Context.swift

// Copyright 2020 Google LLC
//
// 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
//
// https://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.

/// Current context in the program
public struct Context: OptionSet {
    public let rawValue: UInt32

    public init(rawValue: UInt32) {
        self.rawValue = rawValue
    }

    // Default javascript context.
    public static let javascript        = Context(rawValue: 1 << 0)
    // Inside a subroutine (function, constructor, method, ...) definition.
    // This for example means that doing `return` or accessing `arguments` is allowed.
    public static let subroutine        = Context(rawValue: 1 << 1)
    // Inside a generator function definition.
    // This for example means that `yield` and `yield*` are allowed.
    public static let generatorFunction = Context(rawValue: 1 << 2)
    // Inside an async function definition.
    // This for example means that `await` is allowed.
    public static let asyncFunction     = Context(rawValue: 1 << 3)
    // Inside a method.
    // This for example means that access to `super` is allowed.
    public static let method            = Context(rawValue: 1 << 4)
    // Inside a class method.
    // This for example means that access to private properties is allowed.
    public static let classMethod       = Context(rawValue: 1 << 5)
    // Inside a loop.
    public static let loop              = Context(rawValue: 1 << 6)
    // Inside a with statement.
    public static let with              = Context(rawValue: 1 << 7)
    // Inside an object literal.
    public static let objectLiteral     = Context(rawValue: 1 << 8)
    // Inside a class definition.
    public static let classDefinition   = Context(rawValue: 1 << 9)
    // Inside a switch block.
    public static let switchBlock       = Context(rawValue: 1 << 10)
    // Inside a switch case.
    public static let switchCase        = Context(rawValue: 1 << 11)
    // Inside a wasm module
    public static let wasm              = Context(rawValue: 1 << 12)
    // Inside a function in a wasm module
    public static let wasmFunction      = Context(rawValue: 1 << 13)
    // Inside a block of a wasm function, allows branches
    public static let wasmBlock         = Context(rawValue: 1 << 14)
    // Inside a block
    public static let codeBlock         = Context(rawValue: 1 << 15)
    // Inside a if|else block
    public static let ifBlock           = Context(rawValue: 1 << 16)
    // Inside a try|catch block
    public static let tryBlock          = Context(rawValue: 1 << 17)

    public static let empty             = Context([])

    // These contexts have ValueGenerators and as such we can .buildPrefix in them.
    public var isValueBuildableContext: Bool {
        self.contains(.wasmFunction) || self.contains(.javascript)
    }

    public var inWasm: Bool {
        // .wasmBlock is propagating surrounding context
        self.contains(.wasm) || self.contains(.wasmFunction)
    }
}