From 83b868c82339e70484a5b25f0e2c5f8bdb4e200f Mon Sep 17 00:00:00 2001
From: Ranjit Jhala <rjhala@ucsd.edu>
Date: Tue, 10 Dec 2024 14:01:52 -0800
Subject: [PATCH] use impl fmt::Write instead of Formatter

---
 crates/flux-middle/src/lib.rs        | 4 +---
 crates/flux-middle/src/pretty.rs     | 2 +-
 crates/flux-middle/src/rty/pretty.rs | 3 +--
 3 files changed, 3 insertions(+), 6 deletions(-)

diff --git a/crates/flux-middle/src/lib.rs b/crates/flux-middle/src/lib.rs
index a7608725c4..3be918e6d6 100644
--- a/crates/flux-middle/src/lib.rs
+++ b/crates/flux-middle/src/lib.rs
@@ -1,5 +1,4 @@
 //! This crate contains common type definitions that are used by other crates.
-#![allow(internal_features)] // TODO: needed for the fmt_internals, which is needed for `nested_with_bound_vars`
 #![feature(
     associated_type_defaults,
     box_patterns,
@@ -10,8 +9,7 @@
     min_specialization,
     never_type,
     rustc_private,
-    unwrap_infallible,
-    fmt_internals
+    unwrap_infallible
 )]
 
 extern crate rustc_ast;
diff --git a/crates/flux-middle/src/pretty.rs b/crates/flux-middle/src/pretty.rs
index a6d9ffbbe3..62f813b9ed 100644
--- a/crates/flux-middle/src/pretty.rs
+++ b/crates/flux-middle/src/pretty.rs
@@ -332,7 +332,7 @@ impl<'genv, 'tcx> PrettyCx<'genv, 'tcx> {
         left: &str,
         vars: &[BoundVariableKind],
         right: &str,
-        f: &mut fmt::Formatter<'_>,
+        f: &mut impl fmt::Write,
     ) -> fmt::Result {
         define_scoped!(self, f);
         w!("{left}")?;
diff --git a/crates/flux-middle/src/rty/pretty.rs b/crates/flux-middle/src/rty/pretty.rs
index 52939d8e12..77d95b8a1c 100644
--- a/crates/flux-middle/src/rty/pretty.rs
+++ b/crates/flux-middle/src/rty/pretty.rs
@@ -726,9 +726,8 @@ pub fn nested_with_bound_vars(
     f: impl FnOnce(String) -> Result<NestedString, fmt::Error>,
 ) -> Result<NestedString, fmt::Error> {
     let mut buffer = String::new();
-    let mut formatter = fmt::Formatter::new(&mut buffer);
     if !vars.is_empty() {
-        cx.fmt_bound_vars(false, left, vars, ". ", &mut formatter)?;
+        cx.fmt_bound_vars(false, left, vars, ". ", &mut buffer)?;
     }
     f(buffer)
 }