Auto merge of #39419 - jseyfried:simplify_tokentree, r=nrc

Simplify `TokenTree` and fix `macro_rules!` bugs

This PR
 - fixes #39390, fixes #39403, and fixes #39404 (each is a [breaking-change], see issues for examples),
 - fixes #39889,
 - simplifies and optimizes macro invocation parsing,
 - cleans up `ext::tt::transcribe`,
 - removes `tokenstream::TokenTree::Sequence` and `Token::MatchNt`,
   - instead, adds a new type `ext::tt::quoted::TokenTree` for use by `macro_rules!` (`ext::tt`)
 - removes `parser.quote_depth` and `parser.parsing_token_tree`, and
 - removes `quote_matcher!`.
   - Instead, use `quote_tokens!` and `ext::tt::quoted::parse` the result with `expect_matchers=true`.
   - I found no outside uses of `quote_matcher!` when searching Rust code on Github.

r? @nrc

5 files changed, 12 insertions, 21 deletions

diff --git a/src/test/compile-fail/issue-35450.rs b/src/test/compile-fail/issue-35450.rs
index d890d02a910..5f54f269c6c 100644
--- a/src/test/compile-fail/issue-35450.rs
+++ b/src/test/compile-fail/issue-35450.rs
@@ -8,9 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-macro_rules! m { ($t:tt) => { $t } }
+macro_rules! m { ($($t:tt)*) => { $($t)* } }
 
 fn main() {
-    m!($t); //~ ERROR unknown macro variable
-            //~| ERROR expected expression
+    m!($t); //~ ERROR expected expression
 }
diff --git a/src/test/compile-fail/issue-39709.rs b/src/test/compile-fail/issue-39404.rs
index 0f66fe84393..0168ae7d910 100644
--- a/src/test/compile-fail/issue-39709.rs
+++ b/src/test/compile-fail/issue-39404.rs
@@ -8,8 +8,11 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-fn main() {
-    println!("{}", { macro_rules! x { ($()*) => {} } 33 });
-    //~^ ERROR no syntax variables matched as repeating at this depth
-}
+#![deny(missing_fragment_specifier)] //~ NOTE lint level defined here
 
+macro_rules! m { ($i) => {} }
+//~^ ERROR missing fragment specifier
+//~| WARN previously accepted
+//~| NOTE issue #40107
+
+fn main() {}
diff --git a/src/test/compile-fail/macro-error.rs b/src/test/compile-fail/macro-error.rs
index 78f95e365c4..82a5aa48729 100644
--- a/src/test/compile-fail/macro-error.rs
+++ b/src/test/compile-fail/macro-error.rs
@@ -9,7 +9,7 @@
 // except according to those terms.
 
 macro_rules! foo {
-    ($a:expr) => $a; //~ ERROR macro rhs must be delimited
+    ($a:expr) => a; //~ ERROR macro rhs must be delimited
 }
 
 fn main() {
diff --git a/src/test/compile-fail/macro-tt-matchers.rs b/src/test/compile-fail/macro-tt-matchers.rs
index 969f1500717..7255e7d00b6 100644
--- a/src/test/compile-fail/macro-tt-matchers.rs
+++ b/src/test/compile-fail/macro-tt-matchers.rs
@@ -17,16 +17,5 @@ macro_rules! foo {
 
 foo!(Box);
 
-macro_rules! bar {
-    ($x:tt) => {
-        macro_rules! baz {
-            ($x:tt, $y:tt) => { ($x, $y) }
-        }
-    }
-}
-
 #[rustc_error]
-fn main() { //~ ERROR compilation successful
-    bar!($y);
-    let _: (i8, i16) = baz!(0i8, 0i16);
-}
+fn main() {} //~ ERROR compilation successful
diff --git a/src/test/compile-fail/malformed_macro_lhs.rs b/src/test/compile-fail/malformed_macro_lhs.rs
index 5d81e21f056..0b437be5393 100644
--- a/src/test/compile-fail/malformed_macro_lhs.rs
+++ b/src/test/compile-fail/malformed_macro_lhs.rs
@@ -9,7 +9,7 @@
 // except according to those terms.
 
 macro_rules! my_precioooous {
-    $($t:tt)* => (1); //~ ERROR invalid macro matcher
+    t => (1); //~ ERROR invalid macro matcher
 }
 
 fn main() {