Error: Debug Failure. False expression.

[calebpitan]

Bug Report

🔎 Search Terms

debug failure, false expression, at object.first

🕗 Version & Regression Information

• This is a crash
• This is the behavior in every version I tried, 4.9.5, and I reviewed the FAQ for entries about it
• I was unable to test this on prior versions because I had other issues with prior versions that made me update to a later version

⏯ Playground Link

Playground link with relevant code

💻 Code

stack trace:

/Users/calebpitan/source/work/zendwa/emailing-service/node_modules/typescript/lib/tsc.js:99615
                throw e;
                ^

Error: Debug Failure. False expression.
    at Object.first (/Users/calebpitan/source/work/zendwa/emailing-service/node_modules/typescript/lib/tsc.js:990:18)
    at getSpecifierForModuleSymbol (/Users/calebpitan/source/work/zendwa/emailing-service/node_modules/typescript/lib/tsc.js:45313:36)
    at serializeAsAlias (/Users/calebpitan/source/work/zendwa/emailing-service/node_modules/typescript/lib/tsc.js:46419:107)
    at serializeSymbolWorker (/Users/calebpitan/source/work/zendwa/emailing-service/node_modules/typescript/lib/tsc.js:46084:25)
    at serializeSymbol (/Users/calebpitan/source/work/zendwa/emailing-service/node_modules/typescript/lib/tsc.js:45978:25)
    at /Users/calebpitan/source/work/zendwa/emailing-service/node_modules/typescript/lib/tsc.js:45963:29
    at Map.forEach (<anonymous>)
    at visitSymbolTable (/Users/calebpitan/source/work/zendwa/emailing-service/node_modules/typescript/lib/tsc.js:45962:81)
    at symbolTableToDeclarationStatements (/Users/calebpitan/source/work/zendwa/emailing-service/node_modules/typescript/lib/tsc.js:45847:17)
    at /Users/calebpitan/source/work/zendwa/emailing-service/node_modules/typescript/lib/tsc.js:44127:106

Node.js v18.11.0

source: node_modules/typescript/lib/tsc.js

ts.firstOrUndefined = firstOrUndefined;
first(array) {
    ts.Debug.assert(array.length !== 0);
    return array[0];
}
ts.first = first;

tsconfig.json:

{
  "compilerOptions": {
    "module": "ES2020",
    "moduleResolution": "node",
    "allowJs": true,
    "checkJs": false,
    "declaration": true,
    "removeComments": true,
    "emitDecoratorMetadata": true,
    "experimentalDecorators": true,
    "allowSyntheticDefaultImports": true,
    "esModuleInterop": true,
    "target": "ES2022",
    "sourceMap": true,
    "outDir": "./dist",
    "baseUrl": "./",
    "rootDir": "./",
    "incremental": true,
    "skipLibCheck": true,
    "strict": true,
    "strictNullChecks": true,
    "noImplicitAny": true,
    "noImplicitThis": true,
    "strictBindCallApply": true,
    "alwaysStrict": true,
    "forceConsistentCasingInFileNames": true,
    "noFallthroughCasesInSwitch": true,
    "paths": {
      "@/shared/*": ["backend-services-shared/src/*"], // contains .js files
      "@/utils/*": ["src/utils/*"],
      "@/modules/*": ["src/modules/*"]
    }
  },
  "exclude": ["node_modules", "test", "dist"]
}

🙁 Actual behavior

Error happens when I turn on allowJs

🙂 Expected behavior

allowJs shouldn't crash build process and should include the js files from the source in the build output 😔

[RyanCavanaugh]

We'd need a way to reproduce the problem. Do you have a repo we can clone, or other way to produce this crash?

[DanielRosenwasser]

To help narrow it down, you might be able to modify your tsc.js at /Users/calebpitan/source/work/zendwa/emailing-service/node_modules/typescript/lib/tsc.js

                  symbolTableToDeclarationStatements: function (symbolTable, enclosingDeclaration, flags, tracker, bundled) {
+                     console.log("FILE NAME", ts.getSourceFileOfNode(enclosingDeclaration).fileName);
                      return withContext(enclosingDeclaration, flags, tracker, function (context) { return symbolTableToDeclarationStatements(symbolTable, context, bundled); });
                  },

It starts at line 44125 in TypeScript 4.9.5's tsc.js.

[calebpitan]

Thanks to @DanielRosenwasser "debug snippet" which seems to have pointed me in the right direction, and did help narrow it down just as he mentioned.
I inserted a console statement on that line and it was able to log the filenames till it crashed again. I inspected the last logged file before crash and found out it imported files that imported uninstalled modules/deps.

Instaliing the missing module fixed it and tsc could build successfully.

But this doesn't mean there's no problem. The problem is: the compiler couldn't resolve a specifier, why couldn't it just say so in an understandable, helpful error message, rather than an elusive jargon like "Error: Debug Failure. False expression."?

first(array) {
    ts.Debug.assert(array.length !== 0);
    return array[0];
}

It seems, apparently, the only thing that makes this array empty is an unresolved module specifier, if so, the Debug.assert could make room for a custom error message rather than a generic "Debug Failure. False expression"

[fatcerberus]

But this doesn't mean there's no problem. The problem is: the compiler couldn't resolve a specifier, why couldn't it just say so in an understandable, helpful error message, rather than an elusive jargon like "Error: Debug Failure. False expression."?

The message is cryptic because it's intended for TS developers, not end-users. A debug assert being hit means the compiler has done something that, if it were functioning correctly, would literally never happen (in this case calling first() with an empty array); it always indicates a bug that has to be fixed elsewhere. In this case, it sounds like there might be a missing check during module specifier resolution.

In other words: "Debug Failure" is a crash, not an expected error condition.

[ljharb]

I got this same error.

Specifically, it seems like I had @types/gopd installed, and then also made a types/gopd/index.d.ts, in which I provided my own definition that uses export =. @RyanCavanaugh can you reproduce it with that approach?

Note that it does not crash when my overload uses export default, but every CJS module's type is export = so I need to use that.

[DanielRosenwasser]

I tried briefly, but haven't gotten far. Can you do the same thing I told @calebpitan to try above and see if you can provide a pared down version of that file? A pared-down config file is going to be helpful too.

[ljharb]

@DanielRosenwasser when i apply that console log diff (which is slightly tricker in TS 5 beta), it's never hit - the line it dies on is Debug.assert(node.kind !== 257 /* VariableDeclaration */); inside checkAliasSymbol, and when i add a console.log(node) in front of it, i get:

<ref *2> Node4 {
  pos: 64,
  end: 88,
  kind: 257,
  id: 0,
  flags: 262144,
  modifierFlagsCache: 536875008,
  transformFlags: 0,
  parent: <ref *1> Node4 {
    pos: 59,
    end: 88,
    kind: 258,
    id: 0,
    flags: 262144,
    modifierFlagsCache: 536875008,
    transformFlags: 4194304,
    parent: Node4 {
      pos: 59,
      end: 89,
      kind: 240,
      id: 0,
      flags: 262144,
      modifierFlagsCache: 536875008,
      transformFlags: 4194304,
      parent: [Node4],
      original: undefined,
      emitNode: undefined,
      modifiers: undefined,
      declarationList: [Circular *1],
      jsDoc: undefined,
      flowNode: [Object]
    },
    original: undefined,
    emitNode: undefined,
    declarations: [
      [Circular *2],
      pos: 64,
      end: 88,
      hasTrailingComma: false,
      transformFlags: 0
    ]
  },
  original: undefined,
  emitNode: undefined,
  symbol: Symbol4 {
    flags: 2097152,
    escapedName: '$gOPD',
    declarations: [ [Circular *2] ],
    valueDeclaration: undefined,
    id: 24904,
    mergeId: 0,
    parent: undefined,
    members: undefined,
    exports: undefined,
    exportSymbol: undefined,
    constEnumOnlyModule: undefined,
    isReferenced: undefined,
    isAssigned: undefined,
    links: undefined
  },
  localSymbol: undefined,
  name: Identifier2 {
    pos: 64,
    end: 70,
    kind: 79,
    id: 0,
    flags: 262144,
    transformFlags: 0,
    parent: [Circular *2],
    original: undefined,
    emitNode: undefined,
    escapedText: '$gOPD',
    jsDoc: undefined,
    flowNode: { flags: 2064, antecedent: [Object], node: [Node4] },
    symbol: undefined
  },
  exclamationToken: undefined,
  type: undefined,
  initializer: <ref *3> Node4 {
    pos: 72,
    end: 88,
    kind: 210,
    id: 0,
    flags: 262144,
    modifierFlagsCache: 0,
    transformFlags: 0,
    parent: [Circular *2],
    original: undefined,
    emitNode: undefined,
    symbol: undefined,
    localSymbol: undefined,
    expression: Identifier2 {
      pos: 72,
      end: 80,
      kind: 79,
      id: 0,
      flags: 262144,
      transformFlags: 0,
      parent: [Circular *3],
      original: undefined,
      emitNode: undefined,
      escapedText: 'require',
      jsDoc: undefined,
      flowNode: [Object],
      symbol: undefined
    },
    questionDotToken: undefined,
    typeArguments: undefined,
    arguments: [
      [Node4],
      pos: 81,
      end: 87,
      hasTrailingComma: false,
      transformFlags: 0
    ]
  },
  jsDoc: [ jsDocCache: [] ]
}

Happy to debug live elsewhere, or with comments here, since it's consistently reproducible for me - just not in a branch i'm ready to share publicly.

Config file:

{
  "compilerOptions": {
    /* Visit https://aka.ms/tsconfig.json to read more about this file */

    /* Language and Environment */
    "target": "es2022",                                  /* Set the JavaScript language version for emitted JavaScript and include compatible library declarations. */
    // "lib": [],                                        /* Specify a set of bundled library declaration files that describe the target runtime environment. */
    "useDefineForClassFields": true,                     /* Emit ECMAScript-standard-compliant class fields. */

    /* Modules */
    "module": "commonjs",                                /* Specify what module code is generated. */
    // "rootDir": "./",                                  /* Specify the root folder within your source files. */
    // "moduleResolution": "node",                       /* Specify how TypeScript looks up a file from a given module specifier. */
    // "baseUrl": "./",                                  /* Specify the base directory to resolve non-relative module names. */
    // "paths": {},                                      /* Specify a set of entries that re-map imports to additional lookup locations. */
    // "rootDirs": [],                                   /* Allow multiple folders to be treated as one when resolving modules. */
    "typeRoots": ["types", "@node_modules/@types"],                                  /* Specify multiple folders that act like `./node_modules/@types`. */
    // "types": [],                                      /* Specify type package names to be included without being referenced in a source file. */
    // "allowUmdGlobalAccess": true,                     /* Allow accessing UMD globals from modules. */
    // "resolveJsonModule": true,                        /* Enable importing .json files */
    // "noResolve": true,                                /* Disallow `import`s, `require`s or `<reference>`s from expanding the number of files TypeScript should add to a project. */

    /* JavaScript Support */
    "allowJs": true,                                  /* Allow JavaScript files to be a part of your program. Use the `checkJS` option to get errors from these files. */
    "checkJs": true,                                  /* Enable error reporting in type-checked JavaScript files. */
    // "maxNodeModuleJsDepth": 1,                        /* Specify the maximum folder depth used for checking JavaScript files from `node_modules`. Only applicable with `allowJs`. */

    /* Emit */
    "noEmit": true,                                   /* Disable emitting files from a compilation. */

    /* Interop Constraints */
    "allowSyntheticDefaultImports": true,                /* Allow 'import x from y' when a module doesn't have a default export. */
    "esModuleInterop": true,                             /* Emit additional JavaScript to ease support for importing CommonJS modules. This enables `allowSyntheticDefaultImports` for type compatibility. */
    "forceConsistentCasingInFileNames": true,            /* Ensure that casing is correct in imports. */

    /* Type Checking */
    "strict": true,                                      /* Enable all strict type-checking options. */
    "noImplicitAny": true,                            /* Enable error reporting for expressions and declarations with an implied `any` type.. */
    "strictNullChecks": true,                         /* When type checking, take into account `null` and `undefined`. */
    "strictFunctionTypes": true,                      /* When assigning functions, check to ensure parameters and the return values are subtype-compatible. */
    "strictBindCallApply": true,                      /* Check that the arguments for `bind`, `call`, and `apply` methods match the original function. */
    "strictPropertyInitialization": true,             /* Check for class properties that are declared but not set in the constructor. */
    "noImplicitThis": true,                           /* Enable error reporting when `this` is given the type `any`. */
    "useUnknownInCatchVariables": true,               /* Type catch clause variables as 'unknown' instead of 'any'. */
    "alwaysStrict": true,                             /* Ensure 'use strict' is always emitted. */
    "noUnusedLocals": true,                           /* Enable error reporting when a local variables aren't read. */
    "noUnusedParameters": true,                       /* Raise an error when a function parameter isn't read */
    "exactOptionalPropertyTypes": true,               /* Interpret optional property types as written, rather than adding 'undefined'. */
    "noImplicitReturns": true,                        /* Enable error reporting for codepaths that do not explicitly return in a function. */
    "noFallthroughCasesInSwitch": true,               /* Enable error reporting for fallthrough cases in switch statements. */
    "noUncheckedIndexedAccess": true,                 /* Include 'undefined' in index signature results */
    "noImplicitOverride": true,                       /* Ensure overriding members in derived classes are marked with an override modifier. */
    "noPropertyAccessFromIndexSignature": true,       /* Enforces using indexed accessors for keys declared using an indexed type */

    /* Completeness */
    // "skipLibCheck": true                                 /* Skip type checking all .d.ts files. */
  },
  "include": [
    "**/*.js"
  ],
  "exclude": [
    "coverage/**"
  ],
}

[DanielRosenwasser]

That seems like a separate stack trace then, right? If so, what is the stack trace? And can you switch the console.log(node) to console.log("FILE NAME", ts.getSourceFileOfNode(enclosingDeclaration).fileName);?

[ljharb]

I can't, because ts is not defined in that function.

Stack trace:

$PWD/node_modules/typescript/lib/tsc.js:113967
      throw e;
      ^

Error: Debug Failure. False expression.
    at checkAliasSymbol ($PWD/node_modules/typescript/lib/tsc.js:78641:17)
    at checkVariableLikeDeclaration ($PWD/node_modules/typescript/lib/tsc.js:76204:7)
    at checkVariableDeclaration (/$PWD/node_modules/typescript/lib/tsc.js:76287:5)
    at checkSourceElementWorker ($PWD/node_modules/typescript/lib/tsc.js:79258:16)
    at checkSourceElement ($PWD/node_modules/typescript/lib/tsc.js:79089:7)
    at forEach ($PWD/node_modules/typescript/lib/tsc.js:37:22)
    at checkVariableStatement ($PWD/node_modules/typescript/lib/tsc.js:76297:5)
    at checkSourceElementWorker ($PWD/node_modules/typescript/lib/tsc.js:79227:16)
    at checkSourceElement ($PWD/node_modules/typescript/lib/tsc.js:79089:7)
    at forEach ($PWD/node_modules/typescript/lib/tsc.js:37:22)

Node.js v19.6.1

[ljharb]

@DanielRosenwasser actually turns out i was authoring my "declare module" incorrectly - i was doing type x = whatever instead of function x, and the export = with the type was what was crashing. Hope that helps :-)

[divmgl]

This is happening to me on version 5.3.3 of TypeScript.

I'm going to try 5.4.5 to see if this is resolved.

[DanielRosenwasser]

@divmgl that seems like an unrelated stack trace. Feel free to open a separate issue if you can provide a repro on the latest version of TS.

[zigcccc]

I'm getting this too after updating from 5.2.2 to 5.6.2. Similar to others reporting this, I have allowJs: true set.

[Andarist]

@zigcccc could you prepare a repro case of the problem? you could try to remove as much lines from your project as possible (gradually) and bisect the problem this way to the minimal repro case