Elide empty named imports next to a default import under verbatimModuleSyntax

[Maksim Romanov (maksim-romanov)]

Fixes #62239

With verbatimModuleSyntax on, tsc kept an empty {} after a default import when all the named imports were type-only:

import A, { type T } from "./a";
// before: import A, {} from "./a";
// after:  import A from "./a";

The default binding keeps the import, so the braces do nothing there. Imports without a default binding still emit import {} from "./a", and a {} you write in the source stays. 6.0 emits the braces too, and this PR changes that. Ryan approved the same change for the old codebase in #62349 before the bot closed it during the 6.0 freeze.

I wrote this change with Claude Code. I chose this issue, read and understand the change, and will handle review feedback myself.

[Maksim Romanov (maksim-romanov)]

@microsoft-github-policy-service agree

[Copilot]

Copilot review overview

🟢 Approval recommended

The narrow guard matches the intended behavior, regression cases cover its boundaries, and no blocking issues were identified.

Review effort: Balanced
Findings: None

What changed in this PR

Fixes #62239 by dropping named-import braces emptied by type erasure when a default import remains under verbatimModuleSyntax.

Changes:

• Updates the type eraser while preserving source-written {} and imports without a default binding.
• Adds regression coverage and matching emit, type, and symbol baselines.

File	Description
tsc/​testdata/​tests/​cases/​compiler/​verbatimModuleSyntaxDefaultImportTypeOnlyNamed.ts	Tests elision and preservation cases.
tsc/​testdata/​baselines/​reference/​compiler/​verbatimModuleSyntaxDefaultImportTypeOnlyNamed.types	Records expected types.
tsc/​testdata/​baselines/​reference/​compiler/​verbatimModuleSyntaxDefaultImportTypeOnlyNamed.symbols	Records expected symbols.
tsc/​testdata/​baselines/​reference/​compiler/​verbatimModuleSyntaxDefaultImportTypeOnlyNamed.js	Records expected import emission.
tsc/​internal/​transformers/​tstransforms/​typeeraser.go	Removes redundant empty named bindings.

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[Jake Bailey (jakebailey)]

I thought this behavior was intentional? Andrew Branch (@andrewbranch)

[Maksim Romanov (maksim-romanov)]

Ryan marked #62239 Help Wanted and approved the same fix in #62349. import { type T } still emits import {}, only the default import case changes.

[Jake Bailey (jakebailey)]

Yes, because import { type Foo } from "foo" means "erase Foo", which nets import {} from "foo". This is also how erasable types works in Node, 99% sure.

[Maksim Romanov (maksim-romanov)]

Makes sense. Node's type stripping, ts-blank-space and esbuild all keep the {} too, so the current output is the consistent one. Closing.

[Jake Bailey (jakebailey)]

Sorry, I misread the issue; I didn't realize that the first default import was not also a type import. I think eliding the {} is fine so long as default is not a type import.

[Jake Bailey (jakebailey)]

import type A1, { type T } is illegal already, because we smartly realized this would be ambiguous 🤦