javacelements.java

是一款用JAVA 编写的编译器 具有很强的编译功能

     * symbol, and returns its RHS.  Does not scan nested JCAnnotations.
     */
    private JCExpression scanForAssign(final MethodSymbol sym,
				       final JCTree tree) {
	class TS extends TreeScanner {
	    JCExpression result = null;
	    public void scan(JCTree t) {
		if (t != null && result == null)
		    t.accept(this);
	    }
	    public void visitAnnotation(JCAnnotation t) {
		if (t == tree)
		    scan(t.args);
	    }
	    public void visitAssign(JCAssign t) {
		if (t.lhs.getTag() == JCTree.IDENT) {
		    JCIdent ident = (JCIdent) t.lhs;
		    if (ident.sym == sym)
			result = t.rhs;
		}
	    }
	}
	TS scanner = new TS();
	tree.accept(scanner);
	return scanner.result;
    }

    /**
     * Returns the tree node corresponding to this element, or null
     * if none can be found.
     */
    public JCTree getTree(Element e) {
	Pair<JCTree, ?> treeTop = getTreeAndTopLevel(e);
	return (treeTop != null) ? treeTop.fst : null;
    }

    public String getDocComment(Element e) {
	// Our doc comment is contained in a map in our toplevel,
	// indexed by our tree.  Find our enter environment, which gives
	// us our toplevel.  It also gives us a tree that contains our
	// tree:  walk it to find our tree.  This is painful.
	Pair<JCTree, JCCompilationUnit> treeTop = getTreeAndTopLevel(e);
	if (treeTop == null)
	    return null;
	JCTree tree = treeTop.fst;
	JCCompilationUnit toplevel = treeTop.snd;
        if (toplevel.docComments == null)
            return null;
	return toplevel.docComments.get(tree);
    }

    public PackageElement getPackageOf(Element e) {
	return cast(Symbol.class, e).packge();
    }

    public boolean isDeprecated(Element e) {
	Symbol sym = cast(Symbol.class, e);
	return (sym.flags() & Flags.DEPRECATED) != 0;
    }

    public Name getBinaryName(TypeElement type) {
	return cast(TypeSymbol.class, type).flatName();
    }

    public Map<MethodSymbol, Attribute> getElementValuesWithDefaults(
							AnnotationMirror a) {
	Attribute.Compound anno = cast(Attribute.Compound.class, a);
	DeclaredType annotype = a.getAnnotationType();
	Map<MethodSymbol, Attribute> valmap = anno.getElementValues();

	for (ExecutableElement ex :
		 methodsIn(annotype.asElement().getEnclosedElements())) {
	    MethodSymbol meth = (MethodSymbol) ex;
	    Attribute defaultValue = meth.getDefaultValue();
	    if (defaultValue != null && !valmap.containsKey(meth)) {
		valmap.put(meth, defaultValue);
	    }
	}
	return valmap;
    }

    /**
     * {@inheritDoc}
     */
    public FilteredMemberList getAllMembers(TypeElement element) {
	Symbol sym = cast(Symbol.class, element);
	Scope scope = sym.members().dupUnshared();
	List<Type> closure = types.closure(sym.asType());
	for (Type t : closure)
	    addMembers(scope, t);
	return new FilteredMemberList(scope);
    }
    // where
	private void addMembers(Scope scope, Type type) {
	    members:
	    for (Scope.Entry e = type.asElement().members().elems; e != null; e = e.sibling) {
		Scope.Entry overrider = scope.lookup(e.sym.getSimpleName());
		while (overrider.scope != null) {
		    if (overrider.sym.kind == e.sym.kind
			&& (overrider.sym.flags() & Flags.SYNTHETIC) == 0)
		    {
			if (overrider.sym.getKind() == ElementKind.METHOD
			&& overrides((ExecutableElement)overrider.sym, (ExecutableElement)e.sym, (TypeElement)type.asElement())) {
			    continue members;
			}
		    }
		    overrider = overrider.next();
		}
		boolean derived = e.sym.getEnclosingElement() != scope.owner;
		ElementKind kind = e.sym.getKind();
		boolean initializer = kind == ElementKind.CONSTRUCTOR
		    || kind == ElementKind.INSTANCE_INIT
		    || kind == ElementKind.STATIC_INIT;
		if (!derived || (!initializer && e.sym.isInheritedIn(scope.owner, types)))
		    scope.enter(e.sym);
	    }
	}

    /**
     * Returns all annotations of an element, whether
     * inherited or directly present.
     *
     * @param e  the element being examined
     * @return all annotations of the element
     */
    public List<Attribute.Compound> getAllAnnotationMirrors(Element e) {
	Symbol sym = cast(Symbol.class, e);
	List<Attribute.Compound> annos = sym.getAnnotationMirrors();
	while (sym.getKind() == ElementKind.CLASS) {
	    Type sup = ((ClassSymbol) sym).getSuperclass();
	    if (sup.tag != TypeTags.CLASS || sup.isErroneous() ||
		    sup.tsym == syms.objectType.tsym) {
		break;
	    }
	    sym = sup.tsym;
	    List<Attribute.Compound> oldAnnos = annos;
	    for (Attribute.Compound anno : sym.getAnnotationMirrors()) {
		if (isInherited(anno.type) &&
			!containsAnnoOfType(oldAnnos, anno.type)) {
		    annos = annos.prepend(anno);
		}
	    }
	}
	return annos;
    }

    /**
     * Tests whether an annotation type is @Inherited.
     */
    private boolean isInherited(Type annotype) {
	for (Attribute.Compound anno : annotype.tsym.getAnnotationMirrors()) {
	    if (anno.type.tsym == syms.inheritedType.tsym)
		return true;
	}
	return false;
    }

    /**
     * Tests whether a list of annotations contains an annotation
     * of a given type.
     */
    private static boolean containsAnnoOfType(List<Attribute.Compound> annos,
					      Type type) {
	for (Attribute.Compound anno : annos) {
	    if (anno.type.tsym == type.tsym)
		return true;
	}
	return false;
    }

    public boolean hides(Element hiderEl, Element hideeEl) {
	Symbol hider = cast(Symbol.class, hiderEl);
	Symbol hidee = cast(Symbol.class, hideeEl);

	// Fields only hide fields; methods only methods; types only types.
	// Names must match.  Nothing hides itself (just try it).
	if (hider == hidee ||
		hider.kind != hidee.kind ||
		hider.name != hidee.name) {
	    return false;
	}

	// Only static methods can hide other methods.
	// Methods only hide methods with matching signatures.
	if (hider.kind == Kinds.MTH) {
	    if (!hider.isStatic() ||
			!types.isSubSignature(hider.type, hidee.type)) {
		return false;
	    }
	}

	// Hider must be in a subclass of hidee's class.
	// Note that if M1 hides M2, and M2 hides M3, and M3 is accessible
	// in M1's class, then M1 and M2 both hide M3.
	ClassSymbol hiderClass = hider.owner.enclClass();
	ClassSymbol hideeClass = hidee.owner.enclClass();
	if (hiderClass == null || hideeClass == null ||
		!hiderClass.isSubClass(hideeClass, types)) {
	    return false;
	}

	// Hidee must be accessible in hider's class.
	// The method isInheritedIn is poorly named:  it checks only access.
	return hidee.isInheritedIn(hiderClass, types);
    }

    public boolean overrides(ExecutableElement riderEl,
			     ExecutableElement rideeEl, TypeElement typeEl) {
	MethodSymbol rider = cast(MethodSymbol.class, riderEl);
	MethodSymbol ridee = cast(MethodSymbol.class, rideeEl);
	ClassSymbol origin = cast(ClassSymbol.class, typeEl);

	return rider.name == ridee.name &&

	       // not reflexive as per JLS
	       rider != ridee &&

	       // we don't care if ridee is static, though that wouldn't
	       // compile
	       !rider.isStatic() &&

	       // Symbol.overrides assumes the following
	       ridee.isMemberOf(origin, types) &&

	       // check access and signatures; don't check return types
	       rider.overrides(ridee, origin, types, false);
    }

    public String getConstantExpression(Object value) {
	return Constants.format(value);
    }

    /**
     * Print a representation of the elements to the given writer in
     * the specified order.  The main purpose of this method is for
     * diagnostics.  The exact format of the output is <em>not</em>
     * specified and is subject to change.
     *
     * @param w the writer to print the output to
     * @param elements the elements to print
     */
    public void printElements(java.io.Writer w, Element... elements) {
	for (Element element : elements)
	    (new PrintingProcessor.PrintingElementVisitor(w, this)).visit(element).flush();
    }

    public Name getName(CharSequence cs) {
	return Name.fromString(names, cs.toString());
    }
    
    /**
     * Returns the tree node and compilation unit corresponding to this
     * element, or null if they can't be found.
     */
    private Pair<JCTree, JCCompilationUnit> getTreeAndTopLevel(Element e) {
	Symbol sym = cast(Symbol.class, e);
	Env<AttrContext> enterEnv = getEnterEnv(sym);
	if (enterEnv == null)
	    return null;
	JCTree tree = TreeInfo.declarationFor(sym, enterEnv.tree);
	if (tree == null || enterEnv.toplevel == null)
	    return null;
	return new Pair<JCTree,JCCompilationUnit>(tree, enterEnv.toplevel);
    }

    /**
     * Returns the best approximation for the tree node and compilation unit
     * corresponding to the given element, annotation and value.
     * If the element is null, null is returned.
     * If the annotation is null or cannot be found, the tree node and 
     * compilation unit for the element is returned.
     * If the annotation value is null or cannot be found, the tree node and 
     * compilation unit for the annotation is returned.
     */
    public Pair<JCTree, JCCompilationUnit> getTreeAndTopLevel(
		      Element e, AnnotationMirror a, AnnotationValue v) {
	if (e == null)
	    return null;

	Pair<JCTree, JCCompilationUnit> elemTreeTop = getTreeAndTopLevel(e);
	if (elemTreeTop == null)
	    return null;

	if (a == null)
	    return elemTreeTop;

	JCTree annoTree = matchAnnoToTree(a, e, elemTreeTop.fst);
	if (annoTree == null)
	    return elemTreeTop;

	// 6388543: if v != null, we should search within annoTree to find
	// the tree matching v. For now, we ignore v and return the tree of 
	// the annotation.
	return new Pair<JCTree, JCCompilationUnit>(annoTree, elemTreeTop.snd);
    }

    /**
     * Returns a symbol's enter environment, or null if it has none.
     */
    private Env<AttrContext> getEnterEnv(Symbol sym) {
	// Get enclosing class of sym, or sym itself if it is a class
	// or package.
	TypeSymbol ts = (sym.kind != Kinds.PCK)
			? sym.enclClass()
			: (PackageSymbol) sym;
	return (ts != null)
		? enter.getEnv(ts)
		: null;
    }

    /**
     * Returns an object cast to the specified type.
     * @throws NullPointerException if the object is {@code null}
     * @throws IllegalArgumentException if the object is of the wrong type
     */
    private static <T> T cast(Class<T> clazz, Object o) {
	if (! clazz.isInstance(o))
	    throw new IllegalArgumentException(o.toString());
	return clazz.cast(o);
    }
}