Auto merge of #57617 - mark-i-m:multiple-matcher-bindings, r=petrochenkov

Error on duplicate matcher bindings

fix  #57593

This should not be merged without a crater run and maybe an FCP. Discussion is ongoing at  #57593.

TODO:
- [x] write tests
- [x] crater run
- [x] ~maybe need edition gating?~ not for 1 regression /centril

r? @petrochenkov

4 files changed, 86 insertions, 24 deletions

diff --git a/src/test/ui/macros/macro-follow.rs b/src/test/ui/macros/macro-follow.rs
index f4a1931da5a..10b44e00175 100644
--- a/src/test/ui/macros/macro-follow.rs
+++ b/src/test/ui/macros/macro-follow.rs
@@ -12,11 +12,11 @@ macro_rules! follow_pat {
     ($p:pat >) => {};        //~ERROR `$p:pat` is followed by `>`
     ($p:pat +) => {};        //~ERROR `$p:pat` is followed by `+`
     ($p:pat ident) => {};    //~ERROR `$p:pat` is followed by `ident`
-    ($p:pat $p:pat) => {};   //~ERROR `$p:pat` is followed by `$p:pat`
+    ($p:pat $q:pat) => {};   //~ERROR `$p:pat` is followed by `$q:pat`
     ($p:pat $e:expr) => {};  //~ERROR `$p:pat` is followed by `$e:expr`
     ($p:pat $t:ty) => {};    //~ERROR `$p:pat` is followed by `$t:ty`
     ($p:pat $s:stmt) => {};  //~ERROR `$p:pat` is followed by `$s:stmt`
-    ($p:pat $p:path) => {};  //~ERROR `$p:pat` is followed by `$p:path`
+    ($p:pat $q:path) => {};  //~ERROR `$p:pat` is followed by `$q:path`
     ($p:pat $b:block) => {}; //~ERROR `$p:pat` is followed by `$b:block`
     ($p:pat $i:ident) => {}; //~ERROR `$p:pat` is followed by `$i:ident`
     ($p:pat $t:tt) => {};    //~ERROR `$p:pat` is followed by `$t:tt`
@@ -37,7 +37,7 @@ macro_rules! follow_expr {
     ($e:expr if) => {};       //~ERROR `$e:expr` is followed by `if`
     ($e:expr in) => {};       //~ERROR `$e:expr` is followed by `in`
     ($e:expr $p:pat) => {};   //~ERROR `$e:expr` is followed by `$p:pat`
-    ($e:expr $e:expr) => {};  //~ERROR `$e:expr` is followed by `$e:expr`
+    ($e:expr $f:expr) => {};  //~ERROR `$e:expr` is followed by `$f:expr`
     ($e:expr $t:ty) => {};    //~ERROR `$e:expr` is followed by `$t:ty`
     ($e:expr $s:stmt) => {};  //~ERROR `$e:expr` is followed by `$s:stmt`
     ($e:expr $p:path) => {};  //~ERROR `$e:expr` is followed by `$p:path`
@@ -57,12 +57,12 @@ macro_rules! follow_ty {
     ($t:ty if) => {};       //~ERROR `$t:ty` is followed by `if`
     ($t:ty $p:pat) => {};   //~ERROR `$t:ty` is followed by `$p:pat`
     ($t:ty $e:expr) => {};  //~ERROR `$t:ty` is followed by `$e:expr`
-    ($t:ty $t:ty) => {};    //~ERROR `$t:ty` is followed by `$t:ty`
+    ($t:ty $r:ty) => {};    //~ERROR `$t:ty` is followed by `$r:ty`
     ($t:ty $s:stmt) => {};  //~ERROR `$t:ty` is followed by `$s:stmt`
     ($t:ty $p:path) => {};  //~ERROR `$t:ty` is followed by `$p:path`
     ($t:ty $b:block) => {}; // ok (RFC 1494)
     ($t:ty $i:ident) => {}; //~ERROR `$t:ty` is followed by `$i:ident`
-    ($t:ty $t:tt) => {};    //~ERROR `$t:ty` is followed by `$t:tt`
+    ($t:ty $r:tt) => {};    //~ERROR `$t:ty` is followed by `$r:tt`
     ($t:ty $i:item) => {};  //~ERROR `$t:ty` is followed by `$i:item`
     ($t:ty $m:meta) => {};  //~ERROR `$t:ty` is followed by `$m:meta`
 }
@@ -82,7 +82,7 @@ macro_rules! follow_stmt {
     ($s:stmt $p:pat) => {};   //~ERROR `$s:stmt` is followed by `$p:pat`
     ($s:stmt $e:expr) => {};  //~ERROR `$s:stmt` is followed by `$e:expr`
     ($s:stmt $t:ty) => {};    //~ERROR `$s:stmt` is followed by `$t:ty`
-    ($s:stmt $s:stmt) => {};  //~ERROR `$s:stmt` is followed by `$s:stmt`
+    ($s:stmt $t:stmt) => {};  //~ERROR `$s:stmt` is followed by `$t:stmt`
     ($s:stmt $p:path) => {};  //~ERROR `$s:stmt` is followed by `$p:path`
     ($s:stmt $b:block) => {}; //~ERROR `$s:stmt` is followed by `$b:block`
     ($s:stmt $i:ident) => {}; //~ERROR `$s:stmt` is followed by `$i:ident`
@@ -97,11 +97,11 @@ macro_rules! follow_path {
     ($p:path +) => {};        //~ERROR `$p:path` is followed by `+`
     ($p:path ident) => {};    //~ERROR `$p:path` is followed by `ident`
     ($p:path if) => {};       //~ERROR `$p:path` is followed by `if`
-    ($p:path $p:pat) => {};   //~ERROR `$p:path` is followed by `$p:pat`
+    ($p:path $q:pat) => {};   //~ERROR `$p:path` is followed by `$q:pat`
     ($p:path $e:expr) => {};  //~ERROR `$p:path` is followed by `$e:expr`
     ($p:path $t:ty) => {};    //~ERROR `$p:path` is followed by `$t:ty`
     ($p:path $s:stmt) => {};  //~ERROR `$p:path` is followed by `$s:stmt`
-    ($p:path $p:path) => {};  //~ERROR `$p:path` is followed by `$p:path`
+    ($p:path $q:path) => {};  //~ERROR `$p:path` is followed by `$q:path`
     ($p:path $b:block) => {}; // ok (RFC 1494)
     ($p:path $i:ident) => {}; //~ERROR `$p:path` is followed by `$i:ident`
     ($p:path $t:tt) => {};    //~ERROR `$p:path` is followed by `$t:tt`
diff --git a/src/test/ui/macros/macro-follow.stderr b/src/test/ui/macros/macro-follow.stderr
index 4aea5cc5de6..e3302eac4ac 100644
--- a/src/test/ui/macros/macro-follow.stderr
+++ b/src/test/ui/macros/macro-follow.stderr
@@ -54,10 +54,10 @@ LL |     ($p:pat ident) => {};    //~ERROR `$p:pat` is followed by `ident`
    |
    = note: allowed there are: `=>`, `,`, `=`, `|`, `if` or `in`
 
-error: `$p:pat` is followed by `$p:pat`, which is not allowed for `pat` fragments
+error: `$p:pat` is followed by `$q:pat`, which is not allowed for `pat` fragments
   --> $DIR/macro-follow.rs:15:13
    |
-LL |     ($p:pat $p:pat) => {};   //~ERROR `$p:pat` is followed by `$p:pat`
+LL |     ($p:pat $q:pat) => {};   //~ERROR `$p:pat` is followed by `$q:pat`
    |             ^^^^^^ not allowed after `pat` fragments
    |
    = note: allowed there are: `=>`, `,`, `=`, `|`, `if` or `in`
@@ -86,10 +86,10 @@ LL |     ($p:pat $s:stmt) => {};  //~ERROR `$p:pat` is followed by `$s:stmt`
    |
    = note: allowed there are: `=>`, `,`, `=`, `|`, `if` or `in`
 
-error: `$p:pat` is followed by `$p:path`, which is not allowed for `pat` fragments
+error: `$p:pat` is followed by `$q:path`, which is not allowed for `pat` fragments
   --> $DIR/macro-follow.rs:19:13
    |
-LL |     ($p:pat $p:path) => {};  //~ERROR `$p:pat` is followed by `$p:path`
+LL |     ($p:pat $q:path) => {};  //~ERROR `$p:pat` is followed by `$q:path`
    |             ^^^^^^^ not allowed after `pat` fragments
    |
    = note: allowed there are: `=>`, `,`, `=`, `|`, `if` or `in`
@@ -230,10 +230,10 @@ LL |     ($e:expr $p:pat) => {};   //~ERROR `$e:expr` is followed by `$p:pat`
    |
    = note: allowed there are: `=>`, `,` or `;`
 
-error: `$e:expr` is followed by `$e:expr`, which is not allowed for `expr` fragments
+error: `$e:expr` is followed by `$f:expr`, which is not allowed for `expr` fragments
   --> $DIR/macro-follow.rs:40:14
    |
-LL |     ($e:expr $e:expr) => {};  //~ERROR `$e:expr` is followed by `$e:expr`
+LL |     ($e:expr $f:expr) => {};  //~ERROR `$e:expr` is followed by `$f:expr`
    |              ^^^^^^^ not allowed after `expr` fragments
    |
    = note: allowed there are: `=>`, `,` or `;`
@@ -350,10 +350,10 @@ LL |     ($t:ty $e:expr) => {};  //~ERROR `$t:ty` is followed by `$e:expr`
    |
    = note: allowed there are: `{`, `[`, `=>`, `,`, `>`, `=`, `:`, `;`, `|`, `as` or `where`
 
-error: `$t:ty` is followed by `$t:ty`, which is not allowed for `ty` fragments
+error: `$t:ty` is followed by `$r:ty`, which is not allowed for `ty` fragments
   --> $DIR/macro-follow.rs:60:12
    |
-LL |     ($t:ty $t:ty) => {};    //~ERROR `$t:ty` is followed by `$t:ty`
+LL |     ($t:ty $r:ty) => {};    //~ERROR `$t:ty` is followed by `$r:ty`
    |            ^^^^^ not allowed after `ty` fragments
    |
    = note: allowed there are: `{`, `[`, `=>`, `,`, `>`, `=`, `:`, `;`, `|`, `as` or `where`
@@ -382,10 +382,10 @@ LL |     ($t:ty $i:ident) => {}; //~ERROR `$t:ty` is followed by `$i:ident`
    |
    = note: allowed there are: `{`, `[`, `=>`, `,`, `>`, `=`, `:`, `;`, `|`, `as` or `where`
 
-error: `$t:ty` is followed by `$t:tt`, which is not allowed for `ty` fragments
+error: `$t:ty` is followed by `$r:tt`, which is not allowed for `ty` fragments
   --> $DIR/macro-follow.rs:65:12
    |
-LL |     ($t:ty $t:tt) => {};    //~ERROR `$t:ty` is followed by `$t:tt`
+LL |     ($t:ty $r:tt) => {};    //~ERROR `$t:ty` is followed by `$r:tt`
    |            ^^^^^ not allowed after `ty` fragments
    |
    = note: allowed there are: `{`, `[`, `=>`, `,`, `>`, `=`, `:`, `;`, `|`, `as` or `where`
@@ -518,10 +518,10 @@ LL |     ($s:stmt $t:ty) => {};    //~ERROR `$s:stmt` is followed by `$t:ty`
    |
    = note: allowed there are: `=>`, `,` or `;`
 
-error: `$s:stmt` is followed by `$s:stmt`, which is not allowed for `stmt` fragments
+error: `$s:stmt` is followed by `$t:stmt`, which is not allowed for `stmt` fragments
   --> $DIR/macro-follow.rs:85:14
    |
-LL |     ($s:stmt $s:stmt) => {};  //~ERROR `$s:stmt` is followed by `$s:stmt`
+LL |     ($s:stmt $t:stmt) => {};  //~ERROR `$s:stmt` is followed by `$t:stmt`
    |              ^^^^^^^ not allowed after `stmt` fragments
    |
    = note: allowed there are: `=>`, `,` or `;`
@@ -606,10 +606,10 @@ LL |     ($p:path if) => {};       //~ERROR `$p:path` is followed by `if`
    |
    = note: allowed there are: `{`, `[`, `=>`, `,`, `>`, `=`, `:`, `;`, `|`, `as` or `where`
 
-error: `$p:path` is followed by `$p:pat`, which is not allowed for `path` fragments
+error: `$p:path` is followed by `$q:pat`, which is not allowed for `path` fragments
   --> $DIR/macro-follow.rs:100:14
    |
-LL |     ($p:path $p:pat) => {};   //~ERROR `$p:path` is followed by `$p:pat`
+LL |     ($p:path $q:pat) => {};   //~ERROR `$p:path` is followed by `$q:pat`
    |              ^^^^^^ not allowed after `path` fragments
    |
    = note: allowed there are: `{`, `[`, `=>`, `,`, `>`, `=`, `:`, `;`, `|`, `as` or `where`
@@ -638,10 +638,10 @@ LL |     ($p:path $s:stmt) => {};  //~ERROR `$p:path` is followed by `$s:stmt`
    |
    = note: allowed there are: `{`, `[`, `=>`, `,`, `>`, `=`, `:`, `;`, `|`, `as` or `where`
 
-error: `$p:path` is followed by `$p:path`, which is not allowed for `path` fragments
+error: `$p:path` is followed by `$q:path`, which is not allowed for `path` fragments
   --> $DIR/macro-follow.rs:104:14
    |
-LL |     ($p:path $p:path) => {};  //~ERROR `$p:path` is followed by `$p:path`
+LL |     ($p:path $q:path) => {};  //~ERROR `$p:path` is followed by `$q:path`
    |              ^^^^^^^ not allowed after `path` fragments
    |
    = note: allowed there are: `{`, `[`, `=>`, `,`, `>`, `=`, `:`, `;`, `|`, `as` or `where`
diff --git a/src/test/ui/macros/macro-multiple-matcher-bindings.rs b/src/test/ui/macros/macro-multiple-matcher-bindings.rs
new file mode 100644
index 00000000000..9e0fa388716
--- /dev/null
+++ b/src/test/ui/macros/macro-multiple-matcher-bindings.rs
@@ -0,0 +1,25 @@
+// Test that duplicate matcher binding names are caught at declaration time, rather than at macro
+// invocation time.
+//
+// FIXME(mark-i-m): Update this when it becomes a hard error.
+
+// compile-pass
+
+#![allow(unused_macros)]
+
+macro_rules! foo1 {
+    ($a:ident, $a:ident) => {}; //~WARNING duplicate matcher binding
+    ($a:ident, $a:path) => {};  //~WARNING duplicate matcher binding
+}
+
+macro_rules! foo2 {
+    ($a:ident) => {}; // OK
+    ($a:path) => {};  // OK
+}
+
+macro_rules! foo3 {
+    ($a:ident, $($a:ident),*) => {}; //~WARNING duplicate matcher binding
+    ($($a:ident)+ # $($($a:path),+);*) => {}; //~WARNING duplicate matcher binding
+}
+
+fn main() {}
diff --git a/src/test/ui/macros/macro-multiple-matcher-bindings.stderr b/src/test/ui/macros/macro-multiple-matcher-bindings.stderr
new file mode 100644
index 00000000000..bc78b471a2d
--- /dev/null
+++ b/src/test/ui/macros/macro-multiple-matcher-bindings.stderr
@@ -0,0 +1,37 @@
+warning: duplicate matcher binding
+  --> $DIR/macro-multiple-matcher-bindings.rs:11:6
+   |
+LL |     ($a:ident, $a:ident) => {}; //~WARNING duplicate matcher binding
+   |      ^^^^^^^^  ^^^^^^^^
+   |
+   = note: #[warn(duplicate_matcher_binding_name)] on by default
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #57593 <https://github.com/rust-lang/rust/issues/57593>
+
+warning: duplicate matcher binding
+  --> $DIR/macro-multiple-matcher-bindings.rs:12:6
+   |
+LL |     ($a:ident, $a:path) => {};  //~WARNING duplicate matcher binding
+   |      ^^^^^^^^  ^^^^^^^
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #57593 <https://github.com/rust-lang/rust/issues/57593>
+
+warning: duplicate matcher binding
+  --> $DIR/macro-multiple-matcher-bindings.rs:21:6
+   |
+LL |     ($a:ident, $($a:ident),*) => {}; //~WARNING duplicate matcher binding
+   |      ^^^^^^^^    ^^^^^^^^
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #57593 <https://github.com/rust-lang/rust/issues/57593>
+
+warning: duplicate matcher binding
+  --> $DIR/macro-multiple-matcher-bindings.rs:22:8
+   |
+LL |     ($($a:ident)+ # $($($a:path),+);*) => {}; //~WARNING duplicate matcher binding
+   |        ^^^^^^^^         ^^^^^^^
+   |
+   = warning: this was previously accepted by the compiler but is being phased out; it will become a hard error in a future release!
+   = note: for more information, see issue #57593 <https://github.com/rust-lang/rust/issues/57593>
+