Auto merge of #103426 - matthiaskrgr:rollup-n6dqdy8, r=matthiaskrgr

Rollup of 9 pull requests

Successful merges:

 - #103123 (Introduce `subst_iter` and `subst_iter_copied` on `EarlyBinder` )
 - #103328 (Do not suggest trivially false const predicates)
 - #103354 (Escape string literals when fixing overlong char literal)
 - #103355 (Handle return-position `impl Trait` in traits properly in `register_hidden_type`)
 - #103368 (Delay ambiguity span bug in normalize query iff not rustdoc)
 - #103388 (rustdoc: remove unused CSS class `.result-description`)
 - #103399 (Change `unknown_lint` applicability to `MaybeIncorrect`)
 - #103401 (Use functions for headings rustdoc GUI test)
 - #103412 (Fix typo in docs of `String::leak`.)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

32 files changed, 338 insertions, 192 deletions

diff --git a/src/librustdoc/html/static/css/rustdoc.css b/src/librustdoc/html/static/css/rustdoc.css
index 9785e1f54c1..324f5ffb4a9 100644
--- a/src/librustdoc/html/static/css/rustdoc.css
+++ b/src/librustdoc/html/static/css/rustdoc.css
@@ -920,7 +920,7 @@ so that we can apply CSS-filters to change the arrow color in themes */
 	flex-flow: row wrap;
 }
 
-.search-results .result-name, .search-results div.desc, .search-results .result-description {
+.search-results .result-name, .search-results div.desc {
 	width: 50%;
 }
 .search-results .result-name {
@@ -1899,10 +1899,10 @@ in storage.js
 		border-bottom: 1px solid #aaa9;
 		padding: 5px 0px;
 	}
-	.search-results .result-name, .search-results div.desc, .search-results .result-description {
+	.search-results .result-name, .search-results div.desc {
 		width: 100%;
 	}
-	.search-results div.desc, .search-results .result-description, .item-right {
+	.search-results div.desc, .item-right {
 		padding-left: 2em;
 	}
 
diff --git a/src/test/rustdoc-gui/headings.goml b/src/test/rustdoc-gui/headings.goml
index 9a77d8bbd15..85e17ca9551 100644
--- a/src/test/rustdoc-gui/headings.goml
+++ b/src/test/rustdoc-gui/headings.goml
@@ -150,109 +150,85 @@ assert-css: ("h2#top-doc-prose-title", {"border-bottom-width": "1px"})
 assert-css: ("h3#top-doc-prose-sub-heading", {"font-size": "20px"})
 assert-css: ("h3#top-doc-prose-sub-heading", {"border-bottom-width": "1px"})
 
-// Checking colors now.
+// Needed to check colors
 show-text: true
-local-storage: {"rustdoc-theme": "light", "rustdoc-use-system-theme": "false"}
 goto: "file://" + |DOC_PATH| + "/test_docs/struct.HeavilyDocumentedStruct.html"
-assert-css: (
-    ".top-doc .docblock h2",
-    {"color": "rgb(0, 0, 0)", "border-bottom": "1px solid rgb(221, 221, 221)"},
-)
-assert-css: (
-    ".top-doc .docblock h3",
-    {"color": "rgb(0, 0, 0)", "border-bottom": "1px solid rgb(221, 221, 221)"},
-)
-assert-css: (
-    ".top-doc .docblock h4",
-    {"color": "rgb(0, 0, 0)", "border-bottom": "1px solid rgb(221, 221, 221)"},
-)
-assert-css: (
-    ".top-doc .docblock h5",
-    {"color": "rgb(0, 0, 0)", "border-bottom-width": "0px"},
-)
-assert-css: (
-    "#implementations-list .docblock h4",
-    {"color": "rgb(0, 0, 0)", "border-bottom-width": "0px"},
-)
-assert-css: (
-    "#implementations-list .docblock h5",
-    {"color": "rgb(0, 0, 0)", "border-bottom-width": "0px"},
-)
-assert-css: (
-    "#implementations-list .docblock h6",
-    {"color": "rgb(0, 0, 0)", "border-bottom-width": "0px"},
-)
 
-local-storage: {"rustdoc-theme": "dark"}
-reload:
-assert-css: (
-    ".top-doc .docblock h2",
-    {"color": "rgb(221, 221, 221)", "border-bottom": "1px solid rgb(210, 210, 210)"},
-)
-assert-css: (
-    ".top-doc .docblock h3",
-    {"color": "rgb(221, 221, 221)", "border-bottom": "1px solid rgb(210, 210, 210)"},
-)
-assert-css: (
-    ".top-doc .docblock h4",
-    {"color": "rgb(221, 221, 221)", "border-bottom": "1px solid rgb(210, 210, 210)"},
-)
-assert-css: (
-    ".top-doc .docblock h5",
-    {"color": "rgb(221, 221, 221)", "border-bottom-width": "0px"},
-)
-assert-css: (
-    "#implementations-list .docblock h4",
-    {"color": "rgb(221, 221, 221)", "border-bottom-width": "0px"},
-)
-assert-css: (
-    "#implementations-list .docblock h5",
-    {"color": "rgb(221, 221, 221)", "border-bottom-width": "0px"},
-)
-assert-css: (
-    "#implementations-list .docblock h6",
-    {"color": "rgb(221, 221, 221)", "border-bottom-width": "0px"},
+define-function: (
+    "check-colors",
+    (theme, heading_color, small_heading_color, heading_border_color),
+    [
+        ("local-storage", {"rustdoc-theme": |theme|, "rustdoc-use-system-theme": "false"}),
+        ("reload"),
+        ("assert-css", (
+            ".top-doc .docblock h2",
+            {"color": |heading_color|, "border-bottom": "1px solid " + |heading_border_color|},
+        )),
+        ("assert-css", (
+            ".top-doc .docblock h3",
+            {"color": |heading_color|, "border-bottom": "1px solid " + |heading_border_color|},
+        )),
+        ("assert-css", (
+            ".top-doc .docblock h4",
+            {"color": |heading_color|, "border-bottom": "1px solid " + |heading_border_color|},
+        )),
+        ("assert-css", (
+            ".top-doc .docblock h5",
+            {"color": |small_heading_color|, "border-bottom-width": "0px"},
+        )),
+        ("assert-css", (
+            "#implementations-list .docblock h4",
+            {"color": |heading_color|, "border-bottom-width": "0px"},
+        )),
+        ("assert-css", (
+            "#implementations-list .docblock h5",
+            {"color": |small_heading_color|, "border-bottom-width": "0px"},
+        )),
+        ("assert-css", (
+            "#implementations-list .docblock h6",
+            {"color": |small_heading_color|, "border-bottom-width": "0px"},
+        )),
+    ],
+)
+call-function: (
+    "check-colors",
+    {
+        "theme": "ayu",
+        "heading_color": "rgb(255, 255, 255)",
+        "small_heading_color": "rgb(197, 197, 197)",
+        "heading_border_color": "rgb(92, 103, 115)",
+    },
+)
+call-function: (
+    "check-colors",
+    {
+        "theme": "dark",
+        "heading_color": "rgb(221, 221, 221)",
+        "small_heading_color": "rgb(221, 221, 221)",
+        "heading_border_color": "rgb(210, 210, 210)",
+    },
+)
+call-function: (
+    "check-colors",
+    {
+        "theme": "light",
+        "heading_color": "rgb(0, 0, 0)",
+        "small_heading_color": "rgb(0, 0, 0)",
+        "heading_border_color": "rgb(221, 221, 221)",
+    },
+)
+
+define-function: (
+    "check-since-color",
+    (theme),
+    [
+        ("local-storage", {"rustdoc-theme": |theme|}),
+        ("reload"),
+        ("assert-css", (".since", {"color": "rgb(128, 128, 128)"}, ALL)),
+    ],
 )
 
-local-storage: {"rustdoc-theme": "ayu"}
-reload:
-assert-css: (
-    ".top-doc .docblock h2",
-    {"color": "rgb(255, 255, 255)", "border-bottom": "1px solid rgb(92, 103, 115)"},
-)
-assert-css: (
-    ".top-doc .docblock h2",
-    {"color": "rgb(255, 255, 255)", "border-bottom": "1px solid rgb(92, 103, 115)"},
-)
-assert-css: (
-    ".top-doc .docblock h4",
-    {"color": "rgb(255, 255, 255)", "border-bottom": "1px solid rgb(92, 103, 115)"},
-)
-assert-css: (
-    ".top-doc .docblock h5",
-    {"color": "rgb(197, 197, 197)", "border-bottom-width": "0px"},
-)
-assert-css: (
-    "#implementations-list .docblock h4",
-    {"color": "rgb(255, 255, 255)", "border-bottom-width": "0px"},
-)
-assert-css: (
-    "#implementations-list .docblock h5",
-    {"color": "rgb(197, 197, 197)", "border-bottom-width": "0px"},
-)
-assert-css: (
-    "#implementations-list .docblock h6",
-    {"color": "rgb(197, 197, 197)", "border-bottom-width": "0px"},
-)
-
-local-storage: {"rustdoc-theme": "light"}
 goto: "file://" + |DOC_PATH| + "/staged_api/struct.Foo.html"
-assert-css: (".since", {"color": "rgb(128, 128, 128)"}, ALL)
-
-local-storage: {"rustdoc-theme": "dark"}
-reload:
-assert-css: (".since", {"color": "rgb(128, 128, 128)"}, ALL)
-
-local-storage: {"rustdoc-theme": "ayu"}
-reload:
-assert-css: (".since", {"color": "rgb(128, 128, 128)"}, ALL)
+call-function: ("check-since-color", ("ayu"))
+call-function: ("check-since-color", ("dark"))
+call-function: ("check-since-color", ("light"))
diff --git a/src/test/rustdoc/not-wf-ambiguous-normalization.rs b/src/test/rustdoc/not-wf-ambiguous-normalization.rs
new file mode 100644
index 00000000000..1e9f925f845
--- /dev/null
+++ b/src/test/rustdoc/not-wf-ambiguous-normalization.rs
@@ -0,0 +1,24 @@
+// compile-flags: -Znormalize-docs
+
+#![feature(type_alias_impl_trait)]
+
+trait Allocator {
+    type Buffer;
+}
+
+struct DefaultAllocator;
+
+// This unconstrained impl parameter causes the normalization of
+// `<DefaultAllocator as Allocator>::Buffer` to be ambiguous,
+// which caused an ICE with `-Znormalize-docs`.
+impl<T> Allocator for DefaultAllocator {
+    type Buffer = ();
+}
+
+type A = impl Fn(<DefaultAllocator as Allocator>::Buffer);
+
+fn foo() -> A {
+    |_| ()
+}
+
+fn main() {}
diff --git a/src/test/ui/consts/const-eval/const_raw_ptr_ops.stderr b/src/test/ui/consts/const-eval/const_raw_ptr_ops.stderr
index 168fa0ad0f0..12244450e7f 100644
--- a/src/test/ui/consts/const-eval/const_raw_ptr_ops.stderr
+++ b/src/test/ui/consts/const-eval/const_raw_ptr_ops.stderr
@@ -10,16 +10,6 @@ note: the trait `PartialEq<_>` is implemented for `*const i32`, but that impleme
    |
 LL | const X: bool = unsafe { &1 as *const i32 == &2 as *const i32 };
    |                                           ^^
-   = help: the following other types implement trait `PartialEq<Rhs>`:
-             f32
-             f64
-             i128
-             i16
-             i32
-             i64
-             i8
-             isize
-           and 6 others
 
 error[E0277]: can't compare `*const i32` with `_` in const contexts
   --> $DIR/const_raw_ptr_ops.rs:6:44
@@ -33,16 +23,6 @@ note: the trait `PartialEq<_>` is implemented for `*const i32`, but that impleme
    |
 LL | const X2: bool = unsafe { 42 as *const i32 == 43 as *const i32 };
    |                                            ^^
-   = help: the following other types implement trait `PartialEq<Rhs>`:
-             f32
-             f64
-             i128
-             i16
-             i32
-             i64
-             i8
-             isize
-           and 6 others
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/consts/issue-25826.stderr b/src/test/ui/consts/issue-25826.stderr
index b80befa26f6..905c5ee6eb4 100644
--- a/src/test/ui/consts/issue-25826.stderr
+++ b/src/test/ui/consts/issue-25826.stderr
@@ -10,10 +10,6 @@ note: the trait `PartialOrd` is implemented for `*const ()`, but that implementa
    |
 LL |     const A: bool = unsafe { id::<u8> as *const () < id::<u16> as *const () };
    |                                                    ^
-help: consider introducing a `where` clause, but there might be an alternative better way to express this requirement
-   |
-LL | fn main() where *const (): ~const PartialOrd {
-   |           ++++++++++++++++++++++++++++++++++
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/consts/issue-94675.stderr b/src/test/ui/consts/issue-94675.stderr
index 7ae293ffbf8..f4683f7f536 100644
--- a/src/test/ui/consts/issue-94675.stderr
+++ b/src/test/ui/consts/issue-94675.stderr
@@ -23,10 +23,6 @@ note: the trait `IndexMut<usize>` is implemented for `Vec<usize>`, but that impl
    |
 LL |         self.bar[0] = baz.len();
    |         ^^^^^^^^^^^
-help: consider introducing a `where` clause, but there might be an alternative better way to express this requirement
-   |
-LL | impl<'a> Foo<'a> where Vec<usize>: ~const IndexMut<usize> {
-   |                  ++++++++++++++++++++++++++++++++++++++++
 
 error: aborting due to 2 previous errors
 
diff --git a/src/test/ui/impl-trait/in-trait/default-body-type-err-2.rs b/src/test/ui/impl-trait/in-trait/default-body-type-err-2.rs
new file mode 100644
index 00000000000..45ae2b8ad3a
--- /dev/null
+++ b/src/test/ui/impl-trait/in-trait/default-body-type-err-2.rs
@@ -0,0 +1,13 @@
+// edition:2021
+
+#![allow(incomplete_features)]
+#![feature(async_fn_in_trait)]
+
+pub trait Foo {
+    async fn woopsie_async(&self) -> String {
+        42
+        //~^ ERROR mismatched types
+    }
+}
+
+fn main() {}
diff --git a/src/test/ui/impl-trait/in-trait/default-body-type-err-2.stderr b/src/test/ui/impl-trait/in-trait/default-body-type-err-2.stderr
new file mode 100644
index 00000000000..142b1bff1a4
--- /dev/null
+++ b/src/test/ui/impl-trait/in-trait/default-body-type-err-2.stderr
@@ -0,0 +1,11 @@
+error[E0308]: mismatched types
+  --> $DIR/default-body-type-err-2.rs:8:9
+   |
+LL |         42
+   |         ^^- help: try using a conversion method: `.to_string()`
+   |         |
+   |         expected struct `String`, found integer
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/src/test/ui/impl-trait/in-trait/default-body-type-err.rs b/src/test/ui/impl-trait/in-trait/default-body-type-err.rs
new file mode 100644
index 00000000000..ac9baf91cae
--- /dev/null
+++ b/src/test/ui/impl-trait/in-trait/default-body-type-err.rs
@@ -0,0 +1,13 @@
+#![allow(incomplete_features)]
+#![feature(return_position_impl_trait_in_trait)]
+
+use std::ops::Deref;
+
+pub trait Foo {
+    fn lol(&self) -> impl Deref<Target = String> {
+        //~^ type mismatch resolving `<&i32 as Deref>::Target == String`
+        &1i32
+    }
+}
+
+fn main() {}
diff --git a/src/test/ui/impl-trait/in-trait/default-body-type-err.stderr b/src/test/ui/impl-trait/in-trait/default-body-type-err.stderr
new file mode 100644
index 00000000000..461247a3e3f
--- /dev/null
+++ b/src/test/ui/impl-trait/in-trait/default-body-type-err.stderr
@@ -0,0 +1,12 @@
+error[E0271]: type mismatch resolving `<&i32 as Deref>::Target == String`
+  --> $DIR/default-body-type-err.rs:7:22
+   |
+LL |     fn lol(&self) -> impl Deref<Target = String> {
+   |                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `i32`, found struct `String`
+LL |
+LL |         &1i32
+   |         ----- return type was inferred to be `&i32` here
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0271`.
diff --git a/src/test/ui/impl-trait/in-trait/default-body-with-rpit.rs b/src/test/ui/impl-trait/in-trait/default-body-with-rpit.rs
index f0d407cd527..ad3cc7c2524 100644
--- a/src/test/ui/impl-trait/in-trait/default-body-with-rpit.rs
+++ b/src/test/ui/impl-trait/in-trait/default-body-with-rpit.rs
@@ -1,4 +1,4 @@
-// known-bug: #102688
+// check-pass
 // edition:2021
 
 #![feature(async_fn_in_trait, return_position_impl_trait_in_trait)]
diff --git a/src/test/ui/impl-trait/in-trait/default-body-with-rpit.stderr b/src/test/ui/impl-trait/in-trait/default-body-with-rpit.stderr
deleted file mode 100644
index 4529d301f9e..00000000000
--- a/src/test/ui/impl-trait/in-trait/default-body-with-rpit.stderr
+++ /dev/null
@@ -1,12 +0,0 @@
-error[E0720]: cannot resolve opaque type
-  --> $DIR/default-body-with-rpit.rs:10:28
-   |
-LL |     async fn baz(&self) -> impl Debug {
-   |                            ^^^^^^^^^^ cannot resolve opaque type
-   |
-   = note: these returned values have a concrete "never" type
-   = help: this error will resolve once the item's body returns a concrete type
-
-error: aborting due to previous error
-
-For more information about this error, try `rustc --explain E0720`.
diff --git a/src/test/ui/impl-trait/issue-103181-1.rs b/src/test/ui/impl-trait/issue-103181-1.rs
new file mode 100644
index 00000000000..197aedf9d98
--- /dev/null
+++ b/src/test/ui/impl-trait/issue-103181-1.rs
@@ -0,0 +1,85 @@
+// edition:2021
+
+mod hyper {
+    use std::{fmt::Debug, future::Future, marker::PhantomData, pin::Pin, task::Poll};
+
+    pub trait HttpBody {
+        type Error;
+    }
+    impl HttpBody for () {
+        //~^ ERROR not all trait items implemented, missing: `Error`
+        // don't implement `Error` here for the ICE
+    }
+
+    pub struct Server<I, S>(I, S);
+
+    pub fn serve<I, S>(_: S) -> Server<I, S> {
+        todo!()
+    }
+
+    impl<S, B> Future for Server<(), S>
+    where
+        S: MakeServiceRef<(), (), ResBody = B>,
+        B: HttpBody,
+        B::Error: Debug,
+    {
+        type Output = ();
+
+        fn poll(self: Pin<&mut Self>, _: &mut std::task::Context<'_>) -> Poll<Self::Output> {
+            todo!()
+        }
+    }
+
+    pub trait MakeServiceRef<Target, ReqBody> {
+        type ResBody;
+    }
+
+    impl<T, S> MakeServiceRef<(), ()> for T
+    where
+        T: for<'a> Service<&'a (), Response = S>,
+        S: Service<()>,
+    {
+        type ResBody = ();
+    }
+
+    pub struct MakeServiceFn<F>(pub F);
+    pub struct ServiceFn<F, R>(pub PhantomData<(F, R)>);
+
+    pub trait Service<Request> {
+        type Response;
+    }
+
+    impl<'t, F, Ret, Target, Svc> Service<&'t Target> for MakeServiceFn<F>
+    where
+        F: Fn() -> Ret,
+        Ret: Future<Output = Result<Svc, ()>>,
+    {
+        type Response = Svc;
+    }
+
+    impl<F, ReqBody, Ret, ResBody, E> Service<ReqBody> for ServiceFn<F, ReqBody>
+    where
+        F: Fn() -> Ret,
+        Ret: Future<Output = Result<ResBody, E>>,
+    {
+        type Response = ResBody;
+    }
+}
+
+async fn smarvice() -> Result<(), ()> {
+    Ok(())
+}
+
+fn service_fn<F, R, S>(f: F) -> hyper::ServiceFn<F, R>
+where
+    F: Fn() -> S,
+{
+    hyper::ServiceFn(std::marker::PhantomData)
+}
+
+async fn iceice() {
+    let service = hyper::MakeServiceFn(|| async { Ok::<_, ()>(service_fn(|| smarvice())) });
+    hyper::serve::<(), _>(service).await;
+}
+
+fn main() {}
diff --git a/src/test/ui/impl-trait/issue-103181-1.stderr b/src/test/ui/impl-trait/issue-103181-1.stderr
new file mode 100644
index 00000000000..cd026607d52
--- /dev/null
+++ b/src/test/ui/impl-trait/issue-103181-1.stderr
@@ -0,0 +1,12 @@
+error[E0046]: not all trait items implemented, missing: `Error`
+  --> $DIR/issue-103181-1.rs:9:5
+   |
+LL |         type Error;
+   |         ---------- `Error` from trait
+LL |     }
+LL |     impl HttpBody for () {
+   |     ^^^^^^^^^^^^^^^^^^^^ missing `Error` in implementation
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0046`.
diff --git a/src/test/ui/impl-trait/issue-103181-2.rs b/src/test/ui/impl-trait/issue-103181-2.rs
new file mode 100644
index 00000000000..b43ac45075e
--- /dev/null
+++ b/src/test/ui/impl-trait/issue-103181-2.rs
@@ -0,0 +1,29 @@
+// edition:2021
+
+trait SendFuture: Send {
+    type Output;
+}
+
+impl<Fut: Send> SendFuture for Fut {
+    type Output = ();
+}
+
+async fn broken_fut() {
+    ident_error;
+    //~^ ERROR cannot find value `ident_error` in this scope
+}
+
+// triggers normalization of `<Fut as SendFuture>::Output`,
+// which requires `Fut: Send`.
+fn normalize<Fut: SendFuture>(_: Fut, _: Fut::Output) {}
+
+async fn iceice<A, B>()
+// <- async fn is necessary
+where
+    A: Send,
+    B: Send, // <- a second bound
+{
+    normalize(broken_fut(), ());
+}
+
+fn main() {}
diff --git a/src/test/ui/impl-trait/issue-103181-2.stderr b/src/test/ui/impl-trait/issue-103181-2.stderr
new file mode 100644
index 00000000000..5eb2dd9184b
--- /dev/null
+++ b/src/test/ui/impl-trait/issue-103181-2.stderr
@@ -0,0 +1,9 @@
+error[E0425]: cannot find value `ident_error` in this scope
+  --> $DIR/issue-103181-2.rs:12:5
+   |
+LL |     ident_error;
+   |     ^^^^^^^^^^^ not found in this scope
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0425`.
diff --git a/src/test/ui/inference/char-as-str-single.fixed b/src/test/ui/inference/char-as-str-single.fixed
index e401492a830..bab1854dc51 100644
--- a/src/test/ui/inference/char-as-str-single.fixed
+++ b/src/test/ui/inference/char-as-str-single.fixed
@@ -8,4 +8,5 @@
 fn main() {
     let _: char = 'a'; //~ ERROR mismatched types
     let _: char = '人'; //~ ERROR mismatched types
+    let _: char = '\''; //~ ERROR mismatched types
 }
diff --git a/src/test/ui/inference/char-as-str-single.rs b/src/test/ui/inference/char-as-str-single.rs
index 4f23cea5354..736920643b2 100644
--- a/src/test/ui/inference/char-as-str-single.rs
+++ b/src/test/ui/inference/char-as-str-single.rs
@@ -8,4 +8,5 @@
 fn main() {
     let _: char = "a"; //~ ERROR mismatched types
     let _: char = "人"; //~ ERROR mismatched types
+    let _: char = "'"; //~ ERROR mismatched types
 }
diff --git a/src/test/ui/inference/char-as-str-single.stderr b/src/test/ui/inference/char-as-str-single.stderr
index 29075c15414..3375ec6ac32 100644
--- a/src/test/ui/inference/char-as-str-single.stderr
+++ b/src/test/ui/inference/char-as-str-single.stderr
@@ -24,6 +24,19 @@ help: if you meant to write a `char` literal, use single quotes
 LL |     let _: char = '人';
    |                   ~~~~
 
-error: aborting due to 2 previous errors
+error[E0308]: mismatched types
+  --> $DIR/char-as-str-single.rs:11:19
+   |
+LL |     let _: char = "'";
+   |            ----   ^^^ expected `char`, found `&str`
+   |            |
+   |            expected due to this
+   |
+help: if you meant to write a `char` literal, use single quotes
+   |
+LL |     let _: char = '\'';
+   |                   ~~~~
+
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0308`.
diff --git a/src/test/ui/inference/str-as-char.fixed b/src/test/ui/inference/str-as-char.fixed
index 09f3dec5a17..6aea809cbdb 100644
--- a/src/test/ui/inference/str-as-char.fixed
+++ b/src/test/ui/inference/str-as-char.fixed
@@ -4,5 +4,7 @@
 // run-rustfix
 
 fn main() {
-    let _: &str = "a"; //~ ERROR mismatched types
+    let _: &str = "a";   //~ ERROR mismatched types
+    let _: &str = "\"\"\""; //~ ERROR character literal may only contain one codepoint
+    let _: &str = "\"\"\""; //~ ERROR character literal may only contain one codepoint
 }
diff --git a/src/test/ui/inference/str-as-char.rs b/src/test/ui/inference/str-as-char.rs
index 7092a612442..eaa8d788c34 100644
--- a/src/test/ui/inference/str-as-char.rs
+++ b/src/test/ui/inference/str-as-char.rs
@@ -4,5 +4,7 @@
 // run-rustfix
 
 fn main() {
-    let _: &str = 'a'; //~ ERROR mismatched types
+    let _: &str = 'a';   //~ ERROR mismatched types
+    let _: &str = '"""'; //~ ERROR character literal may only contain one codepoint
+    let _: &str = '\"\"\"'; //~ ERROR character literal may only contain one codepoint
 }
diff --git a/src/test/ui/inference/str-as-char.stderr b/src/test/ui/inference/str-as-char.stderr
index ebbe7c80f77..2c84dac8e0c 100644
--- a/src/test/ui/inference/str-as-char.stderr
+++ b/src/test/ui/inference/str-as-char.stderr
@@ -1,3 +1,25 @@
+error: character literal may only contain one codepoint
+  --> $DIR/str-as-char.rs:8:19
+   |
+LL |     let _: &str = '"""';
+   |                   ^^^^^
+   |
+help: if you meant to write a `str` literal, use double quotes
+   |
+LL |     let _: &str = "\"\"\"";
+   |                   ~~~~~~~~
+
+error: character literal may only contain one codepoint
+  --> $DIR/str-as-char.rs:9:19
+   |
+LL |     let _: &str = '\"\"\"';
+   |                   ^^^^^^^^
+   |
+help: if you meant to write a `str` literal, use double quotes
+   |
+LL |     let _: &str = "\"\"\"";
+   |                   ~~~~~~~~
+
 error[E0308]: mismatched types
   --> $DIR/str-as-char.rs:7:19
    |
@@ -11,6 +33,6 @@ help: if you meant to write a `str` literal, use double quotes
 LL |     let _: &str = "a";
    |                   ~~~
 
-error: aborting due to previous error
+error: aborting due to 3 previous errors
 
 For more information about this error, try `rustc --explain E0308`.
diff --git a/src/test/ui/rfc-2632-const-trait-impl/assoc-type.stderr b/src/test/ui/rfc-2632-const-trait-impl/assoc-type.stderr
index ce2425010ad..89177b0f1ac 100644
--- a/src/test/ui/rfc-2632-const-trait-impl/assoc-type.stderr
+++ b/src/test/ui/rfc-2632-const-trait-impl/assoc-type.stderr
@@ -15,10 +15,6 @@ note: required by a bound in `Foo::Bar`
    |
 LL |     type Bar: ~const std::ops::Add;
    |               ^^^^^^^^^^^^^^^^^^^^ required by this bound in `Foo::Bar`
-help: consider introducing a `where` clause, but there might be an alternative better way to express this requirement
-   |
-LL | impl const Foo for NonConstAdd where NonConstAdd: ~const Add {
-   |                                +++++++++++++++++++++++++++++
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/rfc-2632-const-trait-impl/call-const-trait-method-fail.stderr b/src/test/ui/rfc-2632-const-trait-impl/call-const-trait-method-fail.stderr
index d9ad8043153..7350909ba8e 100644
--- a/src/test/ui/rfc-2632-const-trait-impl/call-const-trait-method-fail.stderr
+++ b/src/test/ui/rfc-2632-const-trait-impl/call-const-trait-method-fail.stderr
@@ -9,10 +9,6 @@ note: the trait `Plus` is implemented for `u32`, but that implementation is not
    |
 LL |     a.plus(b)
    |       ^^^^
-help: consider introducing a `where` clause, but there might be an alternative better way to express this requirement
-   |
-LL | pub const fn add_u32(a: u32, b: u32) -> u32 where u32: ~const Plus {
-   |                                             ++++++++++++++++++++++
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/rfc-2632-const-trait-impl/call-generic-method-fail.stderr b/src/test/ui/rfc-2632-const-trait-impl/call-generic-method-fail.stderr
index 83d395dda19..31e6dbdab22 100644
--- a/src/test/ui/rfc-2632-const-trait-impl/call-generic-method-fail.stderr
+++ b/src/test/ui/rfc-2632-const-trait-impl/call-generic-method-fail.stderr
@@ -9,7 +9,6 @@ note: the trait `PartialEq<_>` is implemented for `T`, but that implementation i
    |
 LL |     *t == *t
    |        ^^
-   = help: the trait `PartialEq<&B>` is implemented for `&A`
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/rfc-2632-const-trait-impl/const-default-method-bodies.stderr b/src/test/ui/rfc-2632-const-trait-impl/const-default-method-bodies.stderr
index fddc8d37f2f..c64930db9be 100644
--- a/src/test/ui/rfc-2632-const-trait-impl/const-default-method-bodies.stderr
+++ b/src/test/ui/rfc-2632-const-trait-impl/const-default-method-bodies.stderr
@@ -11,10 +11,6 @@ note: the trait `ConstDefaultFn` is implemented for `NonConstImpl`, but that imp
    |
 LL |     NonConstImpl.a();
    |     ^^^^^^^^^^^^
-help: consider introducing a `where` clause, but there might be an alternative better way to express this requirement
-   |
-LL | const fn test() where NonConstImpl: ~const ConstDefaultFn {
-   |                 +++++++++++++++++++++++++++++++++++++++++
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/rfc-2632-const-trait-impl/cross-crate.gatednc.stderr b/src/test/ui/rfc-2632-const-trait-impl/cross-crate.gatednc.stderr
index d4fa44b4bfc..925ae53e324 100644
--- a/src/test/ui/rfc-2632-const-trait-impl/cross-crate.gatednc.stderr
+++ b/src/test/ui/rfc-2632-const-trait-impl/cross-crate.gatednc.stderr
@@ -11,10 +11,6 @@ note: the trait `cross_crate::MyTrait` is implemented for `cross_crate::NonConst
    |
 LL |     NonConst.func();
    |     ^^^^^^^^
-help: consider introducing a `where` clause, but there might be an alternative better way to express this requirement
-   |
-LL | const fn const_context() where cross_crate::NonConst: ~const cross_crate::MyTrait {
-   |                          ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/rfc-2632-const-trait-impl/cross-crate.stocknc.stderr b/src/test/ui/rfc-2632-const-trait-impl/cross-crate.stocknc.stderr
index 71ecd9b0694..11db0c2b8f2 100644
--- a/src/test/ui/rfc-2632-const-trait-impl/cross-crate.stocknc.stderr
+++ b/src/test/ui/rfc-2632-const-trait-impl/cross-crate.stocknc.stderr
@@ -11,10 +11,6 @@ note: the trait `cross_crate::MyTrait` is implemented for `cross_crate::NonConst
    |
 LL |     NonConst.func();
    |     ^^^^^^^^
-help: consider introducing a `where` clause, but there might be an alternative better way to express this requirement
-   |
-LL | const fn const_context() where cross_crate::NonConst: ~const cross_crate::MyTrait {
-   |                          ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/rfc-2632-const-trait-impl/default-method-body-is-const-body-checking.stderr b/src/test/ui/rfc-2632-const-trait-impl/default-method-body-is-const-body-checking.stderr
index d102956cd2e..a244ab10cab 100644
--- a/src/test/ui/rfc-2632-const-trait-impl/default-method-body-is-const-body-checking.stderr
+++ b/src/test/ui/rfc-2632-const-trait-impl/default-method-body-is-const-body-checking.stderr
@@ -14,10 +14,6 @@ note: required by a bound in `foo`
    |
 LL | const fn foo<T>() where T: ~const Tr {}
    |                            ^^^^^^^^^ required by this bound in `foo`
-help: consider introducing a `where` clause, but there might be an alternative better way to express this requirement
-   |
-LL | pub trait Foo where (): ~const Tr {
-   |               +++++++++++++++++++
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/rfc-2632-const-trait-impl/default-method-body-is-const-same-trait-ck.stderr b/src/test/ui/rfc-2632-const-trait-impl/default-method-body-is-const-same-trait-ck.stderr
index 85285ba8497..c2c16921c2e 100644
--- a/src/test/ui/rfc-2632-const-trait-impl/default-method-body-is-const-same-trait-ck.stderr
+++ b/src/test/ui/rfc-2632-const-trait-impl/default-method-body-is-const-same-trait-ck.stderr
@@ -11,10 +11,6 @@ note: the trait `Tr` is implemented for `()`, but that implementation is not `co
    |
 LL |         ().a()
    |         ^^
-help: consider introducing a `where` clause, but there might be an alternative better way to express this requirement
-   |
-LL | pub trait Tr where (): ~const Tr {
-   |              +++++++++++++++++++
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/rfc-2632-const-trait-impl/super-traits-fail.stderr b/src/test/ui/rfc-2632-const-trait-impl/super-traits-fail.stderr
index 9787792ab13..1f8f312df01 100644
--- a/src/test/ui/rfc-2632-const-trait-impl/super-traits-fail.stderr
+++ b/src/test/ui/rfc-2632-const-trait-impl/super-traits-fail.stderr
@@ -14,10 +14,6 @@ note: required by a bound in `Bar`
    |
 LL | trait Bar: ~const Foo {}
    |            ^^^^^^^^^^ required by this bound in `Bar`
-help: consider introducing a `where` clause, but there might be an alternative better way to express this requirement
-   |
-LL | impl const Bar for S where S: ~const Foo {}
-   |                      +++++++++++++++++++
 
 error: aborting due to previous error
 
diff --git a/src/tools/clippy/clippy_utils/src/ty.rs b/src/tools/clippy/clippy_utils/src/ty.rs
index a15daec7c3c..3b5a9ba8356 100644
--- a/src/tools/clippy/clippy_utils/src/ty.rs
+++ b/src/tools/clippy/clippy_utils/src/ty.rs
@@ -657,21 +657,18 @@ fn sig_for_projection<'tcx>(cx: &LateContext<'tcx>, ty: ProjectionTy<'tcx>) -> O
     let mut output = None;
     let lang_items = cx.tcx.lang_items();
 
-    for pred in cx
+    for (pred, _) in cx
         .tcx
         .bound_explicit_item_bounds(ty.item_def_id)
-        .transpose_iter()
-        .map(|x| x.map_bound(|(p, _)| p))
+        .subst_iter_copied(cx.tcx, ty.substs)
     {
-        match pred.0.kind().skip_binder() {
+        match pred.kind().skip_binder() {
             PredicateKind::Trait(p)
                 if (lang_items.fn_trait() == Some(p.def_id())
                     || lang_items.fn_mut_trait() == Some(p.def_id())
                     || lang_items.fn_once_trait() == Some(p.def_id())) =>
             {
-                let i = pred
-                    .map_bound(|pred| pred.kind().rebind(p.trait_ref.substs.type_at(1)))
-                    .subst(cx.tcx, ty.substs);
+                let i = pred.kind().rebind(p.trait_ref.substs.type_at(1));
 
                 if inputs.map_or(false, |inputs| inputs != i) {
                     // Multiple different fn trait impls. Is this even allowed?
@@ -684,10 +681,7 @@ fn sig_for_projection<'tcx>(cx: &LateContext<'tcx>, ty: ProjectionTy<'tcx>) -> O
                     // Multiple different fn trait impls. Is this even allowed?
                     return None;
                 }
-                output = Some(
-                    pred.map_bound(|pred| pred.kind().rebind(p.term.ty().unwrap()))
-                        .subst(cx.tcx, ty.substs),
-                );
+                output = pred.kind().rebind(p.term.ty()).transpose();
             },
             _ => (),
         }