[destructuring] Refactor duplicate parameter name detection.

src/expression-classifier.h

Index: src/expression-classifier.h
diff --git a/src/expression-classifier.h b/src/expression-classifier.h
new file mode 100644
index 0000000000000000000000000000000000000000..b9e36ab0b6adc5e4e0865d309eba78830a0006b9
--- /dev/null
+++ b/src/expression-classifier.h
@@ -0,0 +1,231 @@
+// Copyright 2015 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.
+
+#ifndef V8_EXPRESSION_CLASSIFIER_H
+#define V8_EXPRESSION_CLASSIFIER_H
+
+#include "src/v8.h"
+
+#include "src/messages.h"
+#include "src/scanner.h"
+#include "src/token.h"
+
+namespace v8 {
+namespace internal {
+
+
+class ExpressionClassifier {
+ public:
+  struct Error {
+    Error()
+        : location(Scanner::Location::invalid()),
+          message(MessageTemplate::kNone),
+          arg(nullptr) {}
+
+    Scanner::Location location;
+    MessageTemplate::Template message;
+    const char* arg;
+
+    bool HasError() const { return location.IsValid(); }
+  };
+
+  ExpressionClassifier() : duplicate_finder_(nullptr) {}
+
+  explicit ExpressionClassifier(DuplicateFinder* duplicate_finder)
+      : duplicate_finder_(duplicate_finder) {}
+
+  DuplicateFinder* duplicate_finder() const { return duplicate_finder_; }
+
+  bool is_valid_expression() const { return !expression_error_.HasError(); }
+
+  bool is_valid_binding_pattern() const {
+    return !binding_pattern_error_.HasError();
+  }
+
+  bool is_valid_assignment_pattern() const {
+    return !assignment_pattern_error_.HasError();
+  }
+
+  bool is_valid_arrow_formal_parameters() const {
+    return !arrow_formal_parameters_error_.HasError();
+  }
+
+  bool is_valid_formal_parameter_list_without_duplicates() const {
+    return !duplicate_formal_parameter_error_.HasError();
+  }
+
+  // Note: callers should also check
+  // is_valid_formal_parameter_list_without_duplicates().
+  bool is_valid_strict_mode_formal_parameters() const {
+    return !strict_mode_formal_parameter_error_.HasError();
+  }
+
+  // Note: callers should also check is_valid_strict_mode_formal_parameters()
+  // and is_valid_formal_parameter_list_without_duplicates().
+  bool is_valid_strong_mode_formal_parameters() const {
+    return !strong_mode_formal_parameter_error_.HasError();
+  }
+
+  const Error& expression_error() const { return expression_error_; }
+
+  const Error& binding_pattern_error() const { return binding_pattern_error_; }
+
+  const Error& assignment_pattern_error() const {
+    return assignment_pattern_error_;
+  }
+
+  const Error& arrow_formal_parameters_error() const {
+    return arrow_formal_parameters_error_;
+  }
+
+  const Error& duplicate_formal_parameter_error() const {
+    return duplicate_formal_parameter_error_;
+  }
+
+  const Error& strict_mode_formal_parameter_error() const {
+    return strict_mode_formal_parameter_error_;
+  }
+
+  const Error& strong_mode_formal_parameter_error() const {
+    return strong_mode_formal_parameter_error_;
+  }
+
+  void RecordExpressionError(const Scanner::Location& loc,
+                             MessageTemplate::Template message,
+                             const char* arg = nullptr) {
+    if (!is_valid_expression()) return;
+    expression_error_.location = loc;
+    expression_error_.message = message;
+    expression_error_.arg = arg;
+  }
+
+  void RecordBindingPatternError(const Scanner::Location& loc,
+                                 MessageTemplate::Template message,
+                                 const char* arg = nullptr) {
+    if (!is_valid_binding_pattern()) return;
+    binding_pattern_error_.location = loc;
+    binding_pattern_error_.message = message;
+    binding_pattern_error_.arg = arg;
+  }
+
+  void RecordAssignmentPatternError(const Scanner::Location& loc,
+                                    MessageTemplate::Template message,
+                                    const char* arg = nullptr) {
+    if (!is_valid_assignment_pattern()) return;
+    assignment_pattern_error_.location = loc;
+    assignment_pattern_error_.message = message;
+    assignment_pattern_error_.arg = arg;
+  }
+
+  void RecordArrowFormalParametersError(const Scanner::Location& loc,
+                                        MessageTemplate::Template message,
+                                        const char* arg = nullptr) {
+    if (!is_valid_arrow_formal_parameters()) return;
+    arrow_formal_parameters_error_.location = loc;
+    arrow_formal_parameters_error_.message = message;
+    arrow_formal_parameters_error_.arg = arg;
+  }
+
+  void RecordDuplicateFormalParameterError(const Scanner::Location& loc) {
+    if (!is_valid_formal_parameter_list_without_duplicates()) return;
+    duplicate_formal_parameter_error_.location = loc;
+    duplicate_formal_parameter_error_.message =
+        MessageTemplate::kStrictParamDupe;
+    duplicate_formal_parameter_error_.arg = nullptr;
+  }
+
+  // Record a binding that would be invalid in strict mode.  Confusingly this
+  // is not the same as StrictFormalParameterList, which simply forbids
+  // duplicate bindings.
+  void RecordStrictModeFormalParameterError(const Scanner::Location& loc,
+                                            MessageTemplate::Template message,
+                                            const char* arg = nullptr) {
+    if (!is_valid_strict_mode_formal_parameters()) return;
+    strict_mode_formal_parameter_error_.location = loc;
+    strict_mode_formal_parameter_error_.message = message;
+    strict_mode_formal_parameter_error_.arg = arg;
+  }
+
+  void RecordStrongModeFormalParameterError(const Scanner::Location& loc,
+                                            MessageTemplate::Template message,
+                                            const char* arg = nullptr) {
+    if (!is_valid_strong_mode_formal_parameters()) return;
+    strong_mode_formal_parameter_error_.location = loc;
+    strong_mode_formal_parameter_error_.message = message;
+    strong_mode_formal_parameter_error_.arg = arg;
+  }
+
+  enum TargetProduction {
+    ExpressionProduction = 1 << 0,
+    BindingPatternProduction = 1 << 1,
+    AssignmentPatternProduction = 1 << 2,
+    FormalParametersProduction = 1 << 3,
+    ArrowFormalParametersProduction = 1 << 4,
+    StandardProductions = (ExpressionProduction | BindingPatternProduction |
+                           AssignmentPatternProduction),
+    PatternProductions = BindingPatternProduction | AssignmentPatternProduction,
+    AllProductions = (StandardProductions | FormalParametersProduction |
+                      ArrowFormalParametersProduction),
+  };
+
+  void Accumulate(const ExpressionClassifier& inner,
+                  unsigned productions = StandardProductions) {
+    if (productions & ExpressionProduction && is_valid_expression()) {
+      expression_error_ = inner.expression_error_;
+    }
+    if (productions & BindingPatternProduction && is_valid_binding_pattern()) {
+      binding_pattern_error_ = inner.binding_pattern_error_;
+    }
+    if (productions & AssignmentPatternProduction &&
+        is_valid_assignment_pattern()) {
+      assignment_pattern_error_ = inner.assignment_pattern_error_;
+    }
+    if (productions & FormalParametersProduction) {
+      if (is_valid_formal_parameter_list_without_duplicates()) {
+        duplicate_formal_parameter_error_ =
+            inner.duplicate_formal_parameter_error_;
+      }
+      if (is_valid_strict_mode_formal_parameters()) {
+        strict_mode_formal_parameter_error_ =
+            inner.strict_mode_formal_parameter_error_;
+      }
+      if (is_valid_strong_mode_formal_parameters()) {
+        strong_mode_formal_parameter_error_ =
+            inner.strong_mode_formal_parameter_error_;
+      }
+    }
+    if (productions & ArrowFormalParametersProduction &&
+        is_valid_arrow_formal_parameters()) {
+      // The result continues to be a valid arrow formal parameters if the
+      // inner expression is a valid binding pattern.
+      arrow_formal_parameters_error_ = inner.binding_pattern_error_;
+    }
+  }
+
+  void AccumulateReclassifyingAsPattern(const ExpressionClassifier& inner) {
+    Accumulate(inner, AllProductions & ~PatternProductions);
+    if (!inner.is_valid_expression()) {
+      if (is_valid_binding_pattern()) {
+        binding_pattern_error_ = inner.expression_error();
+      }
+      if (is_valid_assignment_pattern()) {
+        assignment_pattern_error_ = inner.expression_error();
+      }
+    }
+  }
+
+ private:
+  Error expression_error_;
+  Error binding_pattern_error_;
+  Error assignment_pattern_error_;
+  Error arrow_formal_parameters_error_;
+  Error duplicate_formal_parameter_error_;
+  Error strict_mode_formal_parameter_error_;
+  Error strong_mode_formal_parameter_error_;
+  DuplicateFinder* duplicate_finder_;
+};
+}
+}  // v8::internal
+
+#endif  // V8_EXPRESSION_CLASSIFIER_H