From e846a863ac5c9ea35ca2439b1f76ac20d4cfca5a Mon Sep 17 00:00:00 2001
From: Mark Rousskov <mark.simulacrum@gmail.com>
Date: Fri, 2 Oct 2020 11:43:28 -0400
Subject: [PATCH] Revert "Remove missing_fragment_specifier lint"

This reverts commit 5ba961018c482e050af908de60e4f8bd1a00f0ae.
---
 src/doc/rustc/src/lints/listing/deny-by-default.md |  9 +++++++++
 src/librustc_session/lint/builtin.rs               | 11 +++++++++++
 2 files changed, 20 insertions(+)

diff --git a/src/doc/rustc/src/lints/listing/deny-by-default.md b/src/doc/rustc/src/lints/listing/deny-by-default.md
index 55714f8f4548b..dc5a9e44acfa2 100644
--- a/src/doc/rustc/src/lints/listing/deny-by-default.md
+++ b/src/doc/rustc/src/lints/listing/deny-by-default.md
@@ -45,6 +45,15 @@ error: defaults for type parameters are only allowed in `struct`, `enum`, `type`
   = note: for more information, see issue #36887 <https://github.com/rust-lang/rust/issues/36887>
 ```
 
+## missing-fragment-specifier
+
+The missing_fragment_specifier warning is issued when an unused pattern in a
+`macro_rules!` macro definition has a meta-variable (e.g. `$e`) that is not
+followed by a fragment specifier (e.g. `:expr`).
+
+This warning can always be fixed by removing the unused pattern in the
+`macro_rules!` macro definition.
+
 ## mutable-transmutes
 
 This lint catches transmuting from `&T` to `&mut T` because it is undefined
diff --git a/src/librustc_session/lint/builtin.rs b/src/librustc_session/lint/builtin.rs
index 2db4d2a7f51d9..144a06a4916bd 100644
--- a/src/librustc_session/lint/builtin.rs
+++ b/src/librustc_session/lint/builtin.rs
@@ -252,6 +252,16 @@ declare_lint! {
     };
 }
 
+declare_lint! {
+    pub MISSING_FRAGMENT_SPECIFIER,
+    Deny,
+    "detects missing fragment specifiers in unused `macro_rules!` patterns",
+    @future_incompatible = FutureIncompatibleInfo {
+        reference: "issue #40107 <https://github.com/rust-lang/rust/issues/40107>",
+        edition: None,
+    };
+}
+
 declare_lint! {
     pub LATE_BOUND_LIFETIME_ARGUMENTS,
     Warn,
@@ -574,6 +584,7 @@ declare_lint_pass! {
         UNALIGNED_REFERENCES,
         SAFE_PACKED_BORROWS,
         PATTERNS_IN_FNS_WITHOUT_BODY,
+        MISSING_FRAGMENT_SPECIFIER,
         LATE_BOUND_LIFETIME_ARGUMENTS,
         ORDER_DEPENDENT_TRAIT_OBJECTS,
         COHERENCE_LEAK_CHECK,