Better comment for implicit captures

rust-lang · Mar 6, 2024 · fcf1367 · fcf1367
1 parent 62415e2
commit fcf1367
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Showing 10 changed files with 90 additions and 29 deletions.
diff --git a/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs b/compiler/rustc_hir_analysis/src/collect/resolve_bound_vars.rs
@@ -726,25 +726,62 @@ impl<'a, 'tcx> Visitor<'tcx> for BoundVarContext<'a, 'tcx> {
                     // Ensure that the parent of the def is an item, not HRTB
                     let parent_id = self.tcx.parent_hir_id(hir_id);
                     if !parent_id.is_owner() {
-                        struct_span_code_err!(
-                            self.tcx.dcx(),
-                            lifetime.ident.span,
-                            E0657,
-                            "`impl Trait` can only capture lifetimes bound at the fn or impl level"
-                        )
-                        .emit();
+                        // If the lifetime span is the same as the lifetime's declaration,
+                        // then it's likely we've implicitly captured the lifetime. Give
+                        // a better span and also note that it's implicitly captured.
+                        let diag = if lifetime.ident.span == self.tcx.def_span(def_id) {
+                            self.tcx
+                                .dcx()
+                                .struct_span_err(
+                                    self.tcx.def_span(item_id.owner_id),
+                                    "`impl Trait` can only capture lifetimes bound \
+                                    at the fn or impl level",
+                                )
+                                .with_span_label(
+                                    self.tcx.def_span(item_id.owner_id),
+                                    "`impl Trait` implicitly captures all lifetimes in scope",
+                                )
+                        } else {
+                            struct_span_code_err!(
+                                self.tcx.dcx(),
+                                lifetime.ident.span,
+                                E0657,
+                                "`impl Trait` can only capture lifetimes bound at the fn or impl level"
+                            )
+                        };
+                        diag.with_code(E0657)
+                            .with_span_note(self.tcx.def_span(def_id), "lifetime declared here")
+                            .emit();
                         self.uninsert_lifetime_on_error(lifetime, def.unwrap());
                     }
                     if let hir::Node::Item(hir::Item {
                         kind: hir::ItemKind::OpaqueTy { .. }, ..
                     }) = self.tcx.hir_node(parent_id)
                     {
-                        self.tcx.dcx().struct_span_err(
-                            lifetime.ident.span,
-                            "higher kinded lifetime bounds on nested opaque types are not supported yet",
-                        )
-                        .with_span_note(self.tcx.def_span(def_id), "lifetime declared here")
-                        .emit();
+                        let diag = if lifetime.ident.span == self.tcx.def_span(def_id) {
+                            // If the lifetime span is the same as the lifetime's declaration,
+                            // then it's likely we've implicitly captured the lifetime. Give
+                            // a better span and also note that it's implicitly captured.
+                            self.tcx
+                                .dcx()
+                                .struct_span_err(
+                                    self.tcx.def_span(item_id.owner_id),
+                                    "`impl Trait` captures higher-ranked lifetime, \
+                                    which is not supported yet",
+                                )
+                                .with_span_label(
+                                    self.tcx.def_span(item_id.owner_id),
+                                    "`impl Trait` implicitly captures all lifetimes in scope",
+                                )
+                        } else {
+                            self.tcx.dcx().struct_span_err(
+                                lifetime.ident.span,
+                                "higher kinded lifetime bounds on nested opaque types are not supported yet",
+                            )
+                        };
+                        diag.with_code(E0657)
+                            .with_span_note(self.tcx.def_span(def_id), "lifetime declared here")
+                            .emit();
                         self.uninsert_lifetime_on_error(lifetime, def.unwrap());
                     }
                 }

diff --git a/tests/ui/error-codes/E0657.stderr b/tests/ui/error-codes/E0657.stderr
@@ -3,12 +3,24 @@ error[E0657]: `impl Trait` can only capture lifetimes bound at the fn or impl le
    |
 LL |     -> Box<for<'a> Id<impl Lt<'a>>>
    |                               ^^
+   |
+note: lifetime declared here
+  --> $DIR/E0657.rs:10:16
+   |
+LL |     -> Box<for<'a> Id<impl Lt<'a>>>
+   |                ^^
 
 error[E0657]: `impl Trait` can only capture lifetimes bound at the fn or impl level
   --> $DIR/E0657.rs:19:35
    |
 LL |         -> Box<for<'a> Id<impl Lt<'a>>>
    |                                   ^^
+   |
+note: lifetime declared here
+  --> $DIR/E0657.rs:19:20
+   |
+LL |         -> Box<for<'a> Id<impl Lt<'a>>>
+   |                    ^^
 
 error: aborting due to 2 previous errors
 

diff --git a/tests/ui/impl-trait/impl-fn-hrtb-bounds.stderr b/tests/ui/impl-trait/impl-fn-hrtb-bounds.stderr
@@ -10,7 +10,7 @@ help: consider using the `'static` lifetime, but this is uncommon unless you're
 LL | fn d() -> impl Fn() -> (impl Debug + 'static) {
    |                                      ~~~~~~~
 
-error: higher kinded lifetime bounds on nested opaque types are not supported yet
+error[E0657]: higher kinded lifetime bounds on nested opaque types are not supported yet
   --> $DIR/impl-fn-hrtb-bounds.rs:4:41
    |
 LL | fn a() -> impl Fn(&u8) -> (impl Debug + '_) {
@@ -22,7 +22,7 @@ note: lifetime declared here
 LL | fn a() -> impl Fn(&u8) -> (impl Debug + '_) {
    |                   ^
 
-error: higher kinded lifetime bounds on nested opaque types are not supported yet
+error[E0657]: higher kinded lifetime bounds on nested opaque types are not supported yet
   --> $DIR/impl-fn-hrtb-bounds.rs:10:52
    |
 LL | fn b() -> impl for<'a> Fn(&'a u8) -> (impl Debug + 'a) {
@@ -34,7 +34,7 @@ note: lifetime declared here
 LL | fn b() -> impl for<'a> Fn(&'a u8) -> (impl Debug + 'a) {
    |                    ^^
 
-error: higher kinded lifetime bounds on nested opaque types are not supported yet
+error[E0657]: higher kinded lifetime bounds on nested opaque types are not supported yet
   --> $DIR/impl-fn-hrtb-bounds.rs:16:52
    |
 LL | fn c() -> impl for<'a> Fn(&'a u8) -> (impl Debug + '_) {
@@ -75,4 +75,5 @@ LL |     |x| x
 
 error: aborting due to 7 previous errors
 
-For more information about this error, try `rustc --explain E0106`.
+Some errors have detailed explanations: E0106, E0657.
+For more information about an error, try `rustc --explain E0106`.
diff --git a/tests/ui/impl-trait/impl-fn-parsing-ambiguities.stderr b/tests/ui/impl-trait/impl-fn-parsing-ambiguities.stderr
@@ -10,7 +10,7 @@ error: ambiguous `+` in a type
 LL | fn b() -> impl Fn() -> impl Debug + Send {
    |                        ^^^^^^^^^^^^^^^^^ help: use parentheses to disambiguate: `(impl Debug + Send)`
 
-error: higher kinded lifetime bounds on nested opaque types are not supported yet
+error[E0657]: higher kinded lifetime bounds on nested opaque types are not supported yet
   --> $DIR/impl-fn-parsing-ambiguities.rs:4:40
    |
 LL | fn a() -> impl Fn(&u8) -> impl Debug + '_ {
@@ -33,3 +33,4 @@ LL |     |x| x
 
 error: aborting due to 4 previous errors
 
+For more information about this error, try `rustc --explain E0657`.
diff --git a/tests/ui/impl-trait/implicit-capture-late.stderr b/tests/ui/impl-trait/implicit-capture-late.stderr
@@ -1,4 +1,10 @@
 error[E0657]: `impl Trait` can only capture lifetimes bound at the fn or impl level
+  --> $DIR/implicit-capture-late.rs:10:55
+   |
+LL | fn foo(x: Vec<i32>) -> Box<dyn for<'a> Deref<Target = impl ?Sized>> {
+   |                                                       ^^^^^^^^^^^ `impl Trait` implicitly captures all lifetimes in scope
+   |
+note: lifetime declared here
   --> $DIR/implicit-capture-late.rs:10:36
    |
 LL | fn foo(x: Vec<i32>) -> Box<dyn for<'a> Deref<Target = impl ?Sized>> {

diff --git a/tests/ui/impl-trait/issues/issue-54895.stderr b/tests/ui/impl-trait/issues/issue-54895.stderr
@@ -1,4 +1,4 @@
-error: higher kinded lifetime bounds on nested opaque types are not supported yet
+error[E0657]: higher kinded lifetime bounds on nested opaque types are not supported yet
   --> $DIR/issue-54895.rs:15:53
    |
 LL | fn f() -> impl for<'a> Trait<'a, Out = impl Sized + 'a> {
@@ -12,3 +12,4 @@ LL | fn f() -> impl for<'a> Trait<'a, Out = impl Sized + 'a> {
 
 error: aborting due to 1 previous error
 
+For more information about this error, try `rustc --explain E0657`.
diff --git a/tests/ui/impl-trait/issues/issue-67830.stderr b/tests/ui/impl-trait/issues/issue-67830.stderr
@@ -1,4 +1,4 @@
-error: higher kinded lifetime bounds on nested opaque types are not supported yet
+error[E0657]: higher kinded lifetime bounds on nested opaque types are not supported yet
   --> $DIR/issue-67830.rs:21:62
    |
 LL | fn test() -> impl for<'a> MyFn<&'a A, Output=impl Iterator + 'a> {
@@ -31,3 +31,4 @@ LL |     Wrap(|a| Some(a).into_iter())
 
 error: aborting due to 3 previous errors
 
+For more information about this error, try `rustc --explain E0657`.
diff --git a/tests/ui/impl-trait/issues/issue-88236-2.stderr b/tests/ui/impl-trait/issues/issue-88236-2.stderr
@@ -1,4 +1,4 @@
-error: higher kinded lifetime bounds on nested opaque types are not supported yet
+error[E0657]: higher kinded lifetime bounds on nested opaque types are not supported yet
   --> $DIR/issue-88236-2.rs:15:61
    |
 LL | fn make_impl() -> impl for<'a> Hrtb<'a, Assoc = impl Send + 'a> {}
@@ -10,7 +10,7 @@ note: lifetime declared here
 LL | fn make_impl() -> impl for<'a> Hrtb<'a, Assoc = impl Send + 'a> {}
    |                            ^^
 
-error: higher kinded lifetime bounds on nested opaque types are not supported yet
+error[E0657]: higher kinded lifetime bounds on nested opaque types are not supported yet
   --> $DIR/issue-88236-2.rs:18:80
    |
 LL | fn make_weird_impl<'b>(x: &'b ()) -> impl for<'a> Hrtb<'a, Assoc = impl Send + 'a> {
@@ -22,7 +22,7 @@ note: lifetime declared here
 LL | fn make_weird_impl<'b>(x: &'b ()) -> impl for<'a> Hrtb<'a, Assoc = impl Send + 'a> {
    |                                               ^^
 
-error: higher kinded lifetime bounds on nested opaque types are not supported yet
+error[E0657]: higher kinded lifetime bounds on nested opaque types are not supported yet
   --> $DIR/issue-88236-2.rs:25:78
    |
 LL | fn make_bad_impl<'b>(x: &'b ()) -> impl for<'a> Hrtb<'a, Assoc = impl Send + 'a> {
@@ -90,3 +90,4 @@ LL |     x
 
 error: aborting due to 8 previous errors
 
+For more information about this error, try `rustc --explain E0657`.
diff --git a/tests/ui/impl-trait/issues/issue-88236.stderr b/tests/ui/impl-trait/issues/issue-88236.stderr
@@ -1,4 +1,4 @@
-error: higher kinded lifetime bounds on nested opaque types are not supported yet
+error[E0657]: higher kinded lifetime bounds on nested opaque types are not supported yet
   --> $DIR/issue-88236.rs:15:61
    |
 LL | fn make_impl() -> impl for<'a> Hrtb<'a, Assoc = impl Send + 'a> {}
@@ -12,3 +12,4 @@ LL | fn make_impl() -> impl for<'a> Hrtb<'a, Assoc = impl Send + 'a> {}
 
 error: aborting due to 1 previous error
 
+For more information about this error, try `rustc --explain E0657`.
diff --git a/tests/ui/impl-trait/nested-rpit-hrtb.stderr b/tests/ui/impl-trait/nested-rpit-hrtb.stderr
@@ -29,7 +29,7 @@ help: consider introducing lifetime `'b` here
 LL | fn two_htrb_outlives_uses<'b>() -> impl for<'a> Bar<'a, Assoc = impl for<'b> Sized + 'b> {}
    |                          ++++
 
-error: higher kinded lifetime bounds on nested opaque types are not supported yet
+error[E0657]: higher kinded lifetime bounds on nested opaque types are not supported yet
   --> $DIR/nested-rpit-hrtb.rs:25:69
    |
 LL | fn one_hrtb_outlives() -> impl for<'a> Foo<'a, Assoc = impl Sized + 'a> {}
@@ -41,7 +41,7 @@ note: lifetime declared here
 LL | fn one_hrtb_outlives() -> impl for<'a> Foo<'a, Assoc = impl Sized + 'a> {}
    |                                    ^^
 
-error: higher kinded lifetime bounds on nested opaque types are not supported yet
+error[E0657]: higher kinded lifetime bounds on nested opaque types are not supported yet
   --> $DIR/nested-rpit-hrtb.rs:29:68
    |
 LL | fn one_hrtb_trait_param() -> impl for<'a> Foo<'a, Assoc = impl Qux<'a>> {}
@@ -53,7 +53,7 @@ note: lifetime declared here
 LL | fn one_hrtb_trait_param() -> impl for<'a> Foo<'a, Assoc = impl Qux<'a>> {}
    |                                       ^^
 
-error: higher kinded lifetime bounds on nested opaque types are not supported yet
+error[E0657]: higher kinded lifetime bounds on nested opaque types are not supported yet
   --> $DIR/nested-rpit-hrtb.rs:32:74
    |
 LL | fn one_hrtb_outlives_uses() -> impl for<'a> Bar<'a, Assoc = impl Sized + 'a> {}
@@ -65,7 +65,7 @@ note: lifetime declared here
 LL | fn one_hrtb_outlives_uses() -> impl for<'a> Bar<'a, Assoc = impl Sized + 'a> {}
    |                                         ^^
 
-error: higher kinded lifetime bounds on nested opaque types are not supported yet
+error[E0657]: higher kinded lifetime bounds on nested opaque types are not supported yet
   --> $DIR/nested-rpit-hrtb.rs:36:73
    |
 LL | fn one_hrtb_trait_param_uses() -> impl for<'a> Bar<'a, Assoc = impl Qux<'a>> {}
@@ -133,5 +133,5 @@ LL | fn two_htrb_outlives_uses() -> impl for<'a> Bar<'a, Assoc = impl for<'b> Si
 
 error: aborting due to 12 previous errors
 
-Some errors have detailed explanations: E0261, E0277.
+Some errors have detailed explanations: E0261, E0277, E0657.
 For more information about an error, try `rustc --explain E0261`.