npm run build failing

[erikh2000]

Hi! Today, I made a fresh fork of wavefile and then executed...

git clone git@github.com:erikh2000/wavefile.git
cd wavefile
npm install
npm run build

The build fails with several error messages along these lines (can post the full spiel, if you like):

../../node_modules/@types/jest/index.d.ts:458:62 - error TS1005: ']' expected.

458     type NonFunctionPropertyNames<T> = keyof { [K in keyof T as T[K] extends Func ? never : K]: T[K] };

../../node_modules/@types/jest/index.d.ts:458:65 - error TS1005: ';' expected.

458     type NonFunctionPropertyNames<T> = keyof { [K in keyof T as T[K] extends Func ? never : K]: T[K] };
                                                                    ~

../../node_modules/@types/jest/index.d.ts:458:70 - error TS1005: ';' expected.

458     type NonFunctionPropertyNames<T> = keyof { [K in keyof T as T[K] extends Func ? never : K]: T[K] };
                                                                         ~~~~~~~

../../node_modules/@types/jest/index.d.ts:458:94 - error TS1005: ';' expected.

458     type NonFunctionPropertyNames<T> = keyof { [K in keyof T as T[K] extends Func ? never : K]: T[K] };
                                                                                                 ~

../../node_modules/@types/jest/index.d.ts:458:95 - error TS1128: Declaration or statement expected.

458     type NonFunctionPropertyNames<T> = keyof { [K in keyof T as T[K] extends Func ? never : K]: T[K] };

This output is coming more specifically from executing the tsc ./test/TypeScript/index.ts command in the test-tsc package.json script:

No preceding commands, e.g. rollup -c, are outputting failure messages.

I promise I didn't change anything in my fork. Any ideas on how to fix? Maybe there is an uncommitted file on somebody's local directory, e.g. tsconfig.json? Or a global NPM package that is relied upon? Or I'm building with the wrong version of node or npm?