Don't let the declaration file break compilation

[John0King]

Suggestion

Don't let the declaration file break compilation.
if you write a declaration file that use --nolib, and others has duplicate global class name,
or a package depends on package depA, then package depA interface name has been renamed , then your app won't compile.

The unknowed type in .d.ts should map to any, and show a warning instead of error

Use Cases

@types/libraryA from npm :

///<reference no-default-lib />
declare console:MyConsole

and @types/libraryB from npm

///<reference lib="dom" />

I create a git repo to show how this happend, and I can not find a way to solve the problem in your own source code.

Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

[DanielRosenwasser]

This would mean misspelled type names would resolve to unknown or any or whatever, which is undesirable. Consider adding a 👍 to #31894 which would allow you to state that some type name exists without knowing specifics about the implementation.

[John0King]

@DanielRosenwasser I think #31894 is not for this case ,
What I want to avoid is declaration file error , declaration file normally from third party, and there are some case that your app compile fine , your used third party declaration is compiled file, but it'll error when you add the declaration to your app.
yes I can edit the downloaded declaration but it's from npm so next time you download from network it won't compile again.

I think Typescipt should distinguish between source file and declaration file . source file can not have error , but declaration file can be tread like js （as long as it won't contains syntext error）

[John0King]

@DanielRosenwasser I added a demo to show how this happend , it does not happend in your own source code , it happend when multiple declarion library been merge to your project.
should this be reopen ?

[fatcerberus]

Have you tried --skipLibCheck?

[John0King]

@fatcerberus cool, it solve my problem 😜 . Thanks.
I never notice this options before