[Bug]: TypeScript type only import namespace aliases are not removed #15942
Description
💻
- Would you like to work on a fix?
How are you using Babel?
@babel/cli
Input code
import { X } from "abc";
// assume Y is a type only namespace
import Z = X.Y.Z;
function a(t: Z.T) {
console.log(t);
}Configuration file name
babel.config.js
Configuration
export = {
assumptions: {
},
presets: [
["@babel/preset-env", {
// preserve ES module syntax (imports, exports)
modules: false,
targets: {
firefox: "91",
chrome: "88",
edge: "88"
}
}],
["@babel/preset-typescript", {
allowNamespaces: true,
allowDeclareFields: true
}],
"@babel/preset-react"
],
plugins: [
["@babel/plugin-transform-typescript", {
allowDeclareFields: true,
}],
["@babel/plugin-proposal-decorators", {
"legacy": true
}],
["@babel/plugin-transform-class-properties", {"loose": false}],
"@babel/plugin-proposal-private-property-in-object",
"@babel/plugin-transform-runtime",
],
}Current and expected behavior
As with TypeScript, no code is now generated for type only namespaces. However, if you import a type only namespace using an import alias, code is generated for this import, which can crash at runtime. In the example input code, Z is a type only namespace with an interface T inside of if (or any other type). Since it's only used as a type in the code, the code for the alias should be removed. Instead, the generated code includes
var Z = X.Y.Z;Because Y doesn't exist (it's type only), X.Y.Z crashes (Y is undefined).
I would expect no code to be generated for import Z = X.Y.Z.
Environment
"@babel/core": "7.22.15",
"@babel/plugin-transform-class-properties": "7.22.5",
"@babel/plugin-proposal-decorators": "7.22.15",
"@babel/plugin-proposal-private-property-in-object": "7.21.11",
"@babel/plugin-transform-runtime": "7.22.15",
"@babel/plugin-transform-typescript": "7.22.15",
"@babel/preset-env": "7.22.15",
"@babel/preset-react": "7.22.15",
"@babel/preset-typescript": "7.22.15",
node 16.16.0
Possible solution
No response