binder-diagnostics.md

Binder Error Reporting

Binding errors are added to the sourceFile's list of bindDiagnostics.

An example error detected during binding is the use of eval or arguments as a variable name in use strict scenario. The relevant code is presented in its entirety below (checkStrictModeEvalOrArguments is called from multiple places, call stacks originating from bindWorker which calls different functions for different node SyntaxKind):

function checkStrictModeEvalOrArguments(contextNode: Node, name: Node) {
    if (name && name.kind === SyntaxKind.Identifier) {
        let identifier = <Identifier>name;
        if (isEvalOrArgumentsIdentifier(identifier)) {
            // We check first if the name is inside class declaration or class expression; if so give explicit message
            // otherwise report generic error message.
            let span = getErrorSpanForNode(file, name);
            file.bindDiagnostics.push(createFileDiagnostic(file, span.start, span.length,
                getStrictModeEvalOrArgumentsMessage(contextNode), identifier.text));
        }
    }
}

function isEvalOrArgumentsIdentifier(node: Node): boolean {
    return node.kind === SyntaxKind.Identifier &&
        ((<Identifier>node).text === "eval" || (<Identifier>node).text === "arguments");
}

function getStrictModeEvalOrArgumentsMessage(node: Node) {
    // Provide specialized messages to help the user understand why we think they're in
    // strict mode.
    if (getContainingClass(node)) {
        return Diagnostics.Invalid_use_of_0_Class_definitions_are_automatically_in_strict_mode;
    }

    if (file.externalModuleIndicator) {
        return Diagnostics.Invalid_use_of_0_Modules_are_automatically_in_strict_mode;
    }

    return Diagnostics.Invalid_use_of_0_in_strict_mode;
}