From a77a8aaa2e55c0591ee766f3ff2142a67439d243 Mon Sep 17 00:00:00 2001
From: Mazdak Farrokhzad <twingoow@gmail.com>
Date: Mon, 14 Oct 2019 16:57:18 +0200
Subject: [PATCH] syntax: add test for intersection pattern parser recovery

---
 src/test/ui/parser/intersection-patterns.rs   | 40 +++++++++++++++++++
 .../ui/parser/intersection-patterns.stderr    | 33 +++++++++++++++
 2 files changed, 73 insertions(+)
 create mode 100644 src/test/ui/parser/intersection-patterns.rs
 create mode 100644 src/test/ui/parser/intersection-patterns.stderr

diff --git a/src/test/ui/parser/intersection-patterns.rs b/src/test/ui/parser/intersection-patterns.rs
new file mode 100644
index 00000000000..1dda21519e3
--- /dev/null
+++ b/src/test/ui/parser/intersection-patterns.rs
@@ -0,0 +1,40 @@
+// This tests the parser recovery in `recover_intersection_pat`
+// and serves as a regression test for the diagnostics issue #65400.
+//
+// The general idea is that for `$pat_lhs @ $pat_rhs` where
+// `$pat_lhs` is not generated by `ref? mut? $ident` we want
+// to suggest either switching the order or note that intersection
+// patterns are not allowed.
+
+fn main() {
+    let s: Option<u8> = None;
+
+    match s {
+        Some(x) @ y => {}
+        //~^ ERROR pattern on wrong side of `@`
+        //~| pattern on the left, should be to the right
+        //~| binding on the right, should be to the left
+        //~| HELP switch the order
+        //~| SUGGESTION y@Some(x)
+        _ => {}
+    }
+
+    match s {
+        Some(x) @ Some(y) => {}
+        //~^ ERROR left-hand side of `@` must be a binding pattern
+        //~| interpreted as a pattern, not a binding
+        //~| also a pattern
+        //~| NOTE bindings are `x`, `mut x`, `ref x`, and `ref mut x`
+        _ => {}
+    }
+
+    match 2 {
+        1 ..= 5 @ e => {}
+        //~^ ERROR pattern on wrong side of `@`
+        //~| pattern on the left, should be to the right
+        //~| binding on the right, should be to the left
+        //~| HELP switch the order
+        //~| SUGGESTION e@1 ..=5
+        _ => {}
+    }
+}
diff --git a/src/test/ui/parser/intersection-patterns.stderr b/src/test/ui/parser/intersection-patterns.stderr
new file mode 100644
index 00000000000..03781f8fdee
--- /dev/null
+++ b/src/test/ui/parser/intersection-patterns.stderr
@@ -0,0 +1,33 @@
+error: pattern on wrong side of `@`
+  --> $DIR/intersection-patterns.rs:13:9
+   |
+LL |         Some(x) @ y => {}
+   |         -------^^^-
+   |         |         |
+   |         |         binding on the right, should be to the left
+   |         pattern on the left, should be to the right
+   |         help: switch the order: `y@Some(x)`
+
+error: left-hand side of `@` must be a binding pattern
+  --> $DIR/intersection-patterns.rs:23:9
+   |
+LL |         Some(x) @ Some(y) => {}
+   |         -------^^^-------
+   |         |         |
+   |         |         also a pattern
+   |         interpreted as a pattern, not a binding
+   |
+   = note: bindings are `x`, `mut x`, `ref x`, and `ref mut x`
+
+error: pattern on wrong side of `@`
+  --> $DIR/intersection-patterns.rs:32:9
+   |
+LL |         1 ..= 5 @ e => {}
+   |         -------^^^-
+   |         |         |
+   |         |         binding on the right, should be to the left
+   |         pattern on the left, should be to the right
+   |         help: switch the order: `e@1 ..=5`
+
+error: aborting due to 3 previous errors
+