From 248d1b3de9872c21df3a92dbaff5c81e2026e0dc Mon Sep 17 00:00:00 2001
From: neis <neis@chromium.org>
Date: Tue, 17 Jan 2017 02:40:00 -0800
Subject: [PATCH] [parser] Pessimistically assume top-level variables will be
 assigned.

We have to pessimistically assume that top-level variables will be assigned.
This is because there may be lazily parsed top-level functions, which, for
efficiency, we preparse without variable tracking.

R=adamk@chromium.org, marja@chromium.org
CC=jarin@chromium.org
BUG=v8:5636

Review-Url: https://codereview.chromium.org/2634123002
Cr-Commit-Position: refs/heads/master@{#42398}
---
 src/parsing/pattern-rewriter.cc |  8 +++++
 test/cctest/test-parsing.cc     | 60 +++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+)

diff --git a/src/parsing/pattern-rewriter.cc b/src/parsing/pattern-rewriter.cc
index edd283e9d6..9eb3f0665b 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
+        // 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();
diff --git a/test/cctest/test-parsing.cc b/test/cctest/test-parsing.cc
index d668dd377b..06dcc3a1c9 100644
--- a/test/cctest/test-parsing.cc
+++ b/test/cctest/test-parsing.cc
@@ -3515,6 +3515,66 @@ TEST(MaybeAssignedParameters) {
   }
 }
 
+TEST(MaybeAssignedTopLevel) {
+  i::Isolate* isolate = CcTest::i_isolate();
+  i::HandleScope scope(isolate);
+  LocalContext env;
+  i::Factory* factory = isolate->factory();
+
+  const char* prefixes[] = {
+      "let foo; ",          "let foo = 0; ",
+      "let [foo] = [1]; ",  "let {foo} = {foo: 2}; ",
+      "let {foo=3} = {}; ",
+  };
+  const char* sources[] = {
+      "function bar() {foo = 42}; ext(bar); ext(foo)",
+      "ext(function() {foo++}); ext(foo)",
+      "bar = () => --foo; ext(bar); ext(foo)",
+      "function* bar() {eval(ext)}; ext(bar); ext(foo)",
+  };
+
+  for (unsigned i = 0; i < arraysize(prefixes); ++i) {
+    const char* prefix = prefixes[i];
+    for (unsigned j = 0; j < arraysize(sources); ++j) {
+      const char* source = sources[j];
+      i::ScopedVector<char> program(Utf8LengthHelper(prefix) +
+                                    Utf8LengthHelper(source) + 1);
+      i::SNPrintF(program, "%s%s", prefix, source);
+      i::Zone zone(isolate->allocator(), ZONE_NAME);
+
+      i::Handle<i::String> string =
+          factory->InternalizeUtf8String(program.start());
+      string->PrintOn(stdout);
+      printf("\n");
+      i::Handle<i::Script> script = factory->NewScript(string);
+
+      for (unsigned allow_lazy = 0; allow_lazy < 2; ++allow_lazy) {
+        for (unsigned module = 0; module < 2; ++module) {
+          std::unique_ptr<i::ParseInfo> info;
+          info = std::unique_ptr<i::ParseInfo>(new i::ParseInfo(&zone, script));
+          info->set_module(module);
+          info->set_allow_lazy_parsing(allow_lazy);
+
+          CHECK(i::parsing::ParseProgram(info.get()));
+          CHECK(i::Compiler::Analyze(info.get()));
+
+          CHECK_NOT_NULL(info->literal());
+          i::Scope* scope = info->literal()->scope();
+          CHECK(!scope->AsDeclarationScope()->was_lazily_parsed());
+          CHECK_NULL(scope->sibling());
+          CHECK(module ? scope->is_module_scope() : scope->is_script_scope());
+
+          const i::AstRawString* var_name =
+              info->ast_value_factory()->GetOneByteString("foo");
+          i::Variable* var = scope->Lookup(var_name);
+          CHECK(var->is_used());
+          CHECK(var->maybe_assigned() == i::kMaybeAssigned);
+        }
+      }
+    }
+  }
+}
+
 namespace {
 
 i::Scope* DeserializeFunctionScope(i::Isolate* isolate, i::Zone* zone,