Disallow 'readonly' modifier in ambient module import attributes types - #64181
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Gabriela Araujo Britto (gabritto) merged 2 commits intoSep 8, 2026
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microsoft#64143) Ambient module import attributes types should not accept the 'readonly' modifier. Adds diagnostic TS1558 ("An import attributes property cannot have a 'readonly' modifier.") and checks for modifiers in checkGrammarImportAttributesType. Fixes microsoft#64143.
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🟡 Changes recommended
The modifier check incorrectly reports non-readonly modifiers as readonly.
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Pull request overview
Adds validation rejecting readonly properties in ambient-module import attribute types.
Changes:
- Adds TS1558 and grammar validation.
- Adds compiler regression coverage and baseline.
File summaries
| File | Description |
|---|---|
grammarchecks.go |
Validates attribute property modifiers. |
diagnosticMessages.json |
Defines TS1558. |
diagnostics_generated.go |
Registers generated diagnostic. |
importAttributeTypeReadonly.ts |
Adds regression cases. |
importAttributeTypeReadonly.errors.txt |
Records expected diagnostics. |
Review details
Files not reviewed (1)
- tsc/internal/diagnostics/diagnostics_generated.go: Generated file
- Files reviewed: 4/5 changed files
- Comments generated: 1
- Review effort level: Balanced
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@microsoft-github-policy-service agree |
Gabriela Araujo Britto (gabritto)
approved these changes
Sep 8, 2026
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Fixes #64143
Description
Support for import attributes on ambient module declarations (
declare module "*.css" with { type: "css" }) was added in #63931. However,readonlymodifier on attribute properties was previously accepted without error becausecheckGrammarModifiersskipsreadonlyfor property signatures (as it is normally valid on type literal properties).This PR:
readonly) on property signatures incheckGrammarImportAttributesType.readonlyattributes and valid non-readonlyattributes.