Auto merge of #50971 - alexcrichton:no-stringify, r=petrochenkov

rustc: Correctly pretty-print macro delimiters

This commit updates the `Mac_` AST structure to keep track of the delimiters
that it originally had for its invocation. This allows us to faithfully
pretty-print macro invocations not using parentheses (e.g. `vec![...]`). This in
turn helps procedural macros due to #43081.

Closes #50840

src/test/ui-fulldeps/proc-macro/auxiliary/macro-brackets.rs

@@ -0,0 +1,22 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// no-prefer-dynamic
+
+#![crate_type = "proc-macro"]
+#![feature(proc_macro)]
+
+extern crate proc_macro;
+use proc_macro::*;
+
+#[proc_macro_attribute]
+pub fn doit(_: TokenStream, input: TokenStream) -> TokenStream {
+    input.into_iter().collect()
+}

src/test/ui-fulldeps/proc-macro/macro-brackets.rs

@@ -0,0 +1,26 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+// aux-build:macro-brackets.rs
+
+#![feature(proc_macro)]
+
+extern crate macro_brackets as bar;
+use bar::doit;
+
+macro_rules! id {
+    ($($t:tt)*) => ($($t)*)
+}
+
+#[doit]
+id![static X: u32 = 'a';]; //~ ERROR: mismatched types
+
+
+fn main() {}

src/test/ui-fulldeps/proc-macro/macro-brackets.stderr

@@ -0,0 +1,9 @@
+error[E0308]: mismatched types
+  --> $DIR/macro-brackets.rs:23:21
+   |
+LL | id![static X: u32 = 'a';]; //~ ERROR: mismatched types
+   |                     ^^^ expected u32, found char
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0308`.