Note that Babel now has support for this: babel/babel#12091

tc39/ecma262#2154

import { "😊" as yay } from "...";

yay();

export { yay as "🦈" };

The above code should be supported.

The minimum viable product should have tests for:

• esnext module output
• es2015 or similar module output just to get an error
• --declaration emit
  • Specific declaration emit where the compiler might generate import() type syntax.
• Quick info, and error message tests where we might generate import() type syntax
• Completions in import {} and export {} lists
• Go-to-definition

It is likely that we would never try to emit our own import() type syntax.

Is it planned for this to work with TypeScript types as well as values? For example, I'd expect the following to be valid as well:

import type { 'a' as b } from 'foo' 
import { type 'a' as b } from 'foo' 

export type { a as 'b' }
export { type a as 'b' }
export { type 'a' } from 'foo' 
export { type 'a' as b } from 'foo' 
export { type a as 'b' } from 'foo' 
export { type 'a' as 'b' } from 'foo' 

I'm wondering because esbuild supports both TypeScript and arbitrary module namespace identifier names, so it has to deal with this somehow. Right now I'm moving forward assuming that it will eventually be supported for types as well but it would be good to clarify this.

@evanw I’m pretty sure your examples above will “just work” unless we explicitly disallow them, and I don’t see an immediate reason to do that. The syntax above would certainly parse. Just out of curiosity, what’s the impact of this on esbuild?

@DanielRosenwasser should this actually be milestoned right now? It’s a bit hard to tell the status of the spec change, but it looks kinda stuck.

Good call, I assumed it would be an open-and-shut normative PR but it looks like it hasn't been updated for a while; let's hold off until tc39/ecma262#2154 is actually merged.

@andrewbranch

@DanielRosenwasser should this actually be milestoned right now? It’s a bit hard to tell the status of the spec change, but it looks kinda stuck.

Note that this is already implemented in V8, SpiderMonkey, and JavaScriptCore;

@andrewbranch @DanielRosenwasser
tc39/ecma262#2154 has now been merged.

@DanielRosenwasser do we want to make this Help Wanted for 4.6? Kind of surprised we don’t have a community PR already 😁

I suppose so - I would urge a bit of caution to external contributors because I'm sure an implementation needs to now handle a bunch of edge-cases around rename, find-all-refs, etc. Also, it might be worth erroring if the module target isn't high enough? Unclear to me right now.

👋 Hi, I'm the Repro bot. I can help narrow down and track compiler bugs across releases! This comment reflects the current state of the repro in the issue body running against the nightly TypeScript.

Issue body code block by @ExE-Boss

❌ Failed: -

• Identifier expected.
• Declaration or statement expected.
• Identifier expected.
• Declaration or statement expected.
• Identifier expected.
• Declaration or statement expected.
• Identifier expected.
• Declaration or statement expected.
• Duplicate identifier '(Missing)'.
• Duplicate identifier '(Missing)'.
• Cannot find module 'some imports' or its corresponding type declarations.
• Cannot find name 'as'.
• Cannot find name 'foo'.
• Cannot find name 'from'.
• Cannot find module 'some exports' or its corresponding type declarations.
• Cannot find name 'from'.
• Cannot find name 'as'.
• Cannot find name 'from'.
• Cannot find name 'from'.
• Cannot find name 'as'.
• Cannot find name 'extra_imports'.
• Cannot find name 'from'.
• Cannot find module 'star exports' or its corresponding type declarations.
• Cannot find name 'from'.
• Identifier expected.
• ';' expected.
• Declaration or statement expected.
• Unexpected keyword or identifier.
• Identifier expected.
• Declaration or statement expected.
• Unexpected keyword or identifier.
• Identifier expected.
• ';' expected.
• Declaration or statement expected.
• Unexpected keyword or identifier.
• Identifier expected.
• Declaration or statement expected.
• Unexpected keyword or identifier.
• Identifier expected.
• ';' expected.
• Declaration or statement expected.
• Unexpected keyword or identifier.
• Identifier expected.
• ';' expected.

as;
foo;
from;
"./module.js";
export { foo as  } from "some exports";
from;
"./module.js";
as;
"another exports";
from;
"./module.js";
from;
"./module.js";
as;
extra_imports;
from;
"./module.js";
export * as  from "star exports";
from;
"./module.js";

as;
foo;
from;
"./module.js";
export { foo as  } from "some exports";
from;
"./module.js";
as;
"another exports";
from;
"./module.js";
from;
"./module.js";
as;
extra_imports;
from;
"./module.js";
export * as  from "star exports";
from;
"./module.js";

as;
foo;
from;
"./module.js";
export { foo as  } from "some exports";
from;
"./module.js";
as;
"another exports";
from;
"./module.js";
from;
"./module.js";
as;
extra_imports;
from;
"./module.js";
export * as  from "star exports";
from;
"./module.js";

Let me try this but no guarantee I will make it

Parser and SystemJS/CommonJS emit work now. Still have no idea how I should change the type system to support analyzing that.