Split function block scoping into a separate flag

In an initial attempt to implement sloppy mode lexical bindings,
functions were made lexically scoped in sloppy mode. However, the
ES2015 spec says that they need an additional hoisted var binding,
and further, it's not clear when we'll implement that behavior
or whether it's web-compatible.

This patch splits off function block scoping into a new, separate
flag called --harmony_sloppy_function. This change will enable the
possibility of testing and shipping this feature separately from
other block scoping-related features which don't have the same risks.

BUG=v8:4285
R=adamk
LOG=N

Review URL: https://codereview.chromium.org/1282093002

Cr-Commit-Position: refs/heads/master@{#30122}

src/bootstrapper.cc

@@ -1840,6 +1840,7 @@ EMPTY_NATIVE_FUNCTIONS_FOR_FEATURE(harmony_regexps)
 EMPTY_NATIVE_FUNCTIONS_FOR_FEATURE(harmony_arrow_functions)
 EMPTY_NATIVE_FUNCTIONS_FOR_FEATURE(harmony_tostring)
 EMPTY_NATIVE_FUNCTIONS_FOR_FEATURE(harmony_sloppy)
+EMPTY_NATIVE_FUNCTIONS_FOR_FEATURE(harmony_sloppy_function)
 EMPTY_NATIVE_FUNCTIONS_FOR_FEATURE(harmony_sloppy_let)
 EMPTY_NATIVE_FUNCTIONS_FOR_FEATURE(harmony_unicode_regexps)
 EMPTY_NATIVE_FUNCTIONS_FOR_FEATURE(harmony_rest_parameters)
@@ -1876,6 +1877,7 @@ EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_array_includes)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_arrow_functions)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_proxies)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_sloppy)
+EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_sloppy_function)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_sloppy_let)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_rest_parameters)
 EMPTY_INITIALIZE_GLOBAL_FOR_FEATURE(harmony_spreadcalls)
@@ -2558,6 +2560,7 @@ bool Genesis::InstallExperimentalNatives() {
   static const char* harmony_tostring_natives[] = {"native harmony-tostring.js",
                                                    nullptr};
   static const char* harmony_sloppy_natives[] = {nullptr};
+  static const char* harmony_sloppy_function_natives[] = {nullptr};
   static const char* harmony_sloppy_let_natives[] = {nullptr};
   static const char* harmony_unicode_regexps_natives[] = {nullptr};
   static const char* harmony_rest_parameters_natives[] = {nullptr};

src/flag-definitions.h

@@ -190,6 +190,7 @@ DEFINE_BOOL(legacy_const, true, "legacy semantics for const in sloppy mode")
   V(harmony_regexps, "harmony regular expression extensions")         \
   V(harmony_proxies, "harmony proxies")                               \
   V(harmony_sloppy, "harmony features in sloppy mode")                \
+  V(harmony_sloppy_function, "harmony sloppy function block scoping") \
   V(harmony_sloppy_let, "harmony let in sloppy mode")                 \
   V(harmony_unicode_regexps, "harmony unicode regexps")               \
   V(harmony_reflect, "harmony Reflect API")                           \

src/parser.cc

@@ -912,6 +912,7 @@ Parser::Parser(ParseInfo* info)
   set_allow_natives(FLAG_allow_natives_syntax || info->is_native());
   set_allow_harmony_arrow_functions(FLAG_harmony_arrow_functions);
   set_allow_harmony_sloppy(FLAG_harmony_sloppy);
+  set_allow_harmony_sloppy_function(FLAG_harmony_sloppy_function);
   set_allow_harmony_sloppy_let(FLAG_harmony_sloppy_let);
   set_allow_harmony_rest_parameters(FLAG_harmony_rest_parameters);
   set_allow_harmony_spreadcalls(FLAG_harmony_spreadcalls);
@@ -2224,8 +2225,10 @@ Statement* Parser::ParseFunctionDeclaration(
   VariableMode mode =
       is_strong(language_mode())
           ? CONST
-          : (is_strict(language_mode()) || allow_harmony_sloppy()) &&
-              !scope_->is_declaration_scope() ? LET : VAR;
+          : (is_strict(language_mode()) || allow_harmony_sloppy_function()) &&
+                    !scope_->is_declaration_scope()
+                ? LET
+                : VAR;
   VariableProxy* proxy = NewUnresolved(name, mode);
   Declaration* declaration =
       factory()->NewFunctionDeclaration(proxy, mode, fun, scope_, pos);

src/preparser.h

@@ -108,6 +108,7 @@ class ParserBase : public Traits {
         allow_natives_(false),
         allow_harmony_arrow_functions_(false),
         allow_harmony_sloppy_(false),
+        allow_harmony_sloppy_function_(false),
         allow_harmony_sloppy_let_(false),
         allow_harmony_rest_parameters_(false),
         allow_harmony_spreadcalls_(false),
@@ -125,6 +126,7 @@ class ParserBase : public Traits {
   ALLOW_ACCESSORS(natives);
   ALLOW_ACCESSORS(harmony_arrow_functions);
   ALLOW_ACCESSORS(harmony_sloppy);
+  ALLOW_ACCESSORS(harmony_sloppy_function);
   ALLOW_ACCESSORS(harmony_sloppy_let);
   ALLOW_ACCESSORS(harmony_rest_parameters);
   ALLOW_ACCESSORS(harmony_spreadcalls);
@@ -798,6 +800,7 @@ class ParserBase : public Traits {
   bool allow_natives_;
   bool allow_harmony_arrow_functions_;
   bool allow_harmony_sloppy_;
+  bool allow_harmony_sloppy_function_;
   bool allow_harmony_sloppy_let_;
   bool allow_harmony_rest_parameters_;
   bool allow_harmony_spreadcalls_;

test/mjsunit/harmony/block-conflicts-sloppy.js

@@ -4,7 +4,7 @@
 
 // Test for conflicting variable bindings.
 
-// Flags: --no-legacy-const --harmony-sloppy --harmony-sloppy-let
+// Flags: --no-legacy-const --harmony-sloppy --harmony-sloppy-let --harmony-sloppy-function
 
 function CheckException(e) {
   var string = e.toString();

test/mjsunit/harmony/block-let-semantics-sloppy.js

@@ -25,7 +25,7 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-// Flags: --harmony-sloppy --no-legacy-const --harmony-sloppy-let
+// Flags: --harmony-sloppy --no-legacy-const --harmony-sloppy-let --harmony-sloppy-function
 
 // Test temporal dead zone semantics of let bound variables in
 // function and block scopes.

test/mjsunit/harmony/block-scope-class.js

@@ -4,7 +4,7 @@
 
 // Test for conflicting variable bindings.
 
-// Flags: --harmony-sloppy
+// Flags: --harmony-sloppy --harmony-sloppy-function
 
 function AssertEqualsStrictAndSloppy(value, code) {
   assertEquals(value, eval("(function() {" + code + "})()"));

test/mjsunit/harmony/block-scoping-sloppy.js

@@ -25,7 +25,7 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-// Flags: --allow-natives-syntax --harmony-sloppy --no-legacy-const --harmony-sloppy-let
+// Flags: --allow-natives-syntax --harmony-sloppy --no-legacy-const --harmony-sloppy-let --harmony-sloppy-function
 // Test functionality of block scopes.
 
 // Hoisting of var declarations.