Auto merge of #36154 - nrc:proc-macro-init, r=@jseyfried

Adds a `ProcMacro` form of syntax extension

This commit adds syntax extension forms matching the types for procedural macros 2.0 (RFC #1566), these still require the usual syntax extension boiler plate, but this is a first step towards proper implementation and should be useful for macros 1.1 stuff too.

Supports both attribute-like and function-like macros.

Note that RFC #1566 has not been accepted yet, but I think there is consensus that we want to head in vaguely that direction and so this PR will be useful in any case. It is also fairly easy to undo and does not break any existing programs.

This is related to #35957 in that I hope it can be used in the implementation of macros 1.1, however, there is no direct overlap and is more of a complement than a competing proposal. There is still a fair bit of work to do before the two can be combined.

r? @jseyfried

cc @alexcrichton, @cgswords, @eddyb, @aturon

1 files changed, 20 insertions, 7 deletions

diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 5cd4a046577..23085fadc5e 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -3872,15 +3872,17 @@ impl<'a> Parser<'a> {
         }
     }
 
-    fn parse_stmt_(&mut self, macro_expanded: bool) -> Option<Stmt> {
-        self.parse_stmt_without_recovery(macro_expanded).unwrap_or_else(|mut e| {
+    fn parse_stmt_(&mut self, macro_legacy_warnings: bool) -> Option<Stmt> {
+        self.parse_stmt_without_recovery(macro_legacy_warnings).unwrap_or_else(|mut e| {
             e.emit();
             self.recover_stmt_(SemiColonMode::Break);
             None
         })
     }
 
-    fn parse_stmt_without_recovery(&mut self, macro_expanded: bool) -> PResult<'a, Option<Stmt>> {
+    fn parse_stmt_without_recovery(&mut self,
+                                   macro_legacy_warnings: bool)
+                                   -> PResult<'a, Option<Stmt>> {
         maybe_whole!(Some deref self, NtStmt);
 
         let attrs = self.parse_outer_attributes()?;
@@ -3950,7 +3952,7 @@ impl<'a> Parser<'a> {
                 // We used to incorrectly stop parsing macro-expanded statements here.
                 // If the next token will be an error anyway but could have parsed with the
                 // earlier behavior, stop parsing here and emit a warning to avoid breakage.
-                else if macro_expanded && self.token.can_begin_expr() && match self.token {
+                else if macro_legacy_warnings && self.token.can_begin_expr() && match self.token {
                     // These can continue an expression, so we can't stop parsing and warn.
                     token::OpenDelim(token::Paren) | token::OpenDelim(token::Bracket) |
                     token::BinOp(token::Minus) | token::BinOp(token::Star) |
@@ -4125,8 +4127,8 @@ impl<'a> Parser<'a> {
     }
 
     /// Parse a statement, including the trailing semicolon.
-    pub fn parse_full_stmt(&mut self, macro_expanded: bool) -> PResult<'a, Option<Stmt>> {
-        let mut stmt = match self.parse_stmt_(macro_expanded) {
+    pub fn parse_full_stmt(&mut self, macro_legacy_warnings: bool) -> PResult<'a, Option<Stmt>> {
+        let mut stmt = match self.parse_stmt_(macro_legacy_warnings) {
             Some(stmt) => stmt,
             None => return Ok(None),
         };
@@ -4146,7 +4148,7 @@ impl<'a> Parser<'a> {
             }
             StmtKind::Local(..) => {
                 // We used to incorrectly allow a macro-expanded let statement to lack a semicolon.
-                if macro_expanded && self.token != token::Semi {
+                if macro_legacy_warnings && self.token != token::Semi {
                     self.warn_missing_semicolon();
                 } else {
                     self.expect_one_of(&[token::Semi], &[])?;
@@ -6169,4 +6171,15 @@ impl<'a> Parser<'a> {
             _ =>  Err(self.fatal("expected string literal"))
         }
     }
+
+    pub fn ensure_complete_parse<F>(&mut self, allow_semi: bool, on_err: F)
+        where F: FnOnce(&Parser)
+    {
+        if allow_semi && self.token == token::Semi {
+            self.bump();
+        }
+        if self.token != token::Eof {
+            on_err(self);
+        }
+    }
 }