @@ LL | fn recursive_id2() -> impl Sized {
LL | id(recursive_id())
| ------------------ returning here with type `impl Sized`
-error[E0720]: cannot resolve opaque type to a concrete type
+error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-through-non-recursive.rs:17:24
|
LL | fn wrap<T>(t: T) -> impl Sized { (t,) }
@@ -31,7 +31,7 @@ LL | fn recursive_wrap() -> impl Sized {
LL | wrap(recursive_wrap2())
| ----------------------- returning here with type `impl Sized`
-error[E0720]: cannot resolve opaque type to a concrete type
+error[E0720]: cannot resolve opaque type
--> $DIR/recursive-impl-trait-type-through-non-recursive.rs:21:25
|
LL | fn wrap<T>(t: T) -> impl Sized { (t,) }
diff --git a/src/test/ui/impl-trait/where-allowed-2.stderr b/src/test/ui/impl-trait/where-allowed-2.stderr
index 6c0e0a4c9a38b..b8e06725cbcdd 100644
--- a/src/test/ui/impl-trait/where-allowed-2.stderr
+++ b/src/test/ui/impl-trait/where-allowed-2.stderr
@@ -1,10 +1,10 @@
-error[E0720]: cannot resolve opaque type to a concrete type
+error[E0720]: cannot resolve opaque type
--> $DIR/where-allowed-2.rs:6:30
|
LL | fn in_adt_in_return() -> Vec<impl Debug> { panic!() }
| ^^^^^^^^^^ -------- this returned value is of `!` type
| |
- | cannot resolve to a concrete type
+ | cannot resolve opaque type
|
= help: this error will resolve once the item's body returns a concrete type