[parser] Skipping inner funcs: produce correct data for var redeclarations.

This unifies the behavior of Scope::DeclareVariableName with
Scope::DeclareVariable.

BUG=v8:5516

Review-Url: https://codereview.chromium.org/2658063005
Cr-Commit-Position: refs/heads/master@{#42744}

src/ast/scopes.cc

@@ -1083,8 +1083,14 @@ void Scope::DeclareVariableName(const AstRawString* name, VariableMode mode) {
   // Declare the variable in the declaration scope.
   if (FLAG_preparser_scope_analysis) {
     Variable* var = LookupLocal(name);
+    DCHECK_NE(var, kDummyPreParserLexicalVariable);
+    DCHECK_NE(var, kDummyPreParserVariable);
     if (var == nullptr) {
       var = DeclareLocal(name, mode);
+    } else if (!IsLexicalVariableMode(var->mode()) &&
+               !IsLexicalVariableMode(mode)) {
+      DCHECK_EQ(mode, VAR);
+      var->set_maybe_assigned();
     }
     var->set_is_used();
   } else {

test/cctest/test-parsing.cc

@@ -9066,6 +9066,15 @@ TEST(PreParserScopeAnalysis) {
       {"", "const var1 = 5;"},
       {"", "if (true) { const var1 = 5; }"},
       {"", "const var1 = 5; function f() { var1; }"},
+
+      {"", "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; }"},
   };
 
   for (unsigned i = 0; i < arraysize(inners); ++i) {