Interpolate AST nodes in quasiquote.

This changes the `ToTokens` implementations for expressions, statements,
etc. with almost-trivial ones that produce `Interpolated(*Nt(...))`
pseudo-tokens. In this way, quasiquote now works the same way as macros
do: already-parsed AST fragments are used as-is, not reparsed.

The `ToSource` trait is removed. Quasiquote no longer involves
pretty-printing at all, which removes the need for the
`encode_with_hygiene` hack. All associated machinery is removed.

A new `Nonterminal` is added, NtArm, which the parser now interpolates.
This is just for quasiquote, not macros (although it could be in the
future).

`ToTokens` is no longer implemented for `Arg` (although this could be
added again) and `Generics` (which I don't think makes sense).

This breaks any compiler extensions that relied on the ability of
`ToTokens` to turn AST fragments back into inspectable token trees. For
this reason, this closes #16987.

As such, this is a [breaking-change].

Fixes #16472.
Fixes #15962.
Fixes #17397.
Fixes #16617.

1 files changed, 0 insertions, 72 deletions

diff --git a/src/libsyntax/parse/mod.rs b/src/libsyntax/parse/mod.rs
index dee3e5fee74..8c9ce5f78d4 100644
--- a/src/libsyntax/parse/mod.rs
+++ b/src/libsyntax/parse/mod.rs
@@ -166,9 +166,6 @@ pub fn parse_stmt_from_source_str(name: String,
     maybe_aborted(p.parse_stmt(), p)
 }
 
-// Note: keep in sync with `with_hygiene::parse_tts_from_source_str`
-// until #16472 is resolved.
-//
 // Warning: This parses with quote_depth > 0, which is not the default.
 pub fn parse_tts_from_source_str(name: String,
                                  source: String,
@@ -186,8 +183,6 @@ pub fn parse_tts_from_source_str(name: String,
     maybe_aborted(panictry!(p.parse_all_token_trees()),p)
 }
 
-// Note: keep in sync with `with_hygiene::new_parser_from_source_str`
-// until #16472 is resolved.
 // Create a new parser from a source string
 pub fn new_parser_from_source_str<'a>(sess: &'a ParseSess,
                                       cfg: ast::CrateConfig,
@@ -220,8 +215,6 @@ pub fn new_sub_parser_from_file<'a>(sess: &'a ParseSess,
     p
 }
 
-// Note: keep this in sync with `with_hygiene::filemap_to_parser` until
-// #16472 is resolved.
 /// Given a filemap and config, return a parser
 pub fn filemap_to_parser<'a>(sess: &'a ParseSess,
                              filemap: Rc<FileMap>,
@@ -277,8 +270,6 @@ pub fn string_to_filemap(sess: &ParseSess, source: String, path: String)
     sess.span_diagnostic.cm.new_filemap(path, source)
 }
 
-// Note: keep this in sync with `with_hygiene::filemap_to_tts` (apart
-// from the StringReader constructor), until #16472 is resolved.
 /// Given a filemap, produce a sequence of token-trees
 pub fn filemap_to_tts(sess: &ParseSess, filemap: Rc<FileMap>)
     -> Vec<ast::TokenTree> {
@@ -300,69 +291,6 @@ pub fn tts_to_parser<'a>(sess: &'a ParseSess,
     p
 }
 
-// FIXME (Issue #16472): The `with_hygiene` mod should go away after
-// ToToken impls are revised to go directly to token-trees.
-pub mod with_hygiene {
-    use ast;
-    use codemap::FileMap;
-    use parse::parser::Parser;
-    use std::rc::Rc;
-    use super::ParseSess;
-    use super::{maybe_aborted, string_to_filemap, tts_to_parser};
-
-    // Note: keep this in sync with `super::parse_tts_from_source_str` until
-    // #16472 is resolved.
-    //
-    // Warning: This parses with quote_depth > 0, which is not the default.
-    pub fn parse_tts_from_source_str(name: String,
-                                     source: String,
-                                     cfg: ast::CrateConfig,
-                                     sess: &ParseSess) -> Vec<ast::TokenTree> {
-        let mut p = new_parser_from_source_str(
-            sess,
-            cfg,
-            name,
-            source
-        );
-        p.quote_depth += 1;
-        // right now this is re-creating the token trees from ... token trees.
-        maybe_aborted(panictry!(p.parse_all_token_trees()),p)
-    }
-
-    // Note: keep this in sync with `super::new_parser_from_source_str` until
-    // #16472 is resolved.
-    // Create a new parser from a source string
-    fn new_parser_from_source_str<'a>(sess: &'a ParseSess,
-                                      cfg: ast::CrateConfig,
-                                      name: String,
-                                      source: String) -> Parser<'a> {
-        filemap_to_parser(sess, string_to_filemap(sess, source, name), cfg)
-    }
-
-    // Note: keep this in sync with `super::filemap_to_parserr` until
-    // #16472 is resolved.
-    /// Given a filemap and config, return a parser
-    fn filemap_to_parser<'a>(sess: &'a ParseSess,
-                             filemap: Rc<FileMap>,
-                             cfg: ast::CrateConfig) -> Parser<'a> {
-        tts_to_parser(sess, filemap_to_tts(sess, filemap), cfg)
-    }
-
-    // Note: keep this in sync with `super::filemap_to_tts` until
-    // #16472 is resolved.
-    /// Given a filemap, produce a sequence of token-trees
-    fn filemap_to_tts(sess: &ParseSess, filemap: Rc<FileMap>)
-                      -> Vec<ast::TokenTree> {
-        // it appears to me that the cfg doesn't matter here... indeed,
-        // parsing tt's probably shouldn't require a parser at all.
-        use super::lexer::make_reader_with_embedded_idents as make_reader;
-        let cfg = Vec::new();
-        let srdr = make_reader(&sess.span_diagnostic, filemap);
-        let mut p1 = Parser::new(sess, cfg, Box::new(srdr));
-        panictry!(p1.parse_all_token_trees())
-    }
-}
-
 /// Abort if necessary
 pub fn maybe_aborted<T>(result: T, p: Parser) -> T {
     p.abort_if_errors();