Reland of [parsing] Fix maybe-assigned for loop variables. (patchset #1 id:1...

Reland of [parsing] Fix maybe-assigned for loop variables. (patchset #1 id:1 of https://codereview.chromium.org/2679263002/ )

Reason for revert:
False alarm, bot hiccup

Original issue's description:
> Revert of [parsing] Fix maybe-assigned for loop variables. (patchset #3 id:40001 of https://codereview.chromium.org/2673403003/ )
>
> Reason for revert:
> Speculative revert because of https://codereview.chromium.org/2679163002/.
>
> Original issue's description:
> > [parsing] Fix maybe-assigned for loop variables.
> >
> > Due to hoisting, the value of a 'var'-declared variable may actually change even
> > if the code contains only the "initial" assignment, namely when that assignment
> > occurs inside a loop.  For example:
> >
> >   let i = 10;
> >   do { var x = i } while (i--):
> >
> > As a simple and very conservative approximation of this, we explicitly mark
> > as maybe-assigned any non-lexical variable whose "declaration" does not
> > syntactically occur in the function scope.  (In the example above, it
> > occurs in a block scope.)
> >
> > BUG=v8:5636
> >
> > Review-Url: https://codereview.chromium.org/2673403003
> > Cr-Commit-Position: refs/heads/master@{#42989}
> > Committed: https://chromium.googlesource.com/v8/v8/+/a33fcd663b28b8846e12b97c30d6e7d837767f86
>
> TBR=marja@chromium.org,adamk@chromium.org,neis@chromium.org
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=v8:5636
>
> Review-Url: https://codereview.chromium.org/2679263002
> Cr-Commit-Position: refs/heads/master@{#43010}
> Committed: https://chromium.googlesource.com/v8/v8/+/f3ae5ccf57690d8c2d87c4fe1d10b103ad6a4ab3

TBR=marja@chromium.org,adamk@chromium.org,neis@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=v8:5636

Review-Url: https://codereview.chromium.org/2686663002
Cr-Commit-Position: refs/heads/master@{#43013}

src/ast/scopes.h

@@ -181,6 +181,7 @@ class V8_EXPORT_PRIVATE Scope : public NON_EXPORTED_BASE(ZoneObject) {
                             bool* sloppy_mode_block_scope_function_redefinition,
                             bool* ok);
 
+  // The return value is meaningful only if FLAG_preparser_scope_analysis is on.
   Variable* DeclareVariableName(const AstRawString* name, VariableMode mode);
 
   // Declarations list.

src/parsing/parser-base.h

@@ -1347,6 +1347,24 @@ class ParserBase {
     return expression->IsObjectLiteral() || expression->IsArrayLiteral();
   }
 
+  // Due to hoisting, the value of a 'var'-declared variable may actually change
+  // even if the code contains only the "initial" assignment, namely when that
+  // assignment occurs inside a loop.  For example:
+  //
+  //   let i = 10;
+  //   do { var x = i } while (i--):
+  //
+  // As a simple and very conservative approximation of this, we explicitly mark
+  // as maybe-assigned any non-lexical variable whose initializing "declaration"
+  // does not syntactically occur in the function scope.  (In the example above,
+  // it occurs in a block scope.)
+  //
+  // Note that non-lexical variables include temporaries, which may also get
+  // assigned inside a loop due to the various rewritings that the parser
+  // performs.
+  //
+  static void MarkLoopVariableAsAssigned(Scope* scope, Variable* var);
+
   // Keep track of eval() calls since they disable all local variable
   // optimizations. This checks if expression is an eval call, and if yes,
   // forwards the information to scope.
@@ -5698,8 +5716,12 @@ typename ParserBase<Impl>::StatementT ParserBase<Impl>::ParseStandardForLoop(
   return loop;
 }
 
-#undef CHECK_OK
-#undef CHECK_OK_CUSTOM
+template <typename Impl>
+void ParserBase<Impl>::MarkLoopVariableAsAssigned(Scope* scope, Variable* var) {
+  if (!IsLexicalVariableMode(var->mode()) && !scope->is_function_scope()) {
+    var->set_maybe_assigned();
+  }
+}
 
 template <typename Impl>
 void ParserBase<Impl>::ObjectLiteralChecker::CheckDuplicateProto(
@@ -5751,6 +5773,8 @@ void ParserBase<Impl>::ClassLiteralChecker::CheckClassMethodName(
   }
 }
 
+#undef CHECK_OK
+#undef CHECK_OK_CUSTOM
 #undef CHECK_OK_VOID
 
 }  // namespace internal

src/parsing/pattern-rewriter.cc

@@ -177,6 +177,8 @@ void Parser::PatternRewriter::VisitVariableProxy(VariableProxy* pattern) {
   // If there's no initializer, we're done.
   if (value == nullptr) return;
 
+  MarkLoopVariableAsAssigned(var_init_scope, proxy->var());
+
   // A declaration of the form:
   //
   //    var v = x;

src/parsing/preparser.cc

@@ -310,8 +310,14 @@ void PreParser::DeclareAndInitializeVariables(
     DCHECK(track_unresolved_variables_);
     for (auto variable : *(declaration->pattern.variables_)) {
       declaration_descriptor->scope->RemoveUnresolved(variable);
-      scope()->DeclareVariableName(variable->raw_name(),
-                                   declaration_descriptor->mode);
+      Variable* var = scope()->DeclareVariableName(
+          variable->raw_name(), declaration_descriptor->mode);
+      if (FLAG_preparser_scope_analysis) {
+        MarkLoopVariableAsAssigned(declaration_descriptor->scope, var);
+        // This is only necessary if there is an initializer, but we don't have
+        // that information here.  Consequently, the preparser sometimes says
+        // maybe-assigned where the parser (correctly) says never-assigned.
+      }
       if (names) {
         names->Add(variable->raw_name(), zone());
       }

test/cctest/parsing/test-preparser.cc

@@ -30,268 +30,274 @@ TEST(PreParserScopeAnalysis) {
   const char* eager_inner = "(function inner(%s) { %s })()";
 
   struct {
+    bool precise_maybe_assigned;
     const char* params;
     const char* source;
   } inners[] = {
       // Simple cases
-      {"", "var1;"},
-      {"", "var1 = 5;"},
-      {"", "if (true) {}"},
-      {"", "function f1() {}"},
+      {1, "", "var1;"},
+      {1, "", "var1 = 5;"},
+      {1, "", "if (true) {}"},
+      {1, "", "function f1() {}"},
 
       // Var declarations and assignments.
-      {"", "var var1;"},
-      {"", "var var1; var1 = 5;"},
-      {"", "if (true) { var var1; }"},
-      {"", "if (true) { var var1; var1 = 5; }"},
-      {"", "var var1; function f() { var1; }"},
-      {"", "var var1; var1 = 5; function f() { var1; }"},
-      {"", "var var1; function f() { var1 = 5; }"},
+      {1, "", "var var1;"},
+      {1, "", "var var1; var1 = 5;"},
+      {0, "", "if (true) { var var1; }"},
+      {1, "", "if (true) { var var1; var1 = 5; }"},
+      {1, "", "var var1; function f() { var1; }"},
+      {1, "", "var var1; var1 = 5; function f() { var1; }"},
+      {1, "", "var var1; function f() { var1 = 5; }"},
 
       // Let declarations and assignments.
-      {"", "let var1;"},
-      {"", "let var1; var1 = 5;"},
-      {"", "if (true) { let var1; }"},
-      {"", "if (true) { let var1; var1 = 5; }"},
-      {"", "let var1; function f() { var1; }"},
-      {"", "let var1; var1 = 5; function f() { var1; }"},
-      {"", "let var1; function f() { var1 = 5; }"},
+      {1, "", "let var1;"},
+      {1, "", "let var1; var1 = 5;"},
+      {1, "", "if (true) { let var1; }"},
+      {1, "", "if (true) { let var1; var1 = 5; }"},
+      {1, "", "let var1; function f() { var1; }"},
+      {1, "", "let var1; var1 = 5; function f() { var1; }"},
+      {1, "", "let var1; function f() { var1 = 5; }"},
 
       // Const declarations.
-      {"", "const var1 = 5;"},
-      {"", "if (true) { const var1 = 5; }"},
-      {"", "const var1 = 5; function f() { var1; }"},
+      {1, "", "const var1 = 5;"},
+      {1, "", "if (true) { const var1 = 5; }"},
+      {1, "", "const var1 = 5; function f() { var1; }"},
 
       // Redeclarations.
-      {"", "var var1; var var1;"},
-      {"", "var var1; var var1; var1 = 5;"},
-      {"", "var var1; if (true) { var var1; }"},
-      {"", "if (true) { var var1; var var1; }"},
-      {"", "var var1; if (true) { var var1; var1 = 5; }"},
-      {"", "if (true) { var var1; var var1; var1 = 5; }"},
-      {"", "var var1; var var1; function f() { var1; }"},
-      {"", "var var1; var var1; function f() { var1 = 5; }"},
+      {1, "", "var var1; var var1;"},
+      {1, "", "var var1; var var1; var1 = 5;"},
+      {1, "", "var var1; if (true) { var var1; }"},
+      {1, "", "if (true) { var var1; var var1; }"},
+      {1, "", "var var1; if (true) { var var1; var1 = 5; }"},
+      {1, "", "if (true) { var var1; var var1; var1 = 5; }"},
+      {1, "", "var var1; var var1; function f() { var1; }"},
+      {1, "", "var var1; var var1; function f() { var1 = 5; }"},
 
       // Shadowing declarations.
-      {"", "var var1; if (true) { var var1; }"},
-      {"", "var var1; if (true) { let var1; }"},
-      {"", "let var1; if (true) { let var1; }"},
+      {1, "", "var var1; if (true) { var var1; }"},
+      {1, "", "var var1; if (true) { let var1; }"},
+      {1, "", "let var1; if (true) { let var1; }"},
 
-      {"", "var var1; if (true) { const var1 = 0; }"},
-      {"", "const var1 = 0; if (true) { const var1 = 0; }"},
+      {1, "", "var var1; if (true) { const var1 = 0; }"},
+      {1, "", "const var1 = 0; if (true) { const var1 = 0; }"},
 
       // Arguments and this.
-      {"", "arguments;"},
-      {"", "arguments = 5;"},
-      {"", "if (true) { arguments; }"},
-      {"", "if (true) { arguments = 5; }"},
-      {"", "function f() { arguments; }"},
-      {"", "function f() { arguments = 5; }"},
+      {1, "", "arguments;"},
+      {1, "", "arguments = 5;"},
+      {1, "", "if (true) { arguments; }"},
+      {1, "", "if (true) { arguments = 5; }"},
+      {1, "", "function f() { arguments; }"},
+      {1, "", "function f() { arguments = 5; }"},
 
-      {"", "this;"},
-      {"", "if (true) { this; }"},
-      {"", "function f() { this; }"},
+      {1, "", "this;"},
+      {1, "", "if (true) { this; }"},
+      {1, "", "function f() { this; }"},
 
       // Variable called "arguments"
-      {"", "var arguments;"},
-      {"", "var arguments; arguments = 5;"},
-      {"", "if (true) { var arguments; }"},
-      {"", "if (true) { var arguments; arguments = 5; }"},
-      {"", "var arguments; function f() { arguments; }"},
-      {"", "var arguments; arguments = 5; function f() { arguments; }"},
-      {"", "var arguments; function f() { arguments = 5; }"},
-
-      {"", "let arguments;"},
-      {"", "let arguments; arguments = 5;"},
-      {"", "if (true) { let arguments; }"},
-      {"", "if (true) { let arguments; arguments = 5; }"},
-      {"", "let arguments; function f() { arguments; }"},
-      {"", "let arguments; arguments = 5; function f() { arguments; }"},
-      {"", "let arguments; function f() { arguments = 5; }"},
-
-      {"", "const arguments = 5;"},
-      {"", "if (true) { const arguments = 5; }"},
-      {"", "const arguments = 5; function f() { arguments; }"},
+      {1, "", "var arguments;"},
+      {1, "", "var arguments; arguments = 5;"},
+      {0, "", "if (true) { var arguments; }"},
+      {1, "", "if (true) { var arguments; arguments = 5; }"},
+      {1, "", "var arguments; function f() { arguments; }"},
+      {1, "", "var arguments; arguments = 5; function f() { arguments; }"},
+      {1, "", "var arguments; function f() { arguments = 5; }"},
+
+      {1, "", "let arguments;"},
+      {1, "", "let arguments; arguments = 5;"},
+      {1, "", "if (true) { let arguments; }"},
+      {1, "", "if (true) { let arguments; arguments = 5; }"},
+      {1, "", "let arguments; function f() { arguments; }"},
+      {1, "", "let arguments; arguments = 5; function f() { arguments; }"},
+      {1, "", "let arguments; function f() { arguments = 5; }"},
+
+      {1, "", "const arguments = 5;"},
+      {1, "", "if (true) { const arguments = 5; }"},
+      {1, "", "const arguments = 5; function f() { arguments; }"},
 
       // Destructuring declarations.
-      {"", "var [var1, var2] = [1, 2];"},
-      {"", "var [var1, var2, [var3, var4]] = [1, 2, [3, 4]];"},
-      {"", "var [{var1: var2}, {var3: var4}] = [{var1: 1}, {var3: 2}];"},
-      {"", "var [var1, ...var2] = [1, 2, 3];"},
+      {1, "", "var [var1, var2] = [1, 2];"},
+      {1, "", "var [var1, var2, [var3, var4]] = [1, 2, [3, 4]];"},
+      {1, "", "var [{var1: var2}, {var3: var4}] = [{var1: 1}, {var3: 2}];"},
+      {1, "", "var [var1, ...var2] = [1, 2, 3];"},
 
-      {"", "var {var1: var2, var3: var4} = {var1: 1, var3: 2};"},
-      {"",
+      {1, "", "var {var1: var2, var3: var4} = {var1: 1, var3: 2};"},
+      {1, "",
        "var {var1: var2, var3: {var4: var5}} = {var1: 1, var3: {var4: 2}};"},
-      {"", "var {var1: var2, var3: [var4, var5]} = {var1: 1, var3: [2, 3]};"},
+      {1, "",
+       "var {var1: var2, var3: [var4, var5]} = {var1: 1, var3: [2, 3]};"},
 
-      {"", "let [var1, var2] = [1, 2];"},
-      {"", "let [var1, var2, [var3, var4]] = [1, 2, [3, 4]];"},
-      {"", "let [{var1: var2}, {var3: var4}] = [{var1: 1}, {var3: 2}];"},
-      {"", "let [var1, ...var2] = [1, 2, 3];"},
+      {1, "", "let [var1, var2] = [1, 2];"},
+      {1, "", "let [var1, var2, [var3, var4]] = [1, 2, [3, 4]];"},
+      {1, "", "let [{var1: var2}, {var3: var4}] = [{var1: 1}, {var3: 2}];"},
+      {1, "", "let [var1, ...var2] = [1, 2, 3];"},
 
-      {"", "let {var1: var2, var3: var4} = {var1: 1, var3: 2};"},
-      {"",
+      {1, "", "let {var1: var2, var3: var4} = {var1: 1, var3: 2};"},
+      {1, "",
        "let {var1: var2, var3: {var4: var5}} = {var1: 1, var3: {var4: 2}};"},
-      {"", "let {var1: var2, var3: [var4, var5]} = {var1: 1, var3: [2, 3]};"},
+      {1, "",
+       "let {var1: var2, var3: [var4, var5]} = {var1: 1, var3: [2, 3]};"},
 
-      {"", "const [var1, var2] = [1, 2];"},
-      {"", "const [var1, var2, [var3, var4]] = [1, 2, [3, 4]];"},
-      {"", "const [{var1: var2}, {var3: var4}] = [{var1: 1}, {var3: 2}];"},
-      {"", "const [var1, ...var2] = [1, 2, 3];"},
+      {1, "", "const [var1, var2] = [1, 2];"},
+      {1, "", "const [var1, var2, [var3, var4]] = [1, 2, [3, 4]];"},
+      {1, "", "const [{var1: var2}, {var3: var4}] = [{var1: 1}, {var3: 2}];"},
+      {1, "", "const [var1, ...var2] = [1, 2, 3];"},
 
-      {"", "const {var1: var2, var3: var4} = {var1: 1, var3: 2};"},
-      {"",
+      {1, "", "const {var1: var2, var3: var4} = {var1: 1, var3: 2};"},
+      {1, "",
        "const {var1: var2, var3: {var4: var5}} = {var1: 1, var3: {var4: 2}};"},
-      {"", "const {var1: var2, var3: [var4, var5]} = {var1: 1, var3: [2, 3]};"},
+      {1, "",
+       "const {var1: var2, var3: [var4, var5]} = {var1: 1, var3: [2, 3]};"},
 
       // Referencing the function variable.
-      {"", "inner;"},
-      {"", "function f1() { f1; }"},
-      {"", "function f1() { inner; }"},
-      {"", "function f1() { function f2() { f1; } }"},
-      {"", "function arguments() {}"},
-      {"", "function f1() {} function f1() {}"},
-      {"", "var f1; function f1() {}"},
+      {1, "", "inner;"},
+      {1, "", "function f1() { f1; }"},
+      {1, "", "function f1() { inner; }"},
+      {1, "", "function f1() { function f2() { f1; } }"},
+      {1, "", "function arguments() {}"},
+      {1, "", "function f1() {} function f1() {}"},
+      {1, "", "var f1; function f1() {}"},
 
       // Assigning to the function variable.
-      {"", "inner = 3;"},
-      {"", "function f1() { f1 = 3; }"},
-      {"", "function f1() { f1; } f1 = 3;"},
-      {"", "function arguments() {} arguments = 8"},
-      {"", "function f1() {} f1 = 3; function f1() {}"},
+      {1, "", "inner = 3;"},
+      {1, "", "function f1() { f1 = 3; }"},
+      {1, "", "function f1() { f1; } f1 = 3;"},
+      {1, "", "function arguments() {} arguments = 8"},
+      {1, "", "function f1() {} f1 = 3; function f1() {}"},
 
       // Evals.
-      {"", "var var1; eval('');"},
-      {"", "var var1; function f1() { eval(''); }"},
-      {"", "let var1; eval('');"},
-      {"", "let var1; function f1() { eval(''); }"},
-      {"", "const var1 = 10; eval('');"},
-      {"", "const var1 = 10; function f1() { eval(''); }"},
+      {1, "", "var var1; eval('');"},
+      {1, "", "var var1; function f1() { eval(''); }"},
+      {1, "", "let var1; eval('');"},
+      {1, "", "let var1; function f1() { eval(''); }"},
+      {1, "", "const var1 = 10; eval('');"},
+      {1, "", "const var1 = 10; function f1() { eval(''); }"},
 
       // Standard for loops.
-      {"", "for (var var1 = 0; var1 < 10; ++var1) { }"},
-      {"", "for (let var1 = 0; var1 < 10; ++var1) { }"},
-      {"", "for (const var1 = 0; var1 < 10; ++var1) { }"},
+      {1, "", "for (var var1 = 0; var1 < 10; ++var1) { }"},
+      {1, "", "for (let var1 = 0; var1 < 10; ++var1) { }"},
+      {1, "", "for (const var1 = 0; var1 < 10; ++var1) { }"},
 
-      {"",
+      {1, "",
        "for (var var1 = 0; var1 < 10; ++var1) { function foo() { var1; } }"},
-      {"",
+      {1, "",
        "for (let var1 = 0; var1 < 10; ++var1) { function foo() { var1; } }"},
-      {"",
+      {1, "",
        "for (const var1 = 0; var1 < 10; ++var1) { function foo() { var1; } }"},
-      {"",
+      {1, "",
        "'use strict'; for (var var1 = 0; var1 < 10; ++var1) { function foo() { "
        "var1; } }"},
-      {"",
+      {1, "",
        "'use strict'; for (let var1 = 0; var1 < 10; ++var1) { function foo() { "
        "var1; } }"},
-      {"",
+      {1, "",
        "'use strict'; for (const var1 = 0; var1 < 10; ++var1) { function foo() "
        "{ var1; } }"},
 
       // For of loops
-      {"", "for (var1 of [1, 2]) { }"},
-      {"", "for (var var1 of [1, 2]) { }"},
-      {"", "for (let var1 of [1, 2]) { }"},
-      {"", "for (const var1 of [1, 2]) { }"},
-
-      {"", "for (var1 of [1, 2]) { var1; }"},
-      {"", "for (var var1 of [1, 2]) { var1; }"},
-      {"", "for (let var1 of [1, 2]) { var1; }"},
-      {"", "for (const var1 of [1, 2]) { var1; }"},
-
-      {"", "for (var1 of [1, 2]) { var1 = 0; }"},
-      {"", "for (var var1 of [1, 2]) { var1 = 0; }"},
-      {"", "for (let var1 of [1, 2]) { var1 = 0; }"},
-      {"", "for (const var1 of [1, 2]) { var1 = 0; }"},
-
-      {"", "for (var1 of [1, 2]) { function foo() { var1; } }"},
-      {"", "for (var var1 of [1, 2]) { function foo() { var1; } }"},
-      {"", "for (let var1 of [1, 2]) { function foo() { var1; } }"},
-      {"", "for (const var1 of [1, 2]) { function foo() { var1; } }"},
-
-      {"", "for (var1 of [1, 2]) { function foo() { var1 = 0; } }"},
-      {"", "for (var var1 of [1, 2]) { function foo() { var1 = 0; } }"},
-      {"", "for (let var1 of [1, 2]) { function foo() { var1 = 0; } }"},
-      {"", "for (const var1 of [1, 2]) { function foo() { var1 = 0; } }"},
+      {1, "", "for (var1 of [1, 2]) { }"},
+      {1, "", "for (var var1 of [1, 2]) { }"},
+      {1, "", "for (let var1 of [1, 2]) { }"},
+      {1, "", "for (const var1 of [1, 2]) { }"},
+
+      {1, "", "for (var1 of [1, 2]) { var1; }"},
+      {1, "", "for (var var1 of [1, 2]) { var1; }"},
+      {1, "", "for (let var1 of [1, 2]) { var1; }"},
+      {1, "", "for (const var1 of [1, 2]) { var1; }"},
+
+      {1, "", "for (var1 of [1, 2]) { var1 = 0; }"},
+      {1, "", "for (var var1 of [1, 2]) { var1 = 0; }"},
+      {1, "", "for (let var1 of [1, 2]) { var1 = 0; }"},
+      {1, "", "for (const var1 of [1, 2]) { var1 = 0; }"},
+
+      {1, "", "for (var1 of [1, 2]) { function foo() { var1; } }"},
+      {1, "", "for (var var1 of [1, 2]) { function foo() { var1; } }"},
+      {1, "", "for (let var1 of [1, 2]) { function foo() { var1; } }"},
+      {1, "", "for (const var1 of [1, 2]) { function foo() { var1; } }"},
+
+      {1, "", "for (var1 of [1, 2]) { function foo() { var1 = 0; } }"},
+      {1, "", "for (var var1 of [1, 2]) { function foo() { var1 = 0; } }"},
+      {1, "", "for (let var1 of [1, 2]) { function foo() { var1 = 0; } }"},
+      {1, "", "for (const var1 of [1, 2]) { function foo() { var1 = 0; } }"},
 
       // For in loops
-      {"", "for (var1 in {a: 6}) { }"},
-      {"", "for (var var1 in {a: 6}) { }"},
-      {"", "for (let var1 in {a: 6}) { }"},
-      {"", "for (const var1 in {a: 6}) { }"},
-
-      {"", "for (var1 in {a: 6}) { var1; }"},
-      {"", "for (var var1 in {a: 6}) { var1; }"},
-      {"", "for (let var1 in {a: 6}) { var1; }"},
-      {"", "for (const var1 in {a: 6}) { var1; }"},
-
-      {"", "for (var1 in {a: 6}) { var1 = 0; }"},
-      {"", "for (var var1 in {a: 6}) { var1 = 0; }"},
-      {"", "for (let var1 in {a: 6}) { var1 = 0; }"},
-      {"", "for (const var1 in {a: 6}) { var1 = 0; }"},
-
-      {"", "for (var1 in {a: 6}) { function foo() { var1; } }"},
-      {"", "for (var var1 in {a: 6}) { function foo() { var1; } }"},
-      {"", "for (let var1 in {a: 6}) { function foo() { var1; } }"},
-      {"", "for (const var1 in {a: 6}) { function foo() { var1; } }"},
-
-      {"", "for (var1 in {a: 6}) { function foo() { var1 = 0; } }"},
-      {"", "for (var var1 in {a: 6}) { function foo() { var1 = 0; } }"},
-      {"", "for (let var1 in {a: 6}) { function foo() { var1 = 0; } }"},
-      {"", "for (const var1 in {a: 6}) { function foo() { var1 = 0; } }"},
-
-      {"", "for (var1 in {a: 6}) { function foo() { var1 = 0; } }"},
-      {"", "for (var var1 in {a: 6}) { function foo() { var1 = 0; } }"},
-      {"", "for (let var1 in {a: 6}) { function foo() { var1 = 0; } }"},
-      {"", "for (const var1 in {a: 6}) { function foo() { var1 = 0; } }"},
+      {1, "", "for (var1 in {a: 6}) { }"},
+      {1, "", "for (var var1 in {a: 6}) { }"},
+      {1, "", "for (let var1 in {a: 6}) { }"},
+      {1, "", "for (const var1 in {a: 6}) { }"},
+
+      {1, "", "for (var1 in {a: 6}) { var1; }"},
+      {1, "", "for (var var1 in {a: 6}) { var1; }"},
+      {1, "", "for (let var1 in {a: 6}) { var1; }"},
+      {1, "", "for (const var1 in {a: 6}) { var1; }"},
+
+      {1, "", "for (var1 in {a: 6}) { var1 = 0; }"},
+      {1, "", "for (var var1 in {a: 6}) { var1 = 0; }"},
+      {1, "", "for (let var1 in {a: 6}) { var1 = 0; }"},
+      {1, "", "for (const var1 in {a: 6}) { var1 = 0; }"},
+
+      {1, "", "for (var1 in {a: 6}) { function foo() { var1; } }"},
+      {1, "", "for (var var1 in {a: 6}) { function foo() { var1; } }"},
+      {1, "", "for (let var1 in {a: 6}) { function foo() { var1; } }"},
+      {1, "", "for (const var1 in {a: 6}) { function foo() { var1; } }"},
+
+      {1, "", "for (var1 in {a: 6}) { function foo() { var1 = 0; } }"},
+      {1, "", "for (var var1 in {a: 6}) { function foo() { var1 = 0; } }"},
+      {1, "", "for (let var1 in {a: 6}) { function foo() { var1 = 0; } }"},
+      {1, "", "for (const var1 in {a: 6}) { function foo() { var1 = 0; } }"},
+
+      {1, "", "for (var1 in {a: 6}) { function foo() { var1 = 0; } }"},
+      {1, "", "for (var var1 in {a: 6}) { function foo() { var1 = 0; } }"},
+      {1, "", "for (let var1 in {a: 6}) { function foo() { var1 = 0; } }"},
+      {1, "", "for (const var1 in {a: 6}) { function foo() { var1 = 0; } }"},
 
       // Loops without declarations
-      {"", "var var1 = 0; for ( ; var1 < 2; ++var1) { }"},
-      {"",
+      {1, "", "var var1 = 0; for ( ; var1 < 2; ++var1) { }"},
+      {1, "",
        "var var1 = 0; for ( ; var1 < 2; ++var1) { function foo() { var1; } }"},
-      {"", "var var1 = 0; for ( ; var1 > 2; ) { }"},
-      {"", "var var1 = 0; for ( ; var1 > 2; ) { function foo() { var1; } }"},
-      {"",
+      {1, "", "var var1 = 0; for ( ; var1 > 2; ) { }"},
+      {1, "", "var var1 = 0; for ( ; var1 > 2; ) { function foo() { var1; } }"},
+      {1, "",
        "var var1 = 0; for ( ; var1 > 2; ) { function foo() { var1 = 6; } }"},
 
-      {"", "var var1 = 0; for(var1; var1 < 2; ++var1) { }"},
-      {"",
+      {1, "", "var var1 = 0; for(var1; var1 < 2; ++var1) { }"},
+      {1, "",
        "var var1 = 0; for (var1; var1 < 2; ++var1) { function foo() { var1; } "
        "}"},
-      {"", "var var1 = 0; for (var1; var1 > 2; ) { }"},
-      {"", "var var1 = 0; for (var1; var1 > 2; ) { function foo() { var1; } }"},
-      {"",
+      {1, "", "var var1 = 0; for (var1; var1 > 2; ) { }"},
+      {1, "",
+       "var var1 = 0; for (var1; var1 > 2; ) { function foo() { var1; } }"},
+      {1, "",
        "var var1 = 0; for (var1; var1 > 2; ) { function foo() { var1 = 6; } }"},
 
       // Sloppy block functions.
-      {"", "if (true) { function f1() {} }"},
-      {"", "if (true) { function f1() {} function f1() {} }"},
-      {"", "if (true) { if (true) { function f1() {} } }"},
-      {"", "if (true) { if (true) { function f1() {} function f1() {} } }"},
-      {"", "if (true) { function f1() {} f1 = 3; }"},
-
-      {"", "if (true) { function f1() {} function foo() { f1; } }"},
-      {"", "if (true) { function f1() {} } function foo() { f1; }"},
-      {"",
+      {1, "", "if (true) { function f1() {} }"},
+      {1, "", "if (true) { function f1() {} function f1() {} }"},
+      {1, "", "if (true) { if (true) { function f1() {} } }"},
+      {1, "", "if (true) { if (true) { function f1() {} function f1() {} } }"},
+      {1, "", "if (true) { function f1() {} f1 = 3; }"},
+
+      {1, "", "if (true) { function f1() {} function foo() { f1; } }"},
+      {1, "", "if (true) { function f1() {} } function foo() { f1; }"},
+      {1, "",
        "if (true) { function f1() {} function f1() {} function foo() { f1; } "
        "}"},
-      {"",
+      {1, "",
        "if (true) { function f1() {} function f1() {} } function foo() { f1; "
        "}"},
-      {"",
+      {1, "",
        "if (true) { if (true) { function f1() {} } function foo() { f1; } }"},
-      {"",
+      {1, "",
        "if (true) { if (true) { function f1() {} function f1() {} } function "
        "foo() { f1; } }"},
-      {"", "if (true) { function f1() {} f1 = 3; function foo() { f1; } }"},
-      {"", "if (true) { function f1() {} f1 = 3; } function foo() { f1; }"},
+      {1, "", "if (true) { function f1() {} f1 = 3; function foo() { f1; } }"},
+      {1, "", "if (true) { function f1() {} f1 = 3; } function foo() { f1; }"},
 
-      {"", "function inner2() { if (true) { function f1() {} } }"},
-      {"", "function inner2() { if (true) { function f1() {} f1 = 3; } }"},
+      {1, "", "function inner2() { if (true) { function f1() {} } }"},
+      {1, "", "function inner2() { if (true) { function f1() {} f1 = 3; } }"},
 
-      {"", "var f1 = 1; if (true) { function f1() {} }"},
-      {"", "var f1 = 1; if (true) { function f1() {} } function foo() { f1; }"},
+      {1, "", "var f1 = 1; if (true) { function f1() {} }"},
+      {1, "",
+       "var f1 = 1; if (true) { function f1() {} } function foo() { f1; }"},
   };
 
   for (unsigned i = 0; i < arraysize(inners); ++i) {
@@ -358,6 +364,7 @@ TEST(PreParserScopeAnalysis) {
 
     size_t index = 0;
     i::ScopeTestHelper::CompareScopeToData(
-        scope, lazy_info.preparsed_scope_data(), index);
+        scope, lazy_info.preparsed_scope_data(), index,
+        inners[i].precise_maybe_assigned);
   }
 }

test/cctest/scope-test-helper.h

@@ -32,7 +32,7 @@ class ScopeTestHelper {
   }
 
   static void CompareScopeToData(Scope* scope, const PreParsedScopeData* data,
-                                 size_t& index) {
+                                 size_t& index, bool precise_maybe_assigned) {
     CHECK_EQ(data->backing_store_[index++], scope->scope_type());
     CHECK_EQ(data->backing_store_[index++], scope->start_position());
     CHECK_EQ(data->backing_store_[index++], scope->end_position());
@@ -70,14 +70,19 @@ class ScopeTestHelper {
         }
 #endif
         CHECK_EQ(data->backing_store_[index++], local->location());
+        if (precise_maybe_assigned) {
           CHECK_EQ(data->backing_store_[index++], local->maybe_assigned());
+        } else {
+          STATIC_ASSERT(kMaybeAssigned > kNotAssigned);
+          CHECK_GE(data->backing_store_[index++], local->maybe_assigned());
+        }
       }
     }
 
     for (Scope* inner = scope->inner_scope(); inner != nullptr;
          inner = inner->sibling()) {
       if (!ScopeTreeIsHidden(inner)) {
-        CompareScopeToData(inner, data, index);
+        CompareScopeToData(inner, data, index, precise_maybe_assigned);
       }
     }
   }

test/cctest/test-parsing.cc

@@ -3495,6 +3495,365 @@ TEST(MaybeAssignedParameters) {
   }
 }
 
+struct Input {
+  bool assigned;
+  std::string source;
+  std::vector<unsigned> location;  // "Directions" to the relevant scope.
+};
+
+static void TestMaybeAssigned(i::Zone* zone, Input input, const char* variable,
+                              bool module, bool allow_lazy_parsing) {
+  i::Factory* factory = CcTest::i_isolate()->factory();
+  i::Handle<i::String> string =
+      factory->InternalizeUtf8String(input.source.c_str());
+  string->PrintOn(stdout);
+  printf("\n");
+  i::Handle<i::Script> script = factory->NewScript(string);
+
+  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_parsing);
+
+  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());
+
+  i::Variable* var;
+  {
+    // Find the variable.
+    for (auto it = input.location.begin(); it != input.location.end(); ++it) {
+      unsigned n = *it;
+      scope = scope->inner_scope();
+      while (n-- > 0) {
+        scope = scope->sibling();
+      }
+    }
+    CHECK_NOT_NULL(scope);
+    const i::AstRawString* var_name =
+        info->ast_value_factory()->GetOneByteString(variable);
+    var = scope->Lookup(var_name);
+  }
+
+  CHECK(var->is_used());
+  STATIC_ASSERT(true == i::kMaybeAssigned);
+  CHECK_EQ(input.assigned, var->maybe_assigned() == i::kMaybeAssigned);
+}
+
+static Input wrap(Input input) {
+  Input result;
+  result.assigned = input.assigned;
+  result.source = "function WRAPPED() { " + input.source + " }";
+  result.location.push_back(0);
+  for (auto n : input.location) {
+    result.location.push_back(n);
+  }
+  return result;
+}
+
+TEST(MaybeAssignedInsideLoop) {
+  i::Isolate* isolate = CcTest::i_isolate();
+  i::HandleScope scope(isolate);
+  LocalContext env;
+  i::Zone zone(isolate->allocator(), ZONE_NAME);
+
+  std::vector<unsigned> top;  // Can't use {} in initializers below.
+
+  Input module_and_script_tests[] = {
+      {1, "for (j=x; j<10; ++j) { foo = j }", top},
+      {1, "for (j=x; j<10; ++j) { [foo] = [j] }", top},
+      {1, "for (j=x; j<10; ++j) { var foo = j }", top},
+      {1, "for (j=x; j<10; ++j) { var [foo] = [j] }", top},
+      {0, "for (j=x; j<10; ++j) { let foo = j }", {0}},
+      {0, "for (j=x; j<10; ++j) { let [foo] = [j] }", {0}},
+      {0, "for (j=x; j<10; ++j) { const foo = j }", {0}},
+      {0, "for (j=x; j<10; ++j) { const [foo] = [j] }", {0}},
+      {0, "for (j=x; j<10; ++j) { function foo() {return j} }", {0}},
+
+      {1, "for ({j}=x; j<10; ++j) { foo = j }", top},
+      {1, "for ({j}=x; j<10; ++j) { [foo] = [j] }", top},
+      {1, "for ({j}=x; j<10; ++j) { var foo = j }", top},
+      {1, "for ({j}=x; j<10; ++j) { var [foo] = [j] }", top},
+      {0, "for ({j}=x; j<10; ++j) { let foo = j }", {0}},
+      {0, "for ({j}=x; j<10; ++j) { let [foo] = [j] }", {0}},
+      {0, "for ({j}=x; j<10; ++j) { const foo = j }", {0}},
+      {0, "for ({j}=x; j<10; ++j) { const [foo] = [j] }", {0}},
+      {0, "for ({j}=x; j<10; ++j) { function foo() {return j} }", {0}},
+
+      {1, "for (var j=x; j<10; ++j) { foo = j }", top},
+      {1, "for (var j=x; j<10; ++j) { [foo] = [j] }", top},
+      {1, "for (var j=x; j<10; ++j) { var foo = j }", top},
+      {1, "for (var j=x; j<10; ++j) { var [foo] = [j] }", top},
+      {0, "for (var j=x; j<10; ++j) { let foo = j }", {0}},
+      {0, "for (var j=x; j<10; ++j) { let [foo] = [j] }", {0}},
+      {0, "for (var j=x; j<10; ++j) { const foo = j }", {0}},
+      {0, "for (var j=x; j<10; ++j) { const [foo] = [j] }", {0}},
+      {0, "for (var j=x; j<10; ++j) { function foo() {return j} }", {0}},
+
+      {1, "for (var {j}=x; j<10; ++j) { foo = j }", top},
+      {1, "for (var {j}=x; j<10; ++j) { [foo] = [j] }", top},
+      {1, "for (var {j}=x; j<10; ++j) { var foo = j }", top},
+      {1, "for (var {j}=x; j<10; ++j) { var [foo] = [j] }", top},
+      {0, "for (var {j}=x; j<10; ++j) { let foo = j }", {0}},
+      {0, "for (var {j}=x; j<10; ++j) { let [foo] = [j] }", {0}},
+      {0, "for (var {j}=x; j<10; ++j) { const foo = j }", {0}},
+      {0, "for (var {j}=x; j<10; ++j) { const [foo] = [j] }", {0}},
+      {0, "for (var {j}=x; j<10; ++j) { function foo() {return j} }", {0}},
+
+      {1, "for (let j=x; j<10; ++j) { foo = j }", top},
+      {1, "for (let j=x; j<10; ++j) { [foo] = [j] }", top},
+      {1, "for (let j=x; j<10; ++j) { var foo = j }", top},
+      {1, "for (let j=x; j<10; ++j) { var [foo] = [j] }", top},
+      {0, "for (let j=x; j<10; ++j) { let foo = j }", {0, 0, 0}},
+      {0, "for (let j=x; j<10; ++j) { let [foo] = [j] }", {0, 0, 0}},
+      {0, "for (let j=x; j<10; ++j) { const foo = j }", {0, 0, 0}},
+      {0, "for (let j=x; j<10; ++j) { const [foo] = [j] }", {0, 0, 0}},
+      {0, "for (let j=x; j<10; ++j) { function foo() {return j} }", {0, 0, 0}},
+
+      {1, "for (let {j}=x; j<10; ++j) { foo = j }", top},
+      {1, "for (let {j}=x; j<10; ++j) { [foo] = [j] }", top},
+      {1, "for (let {j}=x; j<10; ++j) { var foo = j }", top},
+      {1, "for (let {j}=x; j<10; ++j) { var [foo] = [j] }", top},
+      {0, "for (let {j}=x; j<10; ++j) { let foo = j }", {0, 0, 0}},
+      {0, "for (let {j}=x; j<10; ++j) { let [foo] = [j] }", {0, 0, 0}},
+      {0, "for (let {j}=x; j<10; ++j) { const foo = j }", {0, 0, 0}},
+      {0, "for (let {j}=x; j<10; ++j) { const [foo] = [j] }", {0, 0, 0}},
+      {0, "for (let {j}=x; j<10; ++j) { function foo(){return j} }", {0, 0, 0}},
+
+      {1, "for (j of x) { foo = j }", top},
+      {1, "for (j of x) { [foo] = [j] }", top},
+      {1, "for (j of x) { var foo = j }", top},
+      {1, "for (j of x) { var [foo] = [j] }", top},
+      {0, "for (j of x) { let foo = j }", {0}},
+      {0, "for (j of x) { let [foo] = [j] }", {0}},
+      {0, "for (j of x) { const foo = j }", {0}},
+      {0, "for (j of x) { const [foo] = [j] }", {0}},
+      {0, "for (j of x) { function foo() {return j} }", {0}},
+
+      {1, "for ({j} of x) { foo = j }", top},
+      {1, "for ({j} of x) { [foo] = [j] }", top},
+      {1, "for ({j} of x) { var foo = j }", top},
+      {1, "for ({j} of x) { var [foo] = [j] }", top},
+      {0, "for ({j} of x) { let foo = j }", {0}},
+      {0, "for ({j} of x) { let [foo] = [j] }", {0}},
+      {0, "for ({j} of x) { const foo = j }", {0}},
+      {0, "for ({j} of x) { const [foo] = [j] }", {0}},
+      {0, "for ({j} of x) { function foo() {return j} }", {0}},
+
+      {1, "for (var j of x) { foo = j }", top},
+      {1, "for (var j of x) { [foo] = [j] }", top},
+      {1, "for (var j of x) { var foo = j }", top},
+      {1, "for (var j of x) { var [foo] = [j] }", top},
+      {0, "for (var j of x) { let foo = j }", {0}},
+      {0, "for (var j of x) { let [foo] = [j] }", {0}},
+      {0, "for (var j of x) { const foo = j }", {0}},
+      {0, "for (var j of x) { const [foo] = [j] }", {0}},
+      {0, "for (var j of x) { function foo() {return j} }", {0}},
+
+      {1, "for (var {j} of x) { foo = j }", top},
+      {1, "for (var {j} of x) { [foo] = [j] }", top},
+      {1, "for (var {j} of x) { var foo = j }", top},
+      {1, "for (var {j} of x) { var [foo] = [j] }", top},
+      {0, "for (var {j} of x) { let foo = j }", {0}},
+      {0, "for (var {j} of x) { let [foo] = [j] }", {0}},
+      {0, "for (var {j} of x) { const foo = j }", {0}},
+      {0, "for (var {j} of x) { const [foo] = [j] }", {0}},
+      {0, "for (var {j} of x) { function foo() {return j} }", {0}},
+
+      {1, "for (let j of x) { foo = j }", top},
+      {1, "for (let j of x) { [foo] = [j] }", top},
+      {1, "for (let j of x) { var foo = j }", top},
+      {1, "for (let j of x) { var [foo] = [j] }", top},
+      {0, "for (let j of x) { let foo = j }", {0, 2, 0}},
+      {0, "for (let j of x) { let [foo] = [j] }", {0, 2, 0}},
+      {0, "for (let j of x) { const foo = j }", {0, 2, 0}},
+      {0, "for (let j of x) { const [foo] = [j] }", {0, 2, 0}},
+      {0, "for (let j of x) { function foo() {return j} }", {0, 2, 0}},
+
+      {1, "for (let {j} of x) { foo = j }", top},
+      {1, "for (let {j} of x) { [foo] = [j] }", top},
+      {1, "for (let {j} of x) { var foo = j }", top},
+      {1, "for (let {j} of x) { var [foo] = [j] }", top},
+      {0, "for (let {j} of x) { let foo = j }", {0, 2, 0}},
+      {0, "for (let {j} of x) { let [foo] = [j] }", {0, 2, 0}},
+      {0, "for (let {j} of x) { const foo = j }", {0, 2, 0}},
+      {0, "for (let {j} of x) { const [foo] = [j] }", {0, 2, 0}},
+      {0, "for (let {j} of x) { function foo() {return j} }", {0, 2, 0}},
+
+      {1, "for (const j of x) { foo = j }", top},
+      {1, "for (const j of x) { [foo] = [j] }", top},
+      {1, "for (const j of x) { var foo = j }", top},
+      {1, "for (const j of x) { var [foo] = [j] }", top},
+      {0, "for (const j of x) { let foo = j }", {0, 2, 0}},
+      {0, "for (const j of x) { let [foo] = [j] }", {0, 2, 0}},
+      {0, "for (const j of x) { const foo = j }", {0, 2, 0}},
+      {0, "for (const j of x) { const [foo] = [j] }", {0, 2, 0}},
+      {0, "for (const j of x) { function foo() {return j} }", {0, 2, 0}},
+
+      {1, "for (const {j} of x) { foo = j }", top},
+      {1, "for (const {j} of x) { [foo] = [j] }", top},
+      {1, "for (const {j} of x) { var foo = j }", top},
+      {1, "for (const {j} of x) { var [foo] = [j] }", top},
+      {0, "for (const {j} of x) { let foo = j }", {0, 2, 0}},
+      {0, "for (const {j} of x) { let [foo] = [j] }", {0, 2, 0}},
+      {0, "for (const {j} of x) { const foo = j }", {0, 2, 0}},
+      {0, "for (const {j} of x) { const [foo] = [j] }", {0, 2, 0}},
+      {0, "for (const {j} of x) { function foo() {return j} }", {0, 2, 0}},
+
+      {1, "for (j in x) { foo = j }", top},
+      {1, "for (j in x) { [foo] = [j] }", top},
+      {1, "for (j in x) { var foo = j }", top},
+      {1, "for (j in x) { var [foo] = [j] }", top},
+      {0, "for (j in x) { let foo = j }", {0}},
+      {0, "for (j in x) { let [foo] = [j] }", {0}},
+      {0, "for (j in x) { const foo = j }", {0}},
+      {0, "for (j in x) { const [foo] = [j] }", {0}},
+      {0, "for (j in x) { function foo() {return j} }", {0}},
+
+      {1, "for ({j} in x) { foo = j }", top},
+      {1, "for ({j} in x) { [foo] = [j] }", top},
+      {1, "for ({j} in x) { var foo = j }", top},
+      {1, "for ({j} in x) { var [foo] = [j] }", top},
+      {0, "for ({j} in x) { let foo = j }", {0}},
+      {0, "for ({j} in x) { let [foo] = [j] }", {0}},
+      {0, "for ({j} in x) { const foo = j }", {0}},
+      {0, "for ({j} in x) { const [foo] = [j] }", {0}},
+      {0, "for ({j} in x) { function foo() {return j} }", {0}},
+
+      {1, "for (var j in x) { foo = j }", top},
+      {1, "for (var j in x) { [foo] = [j] }", top},
+      {1, "for (var j in x) { var foo = j }", top},
+      {1, "for (var j in x) { var [foo] = [j] }", top},
+      {0, "for (var j in x) { let foo = j }", {0}},
+      {0, "for (var j in x) { let [foo] = [j] }", {0}},
+      {0, "for (var j in x) { const foo = j }", {0}},
+      {0, "for (var j in x) { const [foo] = [j] }", {0}},
+      {0, "for (var j in x) { function foo() {return j} }", {0}},
+
+      {1, "for (var {j} in x) { foo = j }", top},
+      {1, "for (var {j} in x) { [foo] = [j] }", top},
+      {1, "for (var {j} in x) { var foo = j }", top},
+      {1, "for (var {j} in x) { var [foo] = [j] }", top},
+      {0, "for (var {j} in x) { let foo = j }", {0}},
+      {0, "for (var {j} in x) { let [foo] = [j] }", {0}},
+      {0, "for (var {j} in x) { const foo = j }", {0}},
+      {0, "for (var {j} in x) { const [foo] = [j] }", {0}},
+      {0, "for (var {j} in x) { function foo() {return j} }", {0}},
+
+      {1, "for (let j in x) { foo = j }", top},
+      {1, "for (let j in x) { [foo] = [j] }", top},
+      {1, "for (let j in x) { var foo = j }", top},
+      {1, "for (let j in x) { var [foo] = [j] }", top},
+      {0, "for (let j in x) { let foo = j }", {0, 0, 0}},
+      {0, "for (let j in x) { let [foo] = [j] }", {0, 0, 0}},
+      {0, "for (let j in x) { const foo = j }", {0, 0, 0}},
+      {0, "for (let j in x) { const [foo] = [j] }", {0, 0, 0}},
+      {0, "for (let j in x) { function foo() {return j} }", {0, 0, 0}},
+
+      {1, "for (let {j} in x) { foo = j }", top},
+      {1, "for (let {j} in x) { [foo] = [j] }", top},
+      {1, "for (let {j} in x) { var foo = j }", top},
+      {1, "for (let {j} in x) { var [foo] = [j] }", top},
+      {0, "for (let {j} in x) { let foo = j }", {0, 0, 0}},
+      {0, "for (let {j} in x) { let [foo] = [j] }", {0, 0, 0}},
+      {0, "for (let {j} in x) { const foo = j }", {0, 0, 0}},
+      {0, "for (let {j} in x) { const [foo] = [j] }", {0, 0, 0}},
+      {0, "for (let {j} in x) { function foo() {return j} }", {0, 0, 0}},
+
+      {1, "for (const j in x) { foo = j }", top},
+      {1, "for (const j in x) { [foo] = [j] }", top},
+      {1, "for (const j in x) { var foo = j }", top},
+      {1, "for (const j in x) { var [foo] = [j] }", top},
+      {0, "for (const j in x) { let foo = j }", {0, 0, 0}},
+      {0, "for (const j in x) { let [foo] = [j] }", {0, 0, 0}},
+      {0, "for (const j in x) { const foo = j }", {0, 0, 0}},
+      {0, "for (const j in x) { const [foo] = [j] }", {0, 0, 0}},
+      {0, "for (const j in x) { function foo() {return j} }", {0, 0, 0}},
+
+      {1, "for (const {j} in x) { foo = j }", top},
+      {1, "for (const {j} in x) { [foo] = [j] }", top},
+      {1, "for (const {j} in x) { var foo = j }", top},
+      {1, "for (const {j} in x) { var [foo] = [j] }", top},
+      {0, "for (const {j} in x) { let foo = j }", {0, 0, 0}},
+      {0, "for (const {j} in x) { let [foo] = [j] }", {0, 0, 0}},
+      {0, "for (const {j} in x) { const foo = j }", {0, 0, 0}},
+      {0, "for (const {j} in x) { const [foo] = [j] }", {0, 0, 0}},
+      {0, "for (const {j} in x) { function foo() {return j} }", {0, 0, 0}},
+
+      {1, "while (j) { foo = j }", top},
+      {1, "while (j) { [foo] = [j] }", top},
+      {1, "while (j) { var foo = j }", top},
+      {1, "while (j) { var [foo] = [j] }", top},
+      {0, "while (j) { let foo = j }", {0}},
+      {0, "while (j) { let [foo] = [j] }", {0}},
+      {0, "while (j) { const foo = j }", {0}},
+      {0, "while (j) { const [foo] = [j] }", {0}},
+      {0, "while (j) { function foo() {return j} }", {0}},
+
+      {1, "do { foo = j } while (j)", top},
+      {1, "do { [foo] = [j] } while (j)", top},
+      {1, "do { var foo = j } while (j)", top},
+      {1, "do { var [foo] = [j] } while (j)", top},
+      {0, "do { let foo = j } while (j)", {0}},
+      {0, "do { let [foo] = [j] } while (j)", {0}},
+      {0, "do { const foo = j } while (j)", {0}},
+      {0, "do { const [foo] = [j] } while (j)", {0}},
+      {0, "do { function foo() {return j} } while (j)", {0}},
+  };
+
+  Input script_only_tests[] = {
+      {1, "for (j=x; j<10; ++j) { function foo() {return j} }", top},
+      {1, "for ({j}=x; j<10; ++j) { function foo() {return j} }", top},
+      {1, "for (var j=x; j<10; ++j) { function foo() {return j} }", top},
+      {1, "for (var {j}=x; j<10; ++j) { function foo() {return j} }", top},
+      {1, "for (let j=x; j<10; ++j) { function foo() {return j} }", top},
+      {1, "for (let {j}=x; j<10; ++j) { function foo() {return j} }", top},
+      {1, "for (j of x) { function foo() {return j} }", top},
+      {1, "for ({j} of x) { function foo() {return j} }", top},
+      {1, "for (var j of x) { function foo() {return j} }", top},
+      {1, "for (var {j} of x) { function foo() {return j} }", top},
+      {1, "for (let j of x) { function foo() {return j} }", top},
+      {1, "for (let {j} of x) { function foo() {return j} }", top},
+      {1, "for (const j of x) { function foo() {return j} }", top},
+      {1, "for (const {j} of x) { function foo() {return j} }", top},
+      {1, "for (j in x) { function foo() {return j} }", top},
+      {1, "for ({j} in x) { function foo() {return j} }", top},
+      {1, "for (var j in x) { function foo() {return j} }", top},
+      {1, "for (var {j} in x) { function foo() {return j} }", top},
+      {1, "for (let j in x) { function foo() {return j} }", top},
+      {1, "for (let {j} in x) { function foo() {return j} }", top},
+      {1, "for (const j in x) { function foo() {return j} }", top},
+      {1, "for (const {j} in x) { function foo() {return j} }", top},
+      {1, "while (j) { function foo() {return j} }", top},
+      {1, "do { function foo() {return j} } while (j)", top},
+  };
+
+  for (unsigned i = 0; i < arraysize(module_and_script_tests); ++i) {
+    Input input = module_and_script_tests[i];
+    for (unsigned module = 0; module <= 1; ++module) {
+      for (unsigned allow_lazy_parsing = 0; allow_lazy_parsing <= 1;
+           ++allow_lazy_parsing) {
+        TestMaybeAssigned(&zone, input, "foo", module, allow_lazy_parsing);
+      }
+      TestMaybeAssigned(&zone, wrap(input), "foo", module, false);
+    }
+  }
+
+  for (unsigned i = 0; i < arraysize(script_only_tests); ++i) {
+    Input input = script_only_tests[i];
+    for (unsigned allow_lazy_parsing = 0; allow_lazy_parsing <= 1;
+         ++allow_lazy_parsing) {
+      TestMaybeAssigned(&zone, input, "foo", false, allow_lazy_parsing);
+    }
+    TestMaybeAssigned(&zone, wrap(input), "foo", false, false);
+  }
+}
+
 TEST(MaybeAssignedTopLevel) {
   i::Isolate* isolate = CcTest::i_isolate();
   i::HandleScope scope(isolate);

test/mjsunit/regress/regress-5636-1.js

+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --allow-natives-syntax --function-context-specialization
+
+function f(n) {
+  var a = [];
+  function g() { return x }
+  for (var i = 0; i < n; ++i) {
+    var x = i;
+    a[i] = g;
+    %OptimizeFunctionOnNextCall(g);
+    g();
+  }
+  return a;
+}
+var a = f(3);
+assertEquals(3, a.length);
+assertEquals(2, a[0]());
+assertEquals(2, a[1]());
+assertEquals(2, a[2]());

test/mjsunit/regress/regress-5636-2.js

+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --allow-natives-syntax
+
+function f(n) {
+  "use asm";
+  var a = [];
+  function g() { return x }
+  for (var i = 0; i < n; ++i) {
+    var x = i;
+    a[i] = g;
+    %OptimizeFunctionOnNextCall(g);
+    g();
+  }
+  return a;
+}
+var a = f(3);
+assertEquals(3, a.length);
+assertEquals(2, a[0]());
+assertEquals(2, a[1]());
+assertEquals(2, a[2]());