Account for maybe_whole_expr in range patterns.

2 files changed, 14 insertions, 0 deletions

diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 6cb965bf817..2fa6d20430b 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -3741,6 +3741,7 @@ impl<'a> Parser<'a> {
         self.token.is_path_start() // e.g. `MY_CONST`;
             || self.token == token::Dot // e.g. `.5` for recovery;
             || self.token.can_begin_literal_or_bool() // e.g. `42`.
+            || self.token.is_whole_expr()
     }
 
     // Helper function to decide whether to parse as ident binding
diff --git a/src/libsyntax/parse/token.rs b/src/libsyntax/parse/token.rs
index 472e4b474d6..d6d13c19f71 100644
--- a/src/libsyntax/parse/token.rs
+++ b/src/libsyntax/parse/token.rs
@@ -476,6 +476,19 @@ impl Token {
         false
     }
 
+    /// Would `maybe_whole_expr` in `parser.rs` return `Ok(..)`?
+    /// That is, is this a pre-parsed expression dropped into the token stream
+    /// (which happens while parsing the result ofmacro expansion)?
+    crate fn is_whole_expr(&self) -> bool {
+        if let Interpolated(ref nt) = self.kind {
+            if let NtExpr(_) | NtLiteral(_) | NtPath(_) | NtBlock(_) = **nt {
+                return true;
+            }
+        }
+
+        false
+    }
+
     /// Returns `true` if the token is either the `mut` or `const` keyword.
     crate fn is_mutability(&self) -> bool {
         self.is_keyword(kw::Mut) ||