Remove frog from the repository.

frog/block_scope.dart

-// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-
-class BlockScope {
-  MethodGenerator enclosingMethod;
-  BlockScope parent;
-
-  // TODO(jimhug): Using a list or tree-based map may improve perf; the list
-  // is normally small.
-  CopyOnWriteMap<String, VariableValue> _vars;
-
-  /** Used JS names, if different from the Dart name. */
-  Set<String> _jsNames;
-
-  /**
-   * Variables in this method that have been captured by lambdas.
-   * Don't reuse the names in child blocks.
-   */
-  Set<String> _closedOver;
-
-  /** If we are in a catch block, this is the exception variable to rethrow. */
-  String rethrow;
-
-  /**
-   * True if the block is reentrant while the current method is executing.
-   * This is only used for the blocks within loops.
-   */
-  bool reentrant;
-
-  /** Tracks the node that this scope is associated with, for debugging */
-  Node node;
-
-  /** True if we should try to infer types for this block. */
-  bool inferTypes;
-
-  BlockScope(this.enclosingMethod, this.parent, this.node,
-      [bool reentrant = false])
-    : this.reentrant = reentrant,
-      _vars = new CopyOnWriteMap<String, VariableValue>(),
-      _jsNames = new Set<String>() {
-
-    if (isMethodScope) {
-      _closedOver = new Set<String>();
-    } else {
-      // Blocks within a reentrant block are also reentrant.
-      this.reentrant = reentrant || parent.reentrant;
-    }
-    inferTypes = options.inferTypes && (parent == null || parent.inferTypes);
-  }
-
-  /** See the [snapshot] method for a description. */
-  BlockScope._snapshot(BlockScope original)
-    : enclosingMethod = original.enclosingMethod,
-      parent = original.parent == null ? null : original.parent.snapshot(),
-      _vars = original._vars.clone(),
-      node = original.node,
-      inferTypes = original.inferTypes,
-      rethrow = original.rethrow,
-      // TODO(jmesserly): are these this right?
-      _jsNames = original._jsNames,
-      _closedOver = original._closedOver;
-
-  /** True if this is the top level scope of the method. */
-  bool get isMethodScope() {
-    return parent == null || parent.enclosingMethod != enclosingMethod;
-  }
-
-  /**
-   * Gets the method scope associated with this block scope (possibly itself).
-   */
-  BlockScope get methodScope() {
-    var s = this;
-    while (!s.isMethodScope) s = s.parent;
-    return s;
-  }
-
-  VariableValue lookup(String name) {
-    for (var s = this; s != null; s = s.parent) {
-      VariableValue ret = s._vars[name];
-      if (ret != null) return _capture(s, ret);
-    }
-    return null;
-  }
-
-  void inferAssign(String name, Value value) {
-    if (inferTypes) assign(name, value);
-  }
-
-  void assign(String name, Value value) {
-    for (var s = this; s != null; s = s.parent) {
-      var existing = s._vars[name];
-      if (existing != null) {
-        s._vars[name] = existing.replaceValue(value);
-        return;
-      }
-    }
-    world.internalError("assigning variable '${name}' that doesn't exist.");
-  }
-
-  Value _capture(BlockScope other, Value value) {
-    // If this variable is from a different method, it means we closed over
-    // it in the child lambda. Time for some bookeeping!
-    if (other.enclosingMethod != enclosingMethod) {
-      // Make sure the parent method doesn't reuse this variable to mean
-      // something else.
-      other.methodScope._closedOver.add(value.code);
-
-      // If the scope we found this variable in is reentrant, remember the
-      // variable. The lambda we're in will capture it with Function.bind.
-      if (enclosingMethod.captures != null && other.reentrant) {
-        enclosingMethod.captures.add(value.code);
-      }
-    }
-    return value;
-  }
-
-  /**
-   * Returns true if we can't use this name because we would be shadowing
-   * another name in the JS that we might need to access later.
-   */
-  bool _isDefinedInParent(String name) {
-    if (isMethodScope && _closedOver.contains(name)) return true;
-
-    for (var s = parent; s != null; s = s.parent) {
-      if (s._vars.containsKey(name)) return true;
-      if (s._jsNames.contains(name)) return true;
-      // Don't reuse a name that's been closed over
-      if (s.isMethodScope && s._closedOver.contains(name)) return true;
-    }
-
-    // Ensure that we don't shadow another name that would've been accessible,
-    // like top level names.
-    // (This lookup might report errors, which is a bit strange.
-    // But probably harmless since we have to pay for the lookup anyway.)
-    // TODO(jmesserly): does this work right if JS name of the top-level thing
-    // is different from Dart name?
-    final type = enclosingMethod.method.declaringType;
-    if (type.library.lookup(name, null) != null) return true;
-
-    // Nobody else needs this name. It's safe to reuse.
-    return false;
-  }
-
-
-  VariableValue create(String name, Type type, SourceSpan span,
-      [bool isFinal = false, bool isParameter = false]) {
-
-    var jsName = world.toJsIdentifier(name);
-    if (_vars.containsKey(name)) {
-      world.error('duplicate name "$name"', span);
-    }
-
-    // Make sure variables don't shadow any names we might need to access.
-    if (!isParameter) {
-      int index = 0;
-      while (_isDefinedInParent(jsName)) {
-        jsName = '$name${index++}';
-      }
-    }
-
-    var ret = new VariableValue(type, jsName, span, isFinal);
-    _vars[name] = ret;
-    if (name != jsName) _jsNames.add(jsName);
-    return ret;
-  }
-
-  Value declareParameter(Parameter p) {
-    return create(p.name, p.type, p.definition.span, isParameter:true);
-  }
-
-  /** Declares a variable in the current scope for this identifier. */
-  Value declare(DeclaredIdentifier id) {
-    var type = enclosingMethod.method.resolveType(id.type, false, true);
-    return create(id.name.name, type, id.span);
-  }
-
-  /**
-   * Finds the first lexically enclosing catch block, if any, and returns its
-   * exception variable.
-   */
-  String getRethrow() {
-    var scope = this;
-    while (scope.rethrow == null && scope.parent != null) {
-      scope = scope.parent;
-    }
-    return scope.rethrow;
-  }
-
-  /**
-   * Creates a snapshot of an existing BlockScope. Both the original and the
-   * returned copy are writable. Clones all the way to the root node.
-   */
-  // TODO(jmesserly): this might need to be optimized.
-  BlockScope snapshot() => new BlockScope._snapshot(this);
-
-  /**
-   * Unifies variable values with the ones in [other]. Returns `true` if
-   * anything changed, `false` otherwise.
-   */
-  bool unionWith(BlockScope other) {
-    bool changed = false;
-    if (parent != null) {
-      changed = parent.unionWith(other.parent);
-    }
-
-    // Optimization: check if the copy-on-write maps are the same
-    if (_vars._map !== other._vars._map) {
-      other._vars.forEach((String key, VariableValue otherVar) {
-        VariableValue myVar = _vars[key];
-        Value v = Value.union(myVar.value, otherVar.value);
-        if (myVar.value !== v) {
-          _vars[key] = myVar.replaceValue(v);
-          changed = true;
-        }
-      });
-    }
-
-    return changed;
-  }
-}