Auto merge of #66927 - RalfJung:engines-dont-panic, r=oli-obk

[rust.git] / src / libfmt_macros / lib.rs

diff --git a/src/libfmt_macros/lib.rs b/src/libfmt_macros/lib.rs
index 24b19028ac1179e65cff77613606a4eb8666fd03..2ecbe770729b5b278f21213df8902e31104ef224 100644 (file)
--- a/src/libfmt_macros/lib.rs
+++ b/src/libfmt_macros/lib.rs
@@ -11,6 +11,7 @@
 #![feature(nll)]
 #![feature(rustc_private)]
 #![feature(unicode_internals)]
+#![feature(bool_to_option)]
 
 pub use Piece::*;
 pub use Position::*;
@@ -442,20 +443,9 @@ fn position(&mut self) -> Option<Position> {
             Some(ArgumentIs(i))
         } else {
             match self.cur.peek() {
-                Some(&(_, c)) if c.is_alphabetic() => {
+                Some(&(_, c)) if rustc_lexer::is_id_start(c) => {
                     Some(ArgumentNamed(Symbol::intern(self.word())))
                 }
-                Some(&(pos, c)) if c == '_' => {
-                    let invalid_name = self.string(pos);
-                    self.err_with_note(format!("invalid argument name `{}`", invalid_name),
-                                       "invalid argument name",
-                                       "argument names cannot start with an underscore",
-                                        self.to_span_index(pos).to(
-                                            self.to_span_index(pos + invalid_name.len())
-                                        ),
-                                        );
-                    Some(ArgumentNamed(Symbol::intern(invalid_name)))
-                },
 
                 // This is an `ArgumentNext`.
                 // Record the fact and do the resolution after parsing the
@@ -611,22 +601,34 @@ fn count(&mut self, start: usize) -> (Count, Option<InnerSpan>) {
     /// Rust identifier, except that it can't start with `_` character.
     fn word(&mut self) -> &'a str {
         let start = match self.cur.peek() {
-            Some(&(pos, c)) if c != '_' && rustc_lexer::is_id_start(c) => {
+            Some(&(pos, c)) if rustc_lexer::is_id_start(c) => {
                 self.cur.next();
                 pos
             }
             _ => {
-                return &self.input[..0];
+                return "";
             }
         };
+        let mut end = None;
         while let Some(&(pos, c)) = self.cur.peek() {
             if rustc_lexer::is_id_continue(c) {
                 self.cur.next();
             } else {
-                return &self.input[start..pos];
+                end = Some(pos);
+                break;
             }
         }
-        &self.input[start..self.input.len()]
+        let end = end.unwrap_or(self.input.len());
+        let word = &self.input[start..end];
+        if word == "_" {
+            self.err_with_note(
+                "invalid argument name `_`",
+                "invalid argument name",
+                "argument name cannot be a single underscore",
+                self.to_span_index(start).to(self.to_span_index(end)),
+            );
+        }
+        word
     }
 
     /// Optionally parses an integer at the current position. This doesn't deal
@@ -643,11 +645,7 @@ fn integer(&mut self) -> Option<usize> {
                 break;
             }
         }
-        if found {
-            Some(cur)
-        } else {
-            None
-        }
+        found.then_some(cur)
     }
 }