Auto merge of #29780 - KyleMayes:quote-ext, r=nrc

This is my first code contribution to Rust, so I'm sure there are some issues with the changes I've made.

I've added the `quote_arg!`, `quote_block!`, `quote_path!`, and `quote_meta_item!` quasiquoting macros. From my experience trying to build AST in compiler plugins, I would like to be able to build any AST piece with a quasiquoting macro (e.g., `quote_struct_field!` or `quote_variant!`) and then use those AST pieces in other quasiquoting macros, but this pull request just adds some of the low-hanging fruit.

I'm not sure if these additions are desirable, and I'm sure these macros can be implemented in an external crate if not.

2 files changed, 21 insertions, 1 deletions

diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 1e38eebec5d..9219f05d99a 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -393,6 +393,22 @@ impl<'a> Parser<'a> {
         panictry!(self.parse_attribute(permit_inner))
     }
 
+    pub fn parse_arg_panic(&mut self) -> Arg {
+        panictry!(self.parse_arg())
+    }
+
+    pub fn parse_block_panic(&mut self) -> P<Block> {
+        panictry!(self.parse_block())
+    }
+
+    pub fn parse_meta_item_panic(&mut self) -> P<ast::MetaItem> {
+        panictry!(self.parse_meta_item())
+    }
+
+    pub fn parse_path_panic(&mut self, mode: PathParsingMode) -> ast::Path {
+        panictry!(self.parse_path(mode))
+    }
+
     /// Convert a token to a string using self's reader
     pub fn token_to_string(token: &token::Token) -> String {
         pprust::token_to_string(token)
@@ -1455,6 +1471,8 @@ impl<'a> Parser<'a> {
     /// This version of parse arg doesn't necessarily require
     /// identifier names.
     pub fn parse_arg_general(&mut self, require_name: bool) -> PResult<Arg> {
+        maybe_whole!(no_clone self, NtArg);
+
         let pat = if require_name || self.is_named_argument() {
             debug!("parse_arg_general parse_pat (require_name:{})",
                    require_name);
diff --git a/src/libsyntax/parse/token.rs b/src/libsyntax/parse/token.rs
index ba24dc3c0a7..5e4449af604 100644
--- a/src/libsyntax/parse/token.rs
+++ b/src/libsyntax/parse/token.rs
@@ -381,12 +381,13 @@ pub enum Nonterminal {
     NtMeta(P<ast::MetaItem>),
     NtPath(Box<ast::Path>),
     NtTT(P<ast::TokenTree>), // needs P'ed to break a circularity
-    // These is not exposed to macros, but is used by quasiquote.
+    // These are not exposed to macros, but are used by quasiquote.
     NtArm(ast::Arm),
     NtImplItem(P<ast::ImplItem>),
     NtTraitItem(P<ast::TraitItem>),
     NtGenerics(ast::Generics),
     NtWhereClause(ast::WhereClause),
+    NtArg(ast::Arg),
 }
 
 impl fmt::Debug for Nonterminal {
@@ -407,6 +408,7 @@ impl fmt::Debug for Nonterminal {
             NtTraitItem(..) => f.pad("NtTraitItem(..)"),
             NtGenerics(..) => f.pad("NtGenerics(..)"),
             NtWhereClause(..) => f.pad("NtWhereClause(..)"),
+            NtArg(..) => f.pad("NtArg(..)"),
         }
     }
 }