[parser] Pessimistically assume top-level variables will be assigned.

src/parsing/pattern-rewriter.cc

Index: src/parsing/pattern-rewriter.cc
diff --git a/src/parsing/pattern-rewriter.cc b/src/parsing/pattern-rewriter.cc
index edd283e9d62f7a484b4f16a7149b0ab4d7903ae2..9eb3f0665be3030344a7fc4522310b6159eb2e77 100644
--- a/src/parsing/pattern-rewriter.cc
+++ b/src/parsing/pattern-rewriter.cc
@@ -224,6 +224,14 @@ void Parser::PatternRewriter::VisitVariableProxy(VariableProxy* pattern) {
     } else {
       DCHECK_NOT_NULL(proxy);
       DCHECK_NOT_NULL(proxy->var());
+      if (var_init_scope->is_script_scope() ||
+          var_init_scope->is_module_scope()) {
+        // We have to pessimistically assume that top-level variables will be
+        // assigned.  This is because there may be lazily parsed top-level

[adamk, 2017/01/17 18:09:04]

As discussed offline, this comment is slightly misleading: top-level variables
need to be marked as assigned because a script (or indirect eval) could always
modify them (unless they're CONST, naturally).

+        // functions, which, for efficiency, we preparse without variable
+        // tracking.
+        proxy->set_is_assigned();
+      }
     }
     // Add break location for destructured sub-pattern.
     int pos = IsSubPattern() ? pattern->position() : value->position();