Auto merge of #126049 - compiler-errors:rework-use, r=oli-obk

Rework `feature(precise_capturing)` to represent `use<...>` as a syntactical bound

Reworks `precise_capturing` for a recent lang-team consensus.

Specifically:

> The conclusion of the team is that we'll make use<..> a bound. That is, we'll support impl use<..> + Trait, impl Trait + use<..>, etc.

> For now, we will support at most one such bound in a list of bounds, and semantically we'll only support these bounds in the item bounds of RPIT-like impl Trait opaque types (i.e., in the places discussed in the RFC).

Lang decision in favor of this approach:

- https://github.com/rust-lang/rust/issues/125836#issuecomment-2151351849

Tracking:

- https://github.com/rust-lang/rust/issues/123432

1 files changed, 15 insertions, 1 deletions

diff --git a/compiler/rustc_hir_pretty/src/lib.rs b/compiler/rustc_hir_pretty/src/lib.rs
index d32d0183c4e..b21f1eadfb7 100644
--- a/compiler/rustc_hir_pretty/src/lib.rs
+++ b/compiler/rustc_hir_pretty/src/lib.rs
@@ -13,7 +13,7 @@ use rustc_ast_pretty::pprust::{Comments, PrintState};
 use rustc_hir as hir;
 use rustc_hir::{
     BindingMode, ByRef, GenericArg, GenericBound, GenericParam, GenericParamKind, HirId,
-    LifetimeParamKind, Node, PatKind, RangeEnd, Term, TraitBoundModifier,
+    LifetimeParamKind, Node, PatKind, PreciseCapturingArg, RangeEnd, Term, TraitBoundModifier,
 };
 use rustc_span::source_map::SourceMap;
 use rustc_span::symbol::{kw, Ident, Symbol};
@@ -2100,10 +2100,24 @@ impl<'a> State<'a> {
                 GenericBound::Outlives(lt) => {
                     self.print_lifetime(lt);
                 }
+                GenericBound::Use(args, _) => {
+                    self.word("use <");
+
+                    self.commasep(Inconsistent, args, |s, arg| s.print_precise_capturing_arg(*arg));
+
+                    self.word(">");
+                }
             }
         }
     }
 
+    fn print_precise_capturing_arg(&mut self, arg: PreciseCapturingArg<'_>) {
+        match arg {
+            PreciseCapturingArg::Lifetime(lt) => self.print_lifetime(lt),
+            PreciseCapturingArg::Param(arg) => self.print_ident(arg.ident),
+        }
+    }
+
     fn print_generic_params(&mut self, generic_params: &[GenericParam<'_>]) {
         if !generic_params.is_empty() {
             self.word("<");