Revert "[parser] Fix variable caching for conflict lookup"

This reverts commit 026a0c21.

Reason for revert: Reverting due to https://crbug.com/1029461

Original change's description:
> [parser] Fix variable caching for conflict lookup
> 
> During conflict lookup (for lexical variables and sloppy block function
> hoisting), we cache the looked-up variable on the current scope if the
> lookup goes through a ScopeInfo. However, for variable lookup during
> scope analysis, we use the "entry point" as the cache.
> 
> Since both lookups can create Variables, this can cause us to create
> duplicate variables, e.g. a duplicate function name variable in the
> attached test.
> 
> Instead, for ScopeInfo conflict lookups we can cache the result on the
> function's outer scope, which shoud be equivalent to the entry point.
> 
> As a (necessary) drive-by, we can terminate the lookup early if we find
> a VAR with the same name, as we can safely assume that its existence
> means that it doesn't conflict, which means that our variable can't
> conflict either.
> 
> Bug: chromium:1026603
> Change-Id: I19f80f65597ba6573ebe0b48aa5698f55e5c3ea1
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1928861
> Commit-Queue: Leszek Swirski <leszeks@chromium.org>
> Reviewed-by: Toon Verwaest <verwaest@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#65138}

TBR=leszeks@chromium.org,verwaest@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: chromium:1026603
Bug: chromium:1029461
Change-Id: Id7f5dd342e32e1bb57c51b3748feff32ee0ba41d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1958014Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65390}

src/ast/scopes.cc

@@ -509,9 +509,9 @@ void DeclarationScope::HoistSloppyBlockFunctions(AstNodeFactory* factory) {
     // example, that does not prevent hoisting of the function in
     // `{ let e; try {} catch (e) { function e(){} } }`
     do {
-      var = query_scope->LookupInScopeOrScopeInfo(name, outer_scope_);
-      if (var != nullptr) {
-        should_hoist = !IsLexicalVariableMode(var->mode());
+      var = query_scope->LookupInScopeOrScopeInfo(name);
+      if (var != nullptr && IsLexicalVariableMode(var->mode())) {
+        should_hoist = false;
         break;
       }
       query_scope = query_scope->outer_scope();
@@ -1161,12 +1161,9 @@ Declaration* DeclarationScope::CheckConflictingVarDeclarations() {
     do {
       // There is a conflict if there exists a non-VAR binding up to the
       // declaration scope in which this sloppy-eval runs.
-      Variable* other_var = current->LookupInScopeOrScopeInfo(
-          decl->var()->raw_name(), outer_scope_);
-      if (other_var != nullptr) {
-        // If this is a VAR, then we know that it doesn't conflict with
-        // anything, so we can't conflict with anything either.
-        if (!IsLexicalVariableMode(other_var->mode())) return nullptr;
+      Variable* other_var =
+          current->LookupInScopeOrScopeInfo(decl->var()->raw_name());
+      if (other_var != nullptr && IsLexicalVariableMode(other_var->mode())) {
         DCHECK(!current->is_catch_scope());
         return decl;
       }

src/ast/scopes.h

@@ -558,16 +558,15 @@ class V8_EXPORT_PRIVATE Scope : public NON_EXPORTED_BASE(ZoneObject) {
     return false;
   }
 
-  Variable* LookupInScopeOrScopeInfo(const AstRawString* name, Scope* cache) {
+  Variable* LookupInScopeOrScopeInfo(const AstRawString* name) {
     Variable* var = variables_.Lookup(name);
     if (var != nullptr || scope_info_.is_null()) return var;
-    DCHECK_NOT_NULL(cache);
-    return LookupInScopeInfo(name, cache);
+    return LookupInScopeInfo(name, this);
   }
 
   Variable* LookupForTesting(const AstRawString* name) {
     for (Scope* scope = this; scope != nullptr; scope = scope->outer_scope()) {
-      Variable* var = scope->LookupInScopeOrScopeInfo(name, this);
+      Variable* var = scope->LookupInScopeOrScopeInfo(name);
       if (var != nullptr) return var;
     }
     return nullptr;

test/mjsunit/regress/regress-crbug-1026603.js

-// Copyright 2019 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.
-
-(function f() {
-  with ({}) {
-    // Make sure that variable conflict resulution and variable lookup through
-    // deserialized scopes use the same cache scope. Declare a variable which
-    // checks for (and fails to find) a conflict, allocating the f variable as
-    // it goes, then access f, which also looks up f.
-    eval("var f; f;");
-  }
-})();