Auto merge of rust-lang#115696 - RalfJung:closure-ty-print, r=oli-obk

adjust how closure/generator types are printed

I saw `&[closure@$DIR/issue-20862.rs:2:5]` and I thought it is a slice type, because that's usually what `&[_]` is... it took me a while to realize that this is just a confusing printer and actually there's no slice. Let's use something that cannot be mistaken for a regular type.

Author: bors

compiler/rustc_infer/src/infer/error_reporting/mod.rs

@@ -1616,7 +1616,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     //    |     expected `()`, found closure
                     //    |
                     //    = note: expected unit type `()`
-                    //                 found closure `[closure@$DIR/issue-20862.rs:2:5: 2:14 x:_]`
+                    //                 found closure `{closure@$DIR/issue-20862.rs:2:5: 2:14 x:_}`
                     //
                     // Also ignore opaque `Future`s that come from async fns.
                     if !self.ignore_span.overlaps(span)

compiler/rustc_middle/src/mir/pretty.rs

@@ -1001,11 +1001,11 @@ impl<'tcx> Debug for Rvalue<'tcx> {
                     AggregateKind::Closure(def_id, args) => ty::tls::with(|tcx| {
                         let name = if tcx.sess.opts.unstable_opts.span_free_formats {
                             let args = tcx.lift(args).unwrap();
-                            format!("[closure@{}]", tcx.def_path_str_with_args(def_id, args),)
+                            format!("{{closure@{}}}", tcx.def_path_str_with_args(def_id, args),)
                         } else {
                             let span = tcx.def_span(def_id);
                             format!(
-                                "[closure@{}]",
+                                "{{closure@{}}}",
                                 tcx.sess.source_map().span_to_diagnostic_string(span)
                             )
                         };
@@ -1029,7 +1029,7 @@ impl<'tcx> Debug for Rvalue<'tcx> {
                     }),
 
                     AggregateKind::Generator(def_id, _, _) => ty::tls::with(|tcx| {
-                        let name = format!("[generator@{:?}]", tcx.def_span(def_id));
+                        let name = format!("{{generator@{:?}}}", tcx.def_span(def_id));
                         let mut struct_fmt = fmt.debug_struct(&name);
 
                         // FIXME(project-rfc-2229#48): This should be a list of capture names/places

compiler/rustc_middle/src/ty/print/pretty.rs

@@ -795,7 +795,7 @@ pub trait PrettyPrinter<'tcx>:
             }
             ty::Str => p!("str"),
             ty::Generator(did, args, movability) => {
-                p!(write("["));
+                p!(write("{{"));
                 let generator_kind = self.tcx().generator_kind(did).unwrap();
                 let should_print_movability =
                     self.should_print_verbose() || generator_kind == hir::GeneratorKind::Gen;
@@ -836,13 +836,13 @@ pub trait PrettyPrinter<'tcx>:
                     }
                 }
 
-                p!("]")
+                p!("}}")
             }
             ty::GeneratorWitness(types) => {
                 p!(in_binder(&types));
             }
             ty::GeneratorWitnessMIR(did, args) => {
-                p!(write("["));
+                p!(write("{{"));
                 if !self.tcx().sess.verbose() {
                     p!("generator witness");
                     // FIXME(eddyb) should use `def_span`.
@@ -861,10 +861,10 @@ pub trait PrettyPrinter<'tcx>:
                     p!(print_def_path(did, args));
                 }
 
-                p!("]")
+                p!("}}")
             }
             ty::Closure(did, args) => {
-                p!(write("["));
+                p!(write("{{"));
                 if !self.should_print_verbose() {
                     p!(write("closure"));
                     // FIXME(eddyb) should use `def_span`.
@@ -904,7 +904,7 @@ pub trait PrettyPrinter<'tcx>:
                         p!(")");
                     }
                 }
-                p!("]");
+                p!("}}");
             }
             ty::Array(ty, sz) => p!("[", print(ty), "; ", print(sz), "]"),
             ty::Slice(ty) => p!("[", print(ty), "]"),
@@ -1061,7 +1061,7 @@ pub trait PrettyPrinter<'tcx>:
                     }
 
                     for (assoc_item_def_id, term) in assoc_items {
-                        // Skip printing `<[generator@] as Generator<_>>::Return` from async blocks,
+                        // Skip printing `<{generator@} as Generator<_>>::Return` from async blocks,
                         // unless we can find out what generator return type it comes from.
                         let term = if let Some(ty) = term.skip_binder().ty()
                             && let ty::Alias(ty::Projection, proj) = ty.kind()

compiler/rustc_middle/src/ty/sty.rs

@@ -2550,7 +2550,7 @@ impl<'tcx> Ty<'tcx> {
 
     /// Checks whether a type recursively contains any closure
     ///
-    /// Example: `Option<[closure@file.rs:4:20]>` returns true
+    /// Example: `Option<{closure@file.rs:4:20}>` returns true
     pub fn contains_closure(self) -> bool {
         struct ContainsClosureVisitor;
 

src/tools/clippy/tests/ui/box_default.fixed

@@ -36,7 +36,7 @@ fn main() {
     issue_10381();
 
     // `Box::<Option<_>>::default()` would be valid here, but not `Box::default()` or
-    // `Box::<Option<[closure@...]>::default()`
+    // `Box::<Option<{closure@...}>::default()`
     //
     // Would have a suggestion after https://github.com/rust-lang/rust/blob/fdd030127cc68afec44a8d3f6341525dd34e50ae/compiler/rustc_middle/src/ty/diagnostics.rs#L554-L563
     let mut unnameable = Box::new(Option::default());

src/tools/clippy/tests/ui/box_default.rs

@@ -36,7 +36,7 @@ fn main() {
     issue_10381();
 
     // `Box::<Option<_>>::default()` would be valid here, but not `Box::default()` or
-    // `Box::<Option<[closure@...]>::default()`
+    // `Box::<Option<{closure@...}>::default()`
     //
     // Would have a suggestion after https://github.com/rust-lang/rust/blob/fdd030127cc68afec44a8d3f6341525dd34e50ae/compiler/rustc_middle/src/ty/diagnostics.rs#L554-L563
     let mut unnameable = Box::new(Option::default());

src/tools/clippy/tests/ui/crashes/ice-6251.stderr

@@ -27,7 +27,7 @@ LL | fn bug<T>() -> impl Iterator<Item = [(); { |x: [u8]| x }]> {
    |                                            ^^^^^^^^^^^ expected `usize`, found closure
    |
    = note: expected type `usize`
-           found closure `[closure@$DIR/ice-6251.rs:4:44: 4:53]`
+           found closure `{closure@$DIR/ice-6251.rs:4:44: 4:53}`
 
 error: aborting due to 3 previous errors
 

src/tools/miri/tests/fail/both_borrows/newtype_pair_retagging.stack.stderr

@@ -24,7 +24,7 @@ note: inside closure
    |
 LL |             || drop(Box::from_raw(ptr)),
    |                     ^^^^^^^^^^^^^^^^^^
-note: inside `dealloc_while_running::<[closure@$DIR/newtype_pair_retagging.rs:LL:CC]>`
+note: inside `dealloc_while_running::<{closure@$DIR/newtype_pair_retagging.rs:LL:CC}>`
   --> $DIR/newtype_pair_retagging.rs:LL:CC
    |
 LL |     dealloc();

src/tools/miri/tests/fail/both_borrows/newtype_pair_retagging.tree.stderr

@@ -35,7 +35,7 @@ note: inside closure
    |
 LL |             || drop(Box::from_raw(ptr)),
    |                ^^^^^^^^^^^^^^^^^^^^^^^^
-note: inside `dealloc_while_running::<[closure@$DIR/newtype_pair_retagging.rs:LL:CC]>`
+note: inside `dealloc_while_running::<{closure@$DIR/newtype_pair_retagging.rs:LL:CC}>`
   --> $DIR/newtype_pair_retagging.rs:LL:CC
    |
 LL |     dealloc();

src/tools/miri/tests/fail/both_borrows/newtype_retagging.stack.stderr

@@ -24,7 +24,7 @@ note: inside closure
    |
 LL |             || drop(Box::from_raw(ptr)),
    |                     ^^^^^^^^^^^^^^^^^^
-note: inside `dealloc_while_running::<[closure@$DIR/newtype_retagging.rs:LL:CC]>`
+note: inside `dealloc_while_running::<{closure@$DIR/newtype_retagging.rs:LL:CC}>`
   --> $DIR/newtype_retagging.rs:LL:CC
    |
 LL |     dealloc();