diff --git a/compiler/rustc_ast/src/mut_visit.rs b/compiler/rustc_ast/src/mut_visit.rs
index 205625573a6d9..6bf23af81bf6b 100644
--- a/compiler/rustc_ast/src/mut_visit.rs
+++ b/compiler/rustc_ast/src/mut_visit.rs
@@ -1,5 +1,5 @@
 //! A `MutVisitor` represents an AST modification; it accepts an AST piece and
-//! and mutates it in place. So, for instance, macro expansion is a `MutVisitor`
+//! mutates it in place. So, for instance, macro expansion is a `MutVisitor`
 //! that walks over an AST and modifies it.
 //!
 //! Note: using a `MutVisitor` (other than the `MacroExpander` `MutVisitor`) on
diff --git a/compiler/rustc_const_eval/src/interpret/operator.rs b/compiler/rustc_const_eval/src/interpret/operator.rs
index a90582fc33820..48c90e1881a9a 100644
--- a/compiler/rustc_const_eval/src/interpret/operator.rs
+++ b/compiler/rustc_const_eval/src/interpret/operator.rs
@@ -328,9 +328,10 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
                 self.binary_int_op(bin_op, l, left.layout, r, right.layout)
             }
             _ if left.layout.ty.is_any_ptr() => {
-                // The RHS type must be the same *or an integer type* (for `Offset`).
+                // The RHS type must be a `pointer` *or an integer type* (for `Offset`).
+                // (Even when both sides are pointers, their type might differ, see issue #91636)
                 assert!(
-                    right.layout.ty == left.layout.ty || right.layout.ty.is_integral(),
+                    right.layout.ty.is_any_ptr() || right.layout.ty.is_integral(),
                     "Unexpected types for BinOp: {:?} {:?} {:?}",
                     left.layout.ty,
                     bin_op,
diff --git a/compiler/rustc_mir_transform/src/const_prop.rs b/compiler/rustc_mir_transform/src/const_prop.rs
index e897e89982c0d..84bdb8eece654 100644
--- a/compiler/rustc_mir_transform/src/const_prop.rs
+++ b/compiler/rustc_mir_transform/src/const_prop.rs
@@ -752,62 +752,44 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
         rvalue: &Rvalue<'tcx>,
         place: Place<'tcx>,
     ) -> Option<()> {
-        self.use_ecx(|this| {
-            match rvalue {
-                Rvalue::BinaryOp(op, box (left, right))
-                | Rvalue::CheckedBinaryOp(op, box (left, right)) => {
-                    let l = this.ecx.eval_operand(left, None);
-                    let r = this.ecx.eval_operand(right, None);
-
-                    let const_arg = match (l, r) {
-                        (Ok(ref x), Err(_)) | (Err(_), Ok(ref x)) => this.ecx.read_immediate(x)?,
-                        (Err(e), Err(_)) => return Err(e),
-                        (Ok(_), Ok(_)) => {
-                            this.ecx.eval_rvalue_into_place(rvalue, place)?;
-                            return Ok(());
-                        }
-                    };
-
-                    let arg_value = const_arg.to_scalar()?.to_bits(const_arg.layout.size)?;
-                    let dest = this.ecx.eval_place(place)?;
-
-                    match op {
-                        BinOp::BitAnd => {
-                            if arg_value == 0 {
-                                this.ecx.write_immediate(*const_arg, &dest)?;
-                            }
-                        }
-                        BinOp::BitOr => {
-                            if arg_value == const_arg.layout.size.truncate(u128::MAX)
-                                || (const_arg.layout.ty.is_bool() && arg_value == 1)
-                            {
-                                this.ecx.write_immediate(*const_arg, &dest)?;
-                            }
-                        }
-                        BinOp::Mul => {
-                            if const_arg.layout.ty.is_integral() && arg_value == 0 {
-                                if let Rvalue::CheckedBinaryOp(_, _) = rvalue {
-                                    let val = Immediate::ScalarPair(
-                                        const_arg.to_scalar()?.into(),
-                                        Scalar::from_bool(false).into(),
-                                    );
-                                    this.ecx.write_immediate(val, &dest)?;
-                                } else {
-                                    this.ecx.write_immediate(*const_arg, &dest)?;
-                                }
-                            }
-                        }
-                        _ => {
-                            this.ecx.eval_rvalue_into_place(rvalue, place)?;
+        self.use_ecx(|this| match rvalue {
+            Rvalue::BinaryOp(op, box (left, right))
+            | Rvalue::CheckedBinaryOp(op, box (left, right)) => {
+                let l = this.ecx.eval_operand(left, None);
+                let r = this.ecx.eval_operand(right, None);
+
+                let const_arg = match (l, r) {
+                    (Ok(ref x), Err(_)) | (Err(_), Ok(ref x)) => this.ecx.read_immediate(x)?,
+                    (Err(e), Err(_)) => return Err(e),
+                    (Ok(_), Ok(_)) => return this.ecx.eval_rvalue_into_place(rvalue, place),
+                };
+
+                let arg_value = const_arg.to_scalar()?.to_bits(const_arg.layout.size)?;
+                let dest = this.ecx.eval_place(place)?;
+
+                match op {
+                    BinOp::BitAnd if arg_value == 0 => this.ecx.write_immediate(*const_arg, &dest),
+                    BinOp::BitOr
+                        if arg_value == const_arg.layout.size.truncate(u128::MAX)
+                            || (const_arg.layout.ty.is_bool() && arg_value == 1) =>
+                    {
+                        this.ecx.write_immediate(*const_arg, &dest)
+                    }
+                    BinOp::Mul if const_arg.layout.ty.is_integral() && arg_value == 0 => {
+                        if let Rvalue::CheckedBinaryOp(_, _) = rvalue {
+                            let val = Immediate::ScalarPair(
+                                const_arg.to_scalar()?.into(),
+                                Scalar::from_bool(false).into(),
+                            );
+                            this.ecx.write_immediate(val, &dest)
+                        } else {
+                            this.ecx.write_immediate(*const_arg, &dest)
                         }
                     }
-                }
-                _ => {
-                    this.ecx.eval_rvalue_into_place(rvalue, place)?;
+                    _ => this.ecx.eval_rvalue_into_place(rvalue, place),
                 }
             }
-
-            Ok(())
+            _ => this.ecx.eval_rvalue_into_place(rvalue, place),
         })
     }
 
diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index 0f8c0e1b8cff8..c62ebb271f4b0 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -213,11 +213,11 @@ impl<'a> Parser<'a> {
                 }
             }
 
+            // Look for JS' `===` and `!==` and recover
             if (op.node == AssocOp::Equal || op.node == AssocOp::NotEqual)
                 && self.token.kind == token::Eq
                 && self.prev_token.span.hi() == self.token.span.lo()
             {
-                // Look for JS' `===` and `!==` and recover 😇
                 let sp = op.span.to(self.token.span);
                 let sugg = match op.node {
                     AssocOp::Equal => "==",
@@ -235,6 +235,38 @@ impl<'a> Parser<'a> {
                 self.bump();
             }
 
+            // Look for PHP's `<>` and recover
+            if op.node == AssocOp::Less
+                && self.token.kind == token::Gt
+                && self.prev_token.span.hi() == self.token.span.lo()
+            {
+                let sp = op.span.to(self.token.span);
+                self.struct_span_err(sp, "invalid comparison operator `<>`")
+                    .span_suggestion_short(
+                        sp,
+                        "`<>` is not a valid comparison operator, use `!=`",
+                        "!=".to_string(),
+                        Applicability::MachineApplicable,
+                    )
+                    .emit();
+                self.bump();
+            }
+
+            // Look for C++'s `<=>` and recover
+            if op.node == AssocOp::LessEqual
+                && self.token.kind == token::Gt
+                && self.prev_token.span.hi() == self.token.span.lo()
+            {
+                let sp = op.span.to(self.token.span);
+                self.struct_span_err(sp, "invalid comparison operator `<=>`")
+                    .span_label(
+                        sp,
+                        "`<=>` is not a valid comparison operator, use `std::cmp::Ordering`",
+                    )
+                    .emit();
+                self.bump();
+            }
+
             let op = op.node;
             // Special cases:
             if op == AssocOp::As {
diff --git a/compiler/rustc_resolve/src/late/diagnostics.rs b/compiler/rustc_resolve/src/late/diagnostics.rs
index feb4f82ce8ddc..3e1afdfa9a5c6 100644
--- a/compiler/rustc_resolve/src/late/diagnostics.rs
+++ b/compiler/rustc_resolve/src/late/diagnostics.rs
@@ -298,11 +298,16 @@ impl<'a: 'ast, 'ast> LateResolutionVisitor<'a, '_, 'ast> {
                             .get(0)
                             .map(|p| (p.span.shrink_to_lo(), "&self, "))
                             .unwrap_or_else(|| {
+                                // Try to look for the "(" after the function name, if possible.
+                                // This avoids placing the suggestion into the visibility specifier.
+                                let span = fn_kind
+                                    .ident()
+                                    .map_or(*span, |ident| span.with_lo(ident.span.hi()));
                                 (
                                     self.r
                                         .session
                                         .source_map()
-                                        .span_through_char(*span, '(')
+                                        .span_through_char(span, '(')
                                         .shrink_to_hi(),
                                     "&self",
                                 )
diff --git a/library/alloc/tests/slice.rs b/library/alloc/tests/slice.rs
index 13b8c059e37ae..18ea6a2141377 100644
--- a/library/alloc/tests/slice.rs
+++ b/library/alloc/tests/slice.rs
@@ -863,7 +863,7 @@ fn test_splitator_inclusive() {
     assert_eq!(xs.split_inclusive(|_| true).collect::<Vec<&[i32]>>(), splits);
 
     let xs: &[i32] = &[];
-    let splits: &[&[i32]] = &[&[]];
+    let splits: &[&[i32]] = &[];
     assert_eq!(xs.split_inclusive(|x| *x == 5).collect::<Vec<&[i32]>>(), splits);
 }
 
@@ -883,7 +883,7 @@ fn test_splitator_inclusive_reverse() {
     assert_eq!(xs.split_inclusive(|_| true).rev().collect::<Vec<_>>(), splits);
 
     let xs: &[i32] = &[];
-    let splits: &[&[i32]] = &[&[]];
+    let splits: &[&[i32]] = &[];
     assert_eq!(xs.split_inclusive(|x| *x == 5).rev().collect::<Vec<_>>(), splits);
 }
 
@@ -903,7 +903,7 @@ fn test_splitator_mut_inclusive() {
     assert_eq!(xs.split_inclusive_mut(|_| true).collect::<Vec<_>>(), splits);
 
     let xs: &mut [i32] = &mut [];
-    let splits: &[&[i32]] = &[&[]];
+    let splits: &[&[i32]] = &[];
     assert_eq!(xs.split_inclusive_mut(|x| *x == 5).collect::<Vec<_>>(), splits);
 }
 
@@ -923,7 +923,7 @@ fn test_splitator_mut_inclusive_reverse() {
     assert_eq!(xs.split_inclusive_mut(|_| true).rev().collect::<Vec<_>>(), splits);
 
     let xs: &mut [i32] = &mut [];
-    let splits: &[&[i32]] = &[&[]];
+    let splits: &[&[i32]] = &[];
     assert_eq!(xs.split_inclusive_mut(|x| *x == 5).rev().collect::<Vec<_>>(), splits);
 }
 
diff --git a/library/core/src/slice/iter.rs b/library/core/src/slice/iter.rs
index ad1d6b8b846a0..11a57558f67d7 100644
--- a/library/core/src/slice/iter.rs
+++ b/library/core/src/slice/iter.rs
@@ -481,7 +481,8 @@ where
 impl<'a, T: 'a, P: FnMut(&T) -> bool> SplitInclusive<'a, T, P> {
     #[inline]
     pub(super) fn new(slice: &'a [T], pred: P) -> Self {
-        Self { v: slice, pred, finished: false }
+        let finished = slice.is_empty();
+        Self { v: slice, pred, finished }
     }
 }
 
@@ -729,7 +730,8 @@ where
 impl<'a, T: 'a, P: FnMut(&T) -> bool> SplitInclusiveMut<'a, T, P> {
     #[inline]
     pub(super) fn new(slice: &'a mut [T], pred: P) -> Self {
-        Self { v: slice, pred, finished: false }
+        let finished = slice.is_empty();
+        Self { v: slice, pred, finished }
     }
 }
 
diff --git a/src/test/ui/binop/binary-op-on-fn-ptr-eq.rs b/src/test/ui/binop/binary-op-on-fn-ptr-eq.rs
new file mode 100644
index 0000000000000..8e20640b58d94
--- /dev/null
+++ b/src/test/ui/binop/binary-op-on-fn-ptr-eq.rs
@@ -0,0 +1,9 @@
+// run-pass
+// Tests equality between supertype and subtype of a function
+// See the issue #91636
+fn foo(_a: &str) {}
+
+fn main() {
+    let x = foo as fn(&'static str);
+    let _ = x == foo;
+}
diff --git a/src/test/ui/issues/issue-87490.rs b/src/test/ui/issues/issue-87490.rs
new file mode 100644
index 0000000000000..998f61a6bd32d
--- /dev/null
+++ b/src/test/ui/issues/issue-87490.rs
@@ -0,0 +1,10 @@
+fn main() {}
+trait StreamOnce {
+    type Position;
+}
+impl StreamOnce for &str {
+    type Position = usize;
+}
+fn follow(_: &str) -> <&str as StreamOnce>::Position {
+    String::new  //~ ERROR mismatched types
+}
diff --git a/src/test/ui/issues/issue-87490.stderr b/src/test/ui/issues/issue-87490.stderr
new file mode 100644
index 0000000000000..f359dd638ad93
--- /dev/null
+++ b/src/test/ui/issues/issue-87490.stderr
@@ -0,0 +1,14 @@
+error[E0308]: mismatched types
+  --> $DIR/issue-87490.rs:9:5
+   |
+LL | fn follow(_: &str) -> <&str as StreamOnce>::Position {
+   |                       ------------------------------ expected `usize` because of return type
+LL |     String::new
+   |     ^^^^^^^^^^^ expected `usize`, found fn item
+   |
+   = note: expected type `usize`
+           found fn item `fn() -> String {String::new}`
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.
diff --git a/src/test/ui/mir/mir_const_prop_identity.rs b/src/test/ui/mir/mir_const_prop_identity.rs
new file mode 100644
index 0000000000000..25d2202b909d9
--- /dev/null
+++ b/src/test/ui/mir/mir_const_prop_identity.rs
@@ -0,0 +1,12 @@
+// Regression test for issue #91725.
+//
+// run-pass
+// compile-flags: -Zmir-opt-level=4
+
+fn main() {
+    let a = true;
+    let _ = &a;
+    let mut b = false;
+    b |= a;
+    assert!(b);
+}
diff --git a/src/test/ui/operator-recovery/less-than-greater-than.rs b/src/test/ui/operator-recovery/less-than-greater-than.rs
new file mode 100644
index 0000000000000..2beed528ff1c1
--- /dev/null
+++ b/src/test/ui/operator-recovery/less-than-greater-than.rs
@@ -0,0 +1,4 @@
+fn main() {
+    println!("{}", 1 <> 2);
+    //~^ERROR invalid comparison operator `<>`
+}
diff --git a/src/test/ui/operator-recovery/less-than-greater-than.stderr b/src/test/ui/operator-recovery/less-than-greater-than.stderr
new file mode 100644
index 0000000000000..80c921535bd08
--- /dev/null
+++ b/src/test/ui/operator-recovery/less-than-greater-than.stderr
@@ -0,0 +1,8 @@
+error: invalid comparison operator `<>`
+  --> $DIR/less-than-greater-than.rs:2:22
+   |
+LL |     println!("{}", 1 <> 2);
+   |                      ^^ help: `<>` is not a valid comparison operator, use `!=`
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/operator-recovery/spaceship.rs b/src/test/ui/operator-recovery/spaceship.rs
new file mode 100644
index 0000000000000..a65f9389625fc
--- /dev/null
+++ b/src/test/ui/operator-recovery/spaceship.rs
@@ -0,0 +1,4 @@
+fn main() {
+    println!("{}", 1 <=> 2);
+    //~^ERROR invalid comparison operator `<=>`
+}
diff --git a/src/test/ui/operator-recovery/spaceship.stderr b/src/test/ui/operator-recovery/spaceship.stderr
new file mode 100644
index 0000000000000..ed6bd74c9b92e
--- /dev/null
+++ b/src/test/ui/operator-recovery/spaceship.stderr
@@ -0,0 +1,8 @@
+error: invalid comparison operator `<=>`
+  --> $DIR/spaceship.rs:2:22
+   |
+LL |     println!("{}", 1 <=> 2);
+   |                      ^^^ `<=>` is not a valid comparison operator, use `std::cmp::Ordering`
+
+error: aborting due to previous error
+
diff --git a/src/test/ui/suggestions/suggest-add-self.rs b/src/test/ui/suggestions/suggest-add-self.rs
new file mode 100644
index 0000000000000..40692c8df2053
--- /dev/null
+++ b/src/test/ui/suggestions/suggest-add-self.rs
@@ -0,0 +1,15 @@
+struct X(i32);
+
+impl X {
+    pub(crate) fn f() {
+        self.0
+        //~^ ERROR expected value, found module `self`
+    }
+
+    pub fn g() {
+        self.0
+        //~^ ERROR expected value, found module `self`
+    }
+}
+
+fn main() {}
diff --git a/src/test/ui/suggestions/suggest-add-self.stderr b/src/test/ui/suggestions/suggest-add-self.stderr
new file mode 100644
index 0000000000000..a5e8f93deb64a
--- /dev/null
+++ b/src/test/ui/suggestions/suggest-add-self.stderr
@@ -0,0 +1,29 @@
+error[E0424]: expected value, found module `self`
+  --> $DIR/suggest-add-self.rs:5:9
+   |
+LL |     pub(crate) fn f() {
+   |                   - this function doesn't have a `self` parameter
+LL |         self.0
+   |         ^^^^ `self` value is a keyword only available in methods with a `self` parameter
+   |
+help: add a `self` receiver parameter to make the associated `fn` a method
+   |
+LL |     pub(crate) fn f(&self) {
+   |                     +++++
+
+error[E0424]: expected value, found module `self`
+  --> $DIR/suggest-add-self.rs:10:9
+   |
+LL |     pub fn g() {
+   |            - this function doesn't have a `self` parameter
+LL |         self.0
+   |         ^^^^ `self` value is a keyword only available in methods with a `self` parameter
+   |
+help: add a `self` receiver parameter to make the associated `fn` a method
+   |
+LL |     pub fn g(&self) {
+   |              +++++
+
+error: aborting due to 2 previous errors
+
+For more information about this error, try `rustc --explain E0424`.