com.google.dart.compiler.backend.js.ast.JsScope Maven / Gradle / Ivy
// Copyright (c) 2011, 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.
package com.google.dart.compiler.backend.js.ast;
import com.google.dart.compiler.util.Maps;
import org.jetbrains.annotations.NotNull;
import org.jetbrains.annotations.Nullable;
import java.util.Collections;
import java.util.HashMap;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import static com.google.dart.compiler.backend.js.ast.JsScopesKt.JsObjectScope;
/**
* A scope is a factory for creating and allocating
* {@link JsName}s. A JavaScript AST is
* built in terms of abstract name objects without worrying about obfuscation,
* keyword/identifier blacklisting, and so on.
*
*
*
* Scopes are associated with
* {@link JsFunction}s, but the two are
* not equivalent. Functions have scopes, but a scope does not
* necessarily have an associated Function. Examples of this include the
* {@link JsRootScope} and synthetic
* scopes that might be created by a client.
*
*
*
* Scopes can have parents to provide constraints when allocating actual
* identifiers for names. Specifically, names in child scopes are chosen such
* that they do not conflict with names in their parent scopes. The ultimate
* parent is usually the global scope (see
* {@link JsProgram#getRootScope()}),
* but parentless scopes are useful for managing names that are always accessed
* with a qualifier and could therefore never be confused with the global scope
* hierarchy.
*/
public abstract class JsScope {
@NotNull
private final String description;
private Map names = Collections.emptyMap();
private final JsScope parent;
protected int tempIndex = 0;
private final String scopeId;
private static final Pattern FRESH_NAME_SUFFIX = Pattern.compile("[\\$_]\\d+$");
public JsScope(JsScope parent, @NotNull String description, @Nullable String scopeId) {
this.scopeId = scopeId;
this.description = description;
this.parent = parent;
}
protected JsScope(@NotNull String description) {
this.description = description;
parent = null;
scopeId = null;
}
@NotNull
public JsScope innerObjectScope(@NotNull String scopeName) {
return JsObjectScope(this, scopeName);
}
/**
* Gets a name object associated with the specified identifier in this scope,
* creating it if necessary.
* If the JsName does not exist yet, a new JsName is created. The identifier,
* short name, and original name of the newly created JsName are equal to
* the given identifier.
*
* @param identifier An identifier that is unique within this scope.
*/
@NotNull
public JsName declareName(@NotNull String identifier) {
JsName name = findOwnName(identifier);
return name != null ? name : doCreateName(identifier);
}
/**
* Creates a new variable with an unique ident in this scope.
* The generated JsName is guaranteed to have an identifier that does not clash with any existing variables in the scope.
* Future declarations of variables might however clash with the temporary
* (unless they use this function).
*/
@NotNull
public JsName declareFreshName(@NotNull String suggestedName) {
assert !suggestedName.isEmpty();
String ident = getFreshIdent(suggestedName);
assert !hasOwnName(ident);
return doCreateName(ident);
}
private String getNextTempName() {
// introduced by the compiler
return "tmp$" + (scopeId != null ? scopeId + "$" : "") + tempIndex++;
}
/**
* Creates a temporary variable with an unique name in this scope.
* The generated temporary is guaranteed to have an identifier (but not short
* name) that does not clash with any existing variables in the scope.
* Future declarations of variables might however clash with the temporary.
*/
@NotNull
public JsName declareTemporary() {
return declareFreshName(getNextTempName());
}
/**
* Attempts to find the name object for the specified ident, searching in this
* scope, and if not found, in the parent scopes.
*
* @return null if the identifier has no associated name
*/
@Nullable
public final JsName findName(String ident) {
JsName name = findOwnName(ident);
if (name == null && parent != null) {
return parent.findName(ident);
}
return name;
}
public boolean hasOwnName(@NotNull String name) {
return names.containsKey(name);
}
/**
* Returns the parent scope of this scope, or null if this is the
* root scope.
*/
public final JsScope getParent() {
return parent;
}
public JsProgram getProgram() {
assert (parent != null) : "Subclasses must override getProgram() if they do not set a parent";
return parent.getProgram();
}
@Override
public final String toString() {
if (parent != null) {
return description + "->" + parent;
}
else {
return description;
}
}
public void copyOwnNames(JsScope other) {
names = new HashMap(names);
names.putAll(other.names);
}
@NotNull
public String getDescription() {
return description;
}
@NotNull
protected JsName doCreateName(@NotNull String ident) {
JsName name = new JsName(this, ident);
names = Maps.put(names, ident, name);
return name;
}
/**
* Attempts to find the name object for the specified ident, searching in this
* scope only.
*
* @return null if the identifier has no associated name
*/
protected JsName findOwnName(@NotNull String ident) {
return names.get(ident);
}
/**
* During inlining names can be refreshed multiple times,
* so "a" becomes "a_0", then becomes "a_0_0"
* in case a_0 has been declared in calling scope.
*
* That's ugly. To resolve it, we rename
* clashing names with "[_$]\\d+" suffix,
* incrementing last number.
*
* Fresh name for "a0" should still be "a0_0".
*/
@NotNull
protected String getFreshIdent(@NotNull String suggestedIdent) {
char sep = '_';
String baseName = suggestedIdent;
int counter = 0;
Matcher matcher = FRESH_NAME_SUFFIX.matcher(suggestedIdent);
if (matcher.find()) {
String group = matcher.group();
baseName = matcher.replaceAll("");
sep = group.charAt(0);
counter = Integer.valueOf(group.substring(1));
}
String freshName = suggestedIdent;
while (hasOwnName(freshName)) {
freshName = baseName + sep + counter++;
}
return freshName;
}
}