Rollup merge of rust-lang#58876 - estebank:numeric-lifetime, r=petroc…

…henkov

Parse lifetimes that start with a number and give specific error

Fix rust-lang#58786.

src/libsyntax/parse/lexer/mod.rs

@@ -1423,15 +1423,17 @@ impl<'a> StringReader<'a> {
 
  // If the character is an ident start not followed by another single
  // quote, then this is a lifetime name:
- if ident_start(Some(c2)) && !self.ch_is('\'') {
+ if (ident_start(Some(c2)) || c2.is_numeric()) && !self.ch_is('\'') {
  while ident_continue(self.ch) {
  self.bump();
  }
  // lifetimes shouldn't end with a single quote
  // if we find one, then this is an invalid character literal
  if self.ch_is('\'') {
- self.err_span_(start_with_quote, self.next_pos,
- "character literal may only contain one codepoint");
+ self.err_span_(
+ start_with_quote,
+ self.next_pos,
+ "character literal may only contain one codepoint");
  self.bump();
  return Ok(token::Literal(token::Err(Symbol::intern("??")), None))
 
@@ -1444,6 +1446,15 @@ impl<'a> StringReader<'a> {
  self.mk_ident(&format!("'{}", lifetime_name))
  });
 
+ if c2.is_numeric() {
+ // this is a recovered lifetime written `'1`, error but accept it
+ self.err_span_(
+ start_with_quote,
+ self.pos,
+ "lifetimes cannot start with a number",
+ );
+ }
+
  return Ok(token::Lifetime(ident));
  }
 
@@ -1873,6 +1884,7 @@ fn is_block_doc_comment(s: &str) -> bool {
  res
 }
 
+/// Determine whether `c` is a valid start for an ident.
 fn ident_start(c: Option<char>) -> bool {
  let c = match c {
  Some(c) => c,

src/test/ui/parser/numeric-lifetime.rs

@@ -0,0 +1,8 @@
+struct S<'1> { s: &'1 usize }
+//~^ ERROR lifetimes cannot start with a number
+//~| ERROR lifetimes cannot start with a number
+fn main() {
+ // verify that the parse error doesn't stop type checking
+ let x: usize = "";
+ //~^ ERROR mismatched types
+}

src/test/ui/parser/numeric-lifetime.stderr

@@ -0,0 +1,24 @@
+error: lifetimes cannot start with a number
+ --> $DIR/numeric-lifetime.rs:1:10
+ |
+LL | struct S<'1> { s: &'1 usize }
+ | ^^
+
+error: lifetimes cannot start with a number
+ --> $DIR/numeric-lifetime.rs:1:20
+ |
+LL | struct S<'1> { s: &'1 usize }
+ | ^^
+
+error[E0308]: mismatched types
+ --> $DIR/numeric-lifetime.rs:6:20
+ |
+LL | let x: usize = "";
+ | ^^ expected usize, found reference
+ |
+ = note: expected type `usize`
+ found type `&'static str`
+
+error: aborting due to 3 previous errors
+
+For more information about this error, try `rustc --explain E0308`.