I am trying to write an annotation processor in the JSR 269 format which uses javac's Compiler Tree API to do some source code analysis. I am interested in member select expressions, such as method calls.
I can easily get the name of the method (or field, etc.) being selected. But I want to know what type the member is being selected from, and I cannot seem to find a straightforward way to do this. Trees.getTypeMirror returns null for everything I try calling it on (and the Javadoc gives no hints).
I suppose I could exhaustively analyze every kind of expression on the left side of the member select and determine the static type of the expression by recursive analysis: NewClassTree, TypeCastTree, MethodInvocationTree, ArrayAccessTree, and many others. But this seems like a lot of error-prone work, and clearly javac already knows the static type of the expression since it needs this information for many purposes. But how do I get access to this type information?
What I have so far:
import com.sun.source.tree.MemberSelectTree;
import com.sun.source.tree.MethodInvocationTree;
import com.sun.source.util.TreePath;
import com.sun.source.util.TreePathScanner;
import com.sun.source.util.Trees;
import java.util.Set;
import javax.annotation.processing.AbstractProcessor;
import javax.annotation.processing.RoundEnvironment;
import javax.annotation.processing.SupportedAnnotationTypes;
import javax.annotation.processing.SupportedSourceVersion;
import javax.lang.model.SourceVersion;
import javax.lang.model.element.Element;
import javax.lang.model.element.TypeElement;
@SupportedAnnotationTypes("*")
@SupportedSourceVersion(SourceVersion.RELEASE_6)
public class PublicProcessor extends AbstractProcessor {
public @Override boolean process(Set<? extends TypeElement> annotations, RoundEnvironment roundEnv) {
for (Element e : roundEnv.getRootElements()) {
final Trees trees = Trees.instance(processingEnv);
final TreePath root = trees.getPath(e);
new TreePathScanner<Void,Void>() {
public @Override Void visitMethodInvocation(MethodInvocationTree node, Void p) {
System.err.println("visiting method invocation: " + node + " of kind: " + node.getMethodSelect().getKind());
TreePath expr = TreePath.getPath(root, node);
System.err.println(" of type: " + trees.getTypeMirror(expr));
return super.visitMethodInvocation(node, p);
}
public @Override Void visitMemberSelect(MemberSelectTree node, Void p) {
System.err.println("accessing member: " + node.getIdentifier());
System.err.println(" from: " + getCurrentPath().getCompilationUnit().getSourceFile().toUri());
TreePath expr = TreePath.getPath(root, node.getExpression());
System.err.println(" in expr: " + expr.getLeaf());
System.err.println(" of type: " + trees.getTypeMirror(expr));
return super.visitMemberSelect(node, p);
}
}.scan(root, null);
}
return true;
}
}
and what it prints when run on some simple code making method calls:
visiting method invocation: new Class().method() of kind: MEMBER_SELECT
of type: null
accessing member: method
from: .../Whatever.java
in expr: new Class()
of type: null
