From 480edb1151dcf2ef15e4f9501a60b9d71d63cac7 Mon Sep 17 00:00:00 2001
From: moonheart08 <moonheart08@users.noreply.github.com>
Date: Wed, 13 Oct 2021 19:50:26 -0500
Subject: [PATCH 1/2] Add an error for C++'s <=>

---
 compiler/rustc_parse/src/parser/expr.rs | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/compiler/rustc_parse/src/parser/expr.rs b/compiler/rustc_parse/src/parser/expr.rs
index 3d29d30502109..439b22aad2e86 100644
--- a/compiler/rustc_parse/src/parser/expr.rs
+++ b/compiler/rustc_parse/src/parser/expr.rs
@@ -213,6 +213,25 @@ impl<'a> Parser<'a> {
                 }
             }
 
+            if op.node == AssocOp::LessEqual
+                && self.token.kind == token::Gt
+                && self.prev_token.span.hi() == self.token.span.lo()
+            {
+                // Look for C++'s `<=>`
+                let sp = op.span.to(self.token.span);
+                self.struct_span_err(sp, &format!("invalid comparison operator `<=>`"))
+                    .span_suggestion_short(
+                        sp,
+                        &format!(
+                            "`<=>` is not a valid comparison operator, use std::cmp::Ordering"
+                        ),
+                        "<=>".to_string(),
+                        Applicability::Unspecified,
+                    )
+                    .emit();
+                self.bump();
+            }
+
             if (op.node == AssocOp::Equal || op.node == AssocOp::NotEqual)
                 && self.token.kind == token::Eq
                 && self.prev_token.span.hi() == self.token.span.lo()

From 4f1cb6e95e198fc2e4f408a69518c00b880655d7 Mon Sep 17 00:00:00 2001
From: moonheart08 <moonheart08@users.noreply.github.com>
Date: Wed, 13 Oct 2021 20:21:06 -0500
Subject: [PATCH 2/2] Tests for spaceship operator

---
 src/test/ui/spaceship-operator.rs     | 4 ++++
 src/test/ui/spaceship-operator.stderr | 8 ++++++++
 2 files changed, 12 insertions(+)
 create mode 100644 src/test/ui/spaceship-operator.rs
 create mode 100644 src/test/ui/spaceship-operator.stderr

diff --git a/src/test/ui/spaceship-operator.rs b/src/test/ui/spaceship-operator.rs
new file mode 100644
index 0000000000000..a65f9389625fc
--- /dev/null
+++ b/src/test/ui/spaceship-operator.rs
@@ -0,0 +1,4 @@
+fn main() {
+    println!("{}", 1 <=> 2);
+    //~^ERROR invalid comparison operator `<=>`
+}
diff --git a/src/test/ui/spaceship-operator.stderr b/src/test/ui/spaceship-operator.stderr
new file mode 100644
index 0000000000000..f32fb380eeb77
--- /dev/null
+++ b/src/test/ui/spaceship-operator.stderr
@@ -0,0 +1,8 @@
+error: invalid comparison operator `<=>`
+  --> $DIR/spaceship-operator.rs:2:22
+   |
+LL |     println!("{}", 1 <=> 2);
+   |                      ^^^ help: `<=>` is not a valid comparison operator, use std::cmp::Ordering
+
+error: aborting due to previous error
+