Compiler throws with "Declaration to checkResolvedBlockScopedVariable is undefined"

[athasach]

TypeScript Version: 3.1.0-dev.20180912

Search Terms:

• checkResolvedBlockScopedVariable

Code

/**
 * @enum {string} <-- Commenting this out sucessfully compiles
 */
var DICTIONARY: { [key: string]: string } = {
    '&': '&amp;'
};

// Or commenting out this function causes the compilation to succeed.
function lookup(s: string): string {
    return DICTIONARY[s] || "";
}

Expected behavior:

• Should compile without error.

Actual behavior:

If the @enum {string} comment is removed or if the function is commented out, the compiler will be successful. Otherwise, if the function is present and the @enum {string} is present it will not.

/Users/athasach/dev/research/ts3.1_bug/node_modules/typescript/lib/tsc.js:69144
                throw e;
                ^

Error: Debug Failure. Declaration to checkResolvedBlockScopedVariable is undefined
    at checkResolvedBlockScopedVariable (/Users/athasach/dev/research/ts3.1_bug/node_modules/typescript/lib/tsc.js:25869:33)
    at resolveNameHelper (/Users/athasach/dev/research/ts3.1_bug/node_modules/typescript/lib/tsc.js:25720:25)
    at resolveName (/Users/athasach/dev/research/ts3.1_bug/node_modules/typescript/lib/tsc.js:25487:20)
    at getResolvedSymbol (/Users/athasach/dev/research/ts3.1_bug/node_modules/typescript/lib/tsc.js:35871:21)
    at checkIdentifier (/Users/athasach/dev/research/ts3.1_bug/node_modules/typescript/lib/tsc.js:37132:26)
    at checkExpressionWorker (/Users/athasach/dev/research/ts3.1_bug/node_modules/typescript/lib/tsc.js:42140:28)
    at checkExpression (/Users/athasach/dev/research/ts3.1_bug/node_modules/typescript/lib/tsc.js:42116:42)
    at checkNonNullExpression (/Users/athasach/dev/research/ts3.1_bug/node_modules/typescript/lib/tsc.js:39149:37)
    at checkIndexedAccess (/Users/athasach/dev/research/ts3.1_bug/node_modules/typescript/lib/tsc.js:39465:30)
    at checkExpressionWorker (/Users/athasach/dev/research/ts3.1_bug/node_modules/typescript/lib/tsc.js:42168:28)

Playground Link:

https://www.typescriptlang.org/play/index.html#src=%2F**%0D%0A%20*%20%40enum%20%7Bstring%7D%20%3C--%20Commenting%20this%20out%20sucessfully%20compiles%0D%0A%20*%2F%0D%0Avar%20DICTIONARY%3A%20%7B%20%5Bkey%3A%20string%5D%3A%20string%20%7D%20%3D%20%7B%0D%0A%20%20%20%20'%26'%3A%20'%26amp%3B'%0D%0A%7D%3B%0D%0A%0D%0A%2F%2F%20Or%20commenting%20out%20this%20function%20causes%20the%20compilation%20to%20succeed.%0D%0Afunction%20lookup(s%3A%20string)%3A%20string%20%7B%0D%0A%20%20%20%20return%20DICTIONARY%5Bs%5D%20%7C%7C%20%22%22%3B%0D%0A%7D

Related Issues:

• Maybe typeof operator fails on use-before-defined block scoped variable. #8775

[felixfbecker]

@Andy-MS I am still seeing this error in 3.1.0-dev.20180915

Debug Failure. Declaration to checkResolvedBlockScopedVariable is undefined

    at checkResolvedBlockScopedVariable (node_modules/typescript/lib/typescript.js:31697:33)
    at resolveNameHelper (node_modules/typescript/lib/typescript.js:31538:25)
    at resolveName (node_modules/typescript/lib/typescript.js:31219:20)
    at getResolvedSymbol (node_modules/typescript/lib/typescript.js:43026:21)
    at checkIdentifier (node_modules/typescript/lib/typescript.js:44474:26)
    at checkExpressionWorker (node_modules/typescript/lib/typescript.js:50599:28)
    at checkExpression (node_modules/typescript/lib/typescript.js:50571:42)
    at checkNonNullExpression (node_modules/typescript/lib/typescript.js:47062:37)
    at checkPropertyAccessExpressionOrQualifiedName (node_modules/typescript/lib/typescript.js:47088:28)
    at checkPropertyAccessExpression (node_modules/typescript/lib/typescript.js:47081:20)

[felixfbecker]

I tried all TypeScript versions with a script and found that the error was introduced in 3.1.0-dev.20180906. The last working version was 3.1.0-dev.20180905. Unfortunately, I am depending on a different bug fix from a later version so I cannot downgrade.