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The Checker Framework enhances Java’s type system to make it more powerful and useful. This lets software developers detect and prevent errors in their Java programs. The Checker Framework includes compiler plug-ins ("checkers") that find bugs or verify their absence. It also permits you to write your own compiler plug-ins.

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package org.checkerframework.framework.type;

/**
 * Created by jburke on 11/20/14.
 */

import com.sun.source.tree.LambdaExpressionTree;
import com.sun.source.tree.MethodTree;
import com.sun.source.tree.Tree;
import com.sun.source.tree.Tree.Kind;
import com.sun.source.tree.VariableTree;
import org.checkerframework.framework.type.AnnotatedTypeMirror.AnnotatedDeclaredType;
import org.checkerframework.framework.type.AnnotatedTypeMirror.AnnotatedExecutableType;
import org.checkerframework.javacutil.Pair;
import org.checkerframework.javacutil.TreeUtils;

import javax.lang.model.element.Element;
import javax.lang.model.element.ExecutableElement;

/**
 * Converts a field or methods tree tree into an AnnotatedTypeMirror
 *
 * @see org.checkerframework.framework.type.TypeFromTree
 */
class TypeFromMemberVisitor extends TypeFromTreeVisitor {

    @Override
    public AnnotatedTypeMirror visitVariable(VariableTree node,
                                             AnnotatedTypeFactory f) {
        AnnotatedTypeMirror result = f.fromTypeTree(node.getType());
        result.clearAnnotations();
        Element elt = TreeUtils.elementFromDeclaration(node);

        ElementAnnotationApplier.apply(result, elt, f);
        inferLambdaParamAnnotations(f, result, elt);
        return result;

            /* An alternative I played around with. It unfortunately
             * ignores stub files, which is not good.
            com.sun.tools.javac.code.Type undType = ((JCTree)node).type;
            AnnotatedTypeMirror result;

            if (undType != null) {
                result = f.toAnnotatedType(undType);
            } else {
                // node.getType() ignores the top-level modifiers, which are
                // in node.getModifiers()
                result = f.fromTypeTree(node.getType());
                // We still need to remove all annotations.
                // result.clearAnnotations();
            }

            // TODO: Additionally decoding should NOT be necessary.
            // However, the underlying javac Type doesn't contain
            // type argument annotations.
            Element elt = TreeUtils.elementFromDeclaration(node);
            ElementAnnotationUtils.apply(result, elt, f);

            return result;*/
    }

    @Override
    public AnnotatedTypeMirror visitMethod(MethodTree node,
                                           AnnotatedTypeFactory f) {

        ExecutableElement elt = TreeUtils.elementFromDeclaration(node);

        AnnotatedExecutableType result =
                (AnnotatedExecutableType)f.toAnnotatedType(elt.asType(), false);
        result.setElement(elt);

        ElementAnnotationApplier.apply(result, elt, f);

        return result;
    }

    private static void inferLambdaParamAnnotations(AnnotatedTypeFactory f, AnnotatedTypeMirror result, Element paramElement) {
        if (f.declarationFromElement(paramElement) == null
                || f.getPath(f.declarationFromElement(paramElement)) == null
                || f.getPath(f.declarationFromElement(paramElement)).getParentPath() == null) {

            return;
        }
        Tree declaredInTree = f.getPath(f.declarationFromElement(paramElement)).getParentPath().getLeaf();
        if (declaredInTree.getKind() == Kind.LAMBDA_EXPRESSION) {
            LambdaExpressionTree lambdaDecl = (LambdaExpressionTree)declaredInTree;
            int index = lambdaDecl.getParameters().indexOf(f.declarationFromElement(paramElement));
            Pair res = f.getFnInterfaceFromTree(lambdaDecl);
            AnnotatedExecutableType fnMethod = res.second;
            AnnotatedTypeMirror declaredParam = fnMethod.getParameterTypes().get(index);
            // TODO: Should we infer nested types (e.g. List<@x String>)
            result.addMissingAnnotations(declaredParam.getAnnotations());
        }
    }
}