Fix comment typos

src/ast/scopes.cc

Index: src/ast/scopes.cc
diff --git a/src/ast/scopes.cc b/src/ast/scopes.cc
index 61fafb1ba18dad6dd7286bd22e899179ff067832..e7b785546e25fe4d684c444084ef970c32c01bd5 100644
--- a/src/ast/scopes.cc
+++ b/src/ast/scopes.cc
@@ -1451,8 +1451,7 @@ void Scope::Print(int n) {
 }
 
 void Scope::CheckScopePositions() {
-  // A scope is allowed to have invalid positions if it is hidden and has no
-  // inner scopes

[jwolfe, 2016/10/06 19:17:44]

The typo here is a bit subtle. A minimal change to correct it would be s/hidden
and has/hidden or has/, but i thought that was still too confusing. I changed
the logic in the comment to what I think is much easier to understand, as
opposed to simply translating the code in the if condition into English.

+  // Visible leaf scopes must have real positions.
   if (!is_hidden() && inner_scope_ == nullptr) {
     CHECK_NE(kNoSourcePosition, start_position());
     CHECK_NE(kNoSourcePosition, end_position());