static_analysis.cpp

/*
Copyright 2015 Google Inc. All rights reserved.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

#include <set>

#include "static_analysis.h"
#include "static_error.h"
#include "ast.h"

typedef std::set<const Identifier *> IdSet;

/** Inserts all of s into r. */
static void append(IdSet &r, const IdSet &s)
{
    r.insert(s.begin(), s.end());
}

/** Statically analyse the given ast.
 *
 * \param ast_ The AST.
 * \param in_object Whether or not ast_ is within the lexical scope of an object AST.
 * \param vars The variables defined within lexical scope of ast_.
 * \returns The free variables in ast_.
 */
static IdSet static_analysis(AST *ast_, bool in_object, const IdSet &vars)
{
    IdSet r;

    if (auto *ast = dynamic_cast<const Apply*>(ast_)) {
        append(r, static_analysis(ast->target, in_object, vars));
        for (const auto &arg : ast->args)
            append(r, static_analysis(arg.expr, in_object, vars));

    } else if (auto *ast = dynamic_cast<const Array*>(ast_)) {
        for (auto & el : ast->elements)
            append(r, static_analysis(el.expr, in_object, vars));

    } else if (auto *ast = dynamic_cast<const Binary*>(ast_)) {
        append(r, static_analysis(ast->left, in_object, vars));
        append(r, static_analysis(ast->right, in_object, vars));

    } else if (dynamic_cast<const BuiltinFunction*>(ast_)) {
        // Nothing to do.

    } else if (auto *ast = dynamic_cast<const Conditional*>(ast_)) {
        append(r, static_analysis(ast->cond, in_object, vars));
        append(r, static_analysis(ast->branchTrue, in_object, vars));
        append(r, static_analysis(ast->branchFalse, in_object, vars));

    } else if (auto *ast = dynamic_cast<const Error*>(ast_)) {
        append(r, static_analysis(ast->expr, in_object, vars));

    } else if (auto *ast = dynamic_cast<const Function*>(ast_)) {
        auto new_vars = vars;
        IdSet params;
        for (const auto &p : ast->params) {
            if (params.find(p.id) != params.end()) {
                std::string msg = "Duplicate function parameter: " + encode_utf8(p.id->name);
                throw StaticError(ast_->location, msg);
            }
            params.insert(p.id);
            new_vars.insert(p.id);
        }

        auto fv = static_analysis(ast->body, in_object, new_vars);
        for (const auto &p : ast->params) {
            if (p.expr != nullptr)
                append(fv, static_analysis(p.expr, in_object, new_vars));
        }
        for (const auto &p : ast->params)
            fv.erase(p.id);
        append(r, fv);

    } else if (dynamic_cast<const Import*>(ast_)) {
        // Nothing to do.

    } else if (dynamic_cast<const Importstr*>(ast_)) {
        // Nothing to do.

    } else if (auto *ast = dynamic_cast<const Index*>(ast_)) {
        append(r, static_analysis(ast->target, in_object, vars));
        append(r, static_analysis(ast->index, in_object, vars));

    } else if (auto *ast = dynamic_cast<const Local*>(ast_)) {
        IdSet ast_vars;
        for (const auto &bind: ast->binds) {
            ast_vars.insert(bind.var);
        }
        auto new_vars = vars;
        append(new_vars, ast_vars);
        IdSet fvs;
        for (const auto &bind: ast->binds) {
            append(fvs, static_analysis(bind.body, in_object, new_vars));
        }

        append(fvs, static_analysis(ast->body, in_object, new_vars));

        for (const auto &bind: ast->binds)
            fvs.erase(bind.var);

        append(r, fvs);

    } else if (dynamic_cast<const LiteralBoolean*>(ast_)) {
        // Nothing to do.

    } else if (dynamic_cast<const LiteralNumber*>(ast_)) {
        // Nothing to do.

    } else if (dynamic_cast<const LiteralString*>(ast_)) {
        // Nothing to do.

    } else if (dynamic_cast<const LiteralNull*>(ast_)) {
        // Nothing to do.

    } else if (auto *ast = dynamic_cast<DesugaredObject*>(ast_)) {
        for (auto &field : ast->fields) {
            append(r, static_analysis(field.name, in_object, vars));
            append(r, static_analysis(field.body, true, vars));
        }
        for (AST *assert : ast->asserts) {
            append(r, static_analysis(assert, true, vars));
        }

    } else if (auto *ast = dynamic_cast<ObjectComprehensionSimple*>(ast_)) {
        auto new_vars = vars;
        new_vars.insert(ast->id);
        append(r, static_analysis(ast->field, false, new_vars));
        append(r, static_analysis(ast->value, true, new_vars));
        r.erase(ast->id);
        append(r, static_analysis(ast->array, in_object, vars));

    } else if (dynamic_cast<const Self*>(ast_)) {
        if (!in_object)
            throw StaticError(ast_->location, "Can't use self outside of an object.");

    } else if (auto *ast = dynamic_cast<const SuperIndex*>(ast_)) {
        if (!in_object)
            throw StaticError(ast_->location, "Can't use super outside of an object.");
        append(r, static_analysis(ast->index, in_object, vars));

    } else if (auto *ast = dynamic_cast<const Unary*>(ast_)) {
        append(r, static_analysis(ast->expr, in_object, vars));

    } else if (auto *ast = dynamic_cast<const Var*>(ast_)) {
        if (vars.find(ast->id) == vars.end()) {
            throw StaticError(ast->location, "Unknown variable: "+encode_utf8(ast->id->name));
        }
        r.insert(ast->id);

    } else {
        std::cerr << "INTERNAL ERROR: Unknown AST: " << ast_ << std::endl;
        std::abort();

    }

    for (auto *id : r)
        ast_->freeVariables.push_back(id);

    return r;
}

void jsonnet_static_analysis(AST *ast)
{
    static_analysis(ast, false, IdSet{});
}