Support source phase imports by a-tarasyuk · Pull Request #63915 · microsoft/TypeScript

Oleksandr Tarasiuk (a-tarasyuk) · 2026-08-20T13:37:53Z

Fixes #61216

This patch adds support for TC39 Source Phase Imports

Copilot

Pull request overview

Adds TC39 source-phase import support across parsing, resolution, checking, emit, APIs, and language services.

Changes:

Supports static import source and dynamic import.source().
Adds phase-aware resolution, WebAssembly typing, diagnostics, and emit behavior.
Adds compiler, parser, resolver, API, and fourslash coverage.

Reviewed changes

Copilot reviewed 161 out of 167 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
`tsc/internal/ast/*`	Adds source-phase syntax kinds and AST helpers.
`tsc/internal/api/encoder/*`	Encodes and decodes the new phase modifier.
`tsc/internal/checker/*`	Checks syntax and assigns source-module types.
`tsc/internal/compiler/*`	Tracks phase-aware resolutions and Wasm inputs.
`tsc/internal/core/compileroptions.go`	Defines supported module modes.
`tsc/internal/diagnostics/*`	Adds source-import diagnostics.
`tsc/internal/fourslash/tests/sourcePhase`	Tests completions, auto-imports, and organization.
`tsc/internal/ls/*`	Integrates source imports with language services.
`tsc/internal/module/*`	Implements phase-aware module resolution and caching.
`tsc/internal/parser/*`	Parses static and dynamic source imports.
`tsc/internal/scanner/*`	Recognizes `source` as a contextual keyword.
`tsc/internal/testutil/tsbaseline/js_emit_baseline.go`	Includes Wasm files during declaration verification.
`tsc/internal/transformers/moduletransforms/commonjsmodule.go`	Avoids rewriting `import.source()` as ordinary dynamic import.
`tsc/internal/tspath/extension.go`	Adds the Wasm extension.
`tools/scripts/tsc/ast.json`	Updates AST generation metadata.
`packages/typescript/src/*`	Exposes the new syntax through the TypeScript API.
`tsc/testdata/tests/cases/conformance/importSource/*`	Covers syntax, typing, resolution, emit, and errors.
`tsc/testdata/baselines/reference/conformance/importSource*`	Records expected compiler output.
`tsc/testdata/baselines/reference/conformance/importMetaPropertyInvalidInCall.errors.txt`	Updates import meta-property suggestions.

Files not reviewed (6)

tsc/internal/api/encoder/decoder_generated.go: Generated file
tsc/internal/api/encoder/encoder_generated.go: Generated file
tsc/internal/ast/ast_generated.go: Generated file
tsc/internal/ast/kind_generated.go: Generated file
tsc/internal/ast/kind_stringer_generated.go: Generated file
tsc/internal/diagnostics/diagnostics_generated.go: Generated file

Copilot

Pull request overview

Copilot reviewed 169 out of 175 changed files in this pull request and generated 1 comment.

Files not reviewed (6)

tsc/internal/api/encoder/decoder_generated.go: Generated file
tsc/internal/api/encoder/encoder_generated.go: Generated file
tsc/internal/ast/ast_generated.go: Generated file
tsc/internal/ast/kind_generated.go: Generated file
tsc/internal/ast/kind_stringer_generated.go: Generated file
tsc/internal/diagnostics/diagnostics_generated.go: Generated file

Suppressed comments (1)

tsc/internal/fourslash/tests/organizeImports_sourcePhase_test.go:44

This second use has the same compile error: CodeActionKindSourceSortImports is undefined. Use the TypeScript-specific CodeActionKindSourceSortImportsTs constant so the fourslash test package builds.

		lsproto.CodeActionKindSourceSortImports,

Copilot

Pull request overview

Copilot reviewed 169 out of 175 changed files in this pull request and generated no new comments.

Files not reviewed (6)

tsc/internal/api/encoder/decoder_generated.go: Generated file
tsc/internal/api/encoder/encoder_generated.go: Generated file
tsc/internal/ast/ast_generated.go: Generated file
tsc/internal/ast/kind_generated.go: Generated file
tsc/internal/ast/kind_stringer_generated.go: Generated file
tsc/internal/diagnostics/diagnostics_generated.go: Generated file

Copilot

🔵 Needs a closer look

The compiler-wide syntax and resolution changes require final human validation despite comprehensive coverage.

Review details

Files not reviewed (6)

tsc/internal/api/encoder/decoder_generated.go: Generated file
tsc/internal/api/encoder/encoder_generated.go: Generated file
tsc/internal/ast/ast_generated.go: Generated file
tsc/internal/ast/kind_generated.go: Generated file
tsc/internal/ast/kind_stringer_generated.go: Generated file
tsc/internal/diagnostics/diagnostics_generated.go: Generated file

Files reviewed: 169/175 changed files
Comments generated: 0 new
Review effort level: Balanced

Copilot

Copilot review overview

🟡 Changes recommended

Custom module resolvers discard the import phase and cannot resolve mixed evaluation and source imports correctly.

Get a fresh assessment by requesting another Copilot review.

Review effort: Balanced
Findings: 1

Open (1)

Preserve import phase in custom resolver callbacks · New

Files not reviewed (6)

tsc/internal/api/encoder/decoder_generated.go: Generated file
tsc/internal/api/encoder/encoder_generated.go: Generated file
tsc/internal/api/enum_values_generated.go: Generated file
tsc/internal/ast/ast_generated.go: Generated file
tsc/internal/ast/kind_generated.go: Generated file
tsc/internal/ast/kind_stringer_generated.go: Generated file

Copilot

Copilot review overview

🔵 Needs a closer look

It changes parser, checker, resolver, emitter, language-service, and public API contracts across a broad new language feature.

Review effort: Balanced
Findings: None

Resolved since last review (1)

Preserve import phase in custom resolver callbacks

Files not reviewed (6)

tsc/internal/api/encoder/decoder_generated.go: Generated file
tsc/internal/api/encoder/encoder_generated.go: Generated file
tsc/internal/api/enum_values_generated.go: Generated file
tsc/internal/ast/ast_generated.go: Generated file
tsc/internal/ast/kind_generated.go: Generated file
tsc/internal/ast/kind_stringer_generated.go: Generated file

Copilot

Copilot review overview

🟡 Changes recommended

Language-service reference tracking currently conflates source-phase bindings with default imports.

Get a fresh assessment by requesting another Copilot review.

Review effort: Balanced
Findings: 1

Open (1)

Exclude import source bindings from default-export reference tracking · New

Files not reviewed (6)

tsc/internal/api/encoder/decoder_generated.go: Generated file
tsc/internal/api/encoder/encoder_generated.go: Generated file
tsc/internal/api/enum_values_generated.go: Generated file
tsc/internal/ast/ast_generated.go: Generated file
tsc/internal/ast/kind_generated.go: Generated file
tsc/internal/ast/kind_stringer_generated.go: Generated file

Copilot

Copilot review overview

🟡 Changes recommended

API-provided Wasm resolutions can bypass source-phase handling because their extension is not recognized.

Get a fresh assessment by requesting another Copilot review.

Review effort: Balanced
Findings: 1 · 1

Open (2)

Recognize .wasm extensions in static module resolution · New
Exclude import source bindings from default-export reference tracking

Files not reviewed (6)

tsc/internal/api/encoder/decoder_generated.go: Generated file
tsc/internal/api/encoder/encoder_generated.go: Generated file
tsc/internal/api/enum_values_generated.go: Generated file
tsc/internal/ast/ast_generated.go: Generated file
tsc/internal/ast/kind_generated.go: Generated file
tsc/internal/ast/kind_stringer_generated.go: Generated file

Copilot

Copilot review overview

🔵 Needs a closer look

Declaration-file detection incorrectly rejects valid Wasm exports from bare package names ending in .d.ts.

Review effort: Balanced
Findings: 1

Open (1)

Exclude import source bindings from default-export reference tracking

Resolved since last review (1)

Recognize .wasm extensions in static module resolution

Files not reviewed (6)

tsc/internal/api/encoder/decoder_generated.go: Generated file
tsc/internal/api/encoder/encoder_generated.go: Generated file
tsc/internal/api/enum_values_generated.go: Generated file
tsc/internal/ast/ast_generated.go: Generated file
tsc/internal/ast/kind_generated.go: Generated file
tsc/internal/ast/kind_stringer_generated.go: Generated file

Previously missed (1)

In code that hasn't changed since last review

Validate resolved target before rejecting declaration-file imports

tsc/internal/checker/checker.go:14857

This tests the module specifier text rather than the resolved file. A valid bare package such as import source m from "foo.d.ts" can export a .wasm file, but IsDeclarationFileName("foo.d.ts") makes the import an error even though no declaration file was imported. Require the resolved target to be a declaration too before issuing this diagnostic.

Copilot

Copilot review overview

🟡 Changes recommended

Declaration-only package targets are accepted as source imports, and organize-imports uses the wrong comparer for source bindings.

Get a fresh assessment by requesting another Copilot review.

Review effort: Balanced
Findings: 2

Open (2)

Reject direct runtime resolution to declaration-only .d.ts files · New
Exclude import source bindings from default-export reference tracking

Files not reviewed (6)

tsc/internal/api/encoder/decoder_generated.go: Generated file
tsc/internal/api/encoder/encoder_generated.go: Generated file
tsc/internal/api/enum_values_generated.go: Generated file
tsc/internal/ast/ast_generated.go: Generated file
tsc/internal/ast/kind_generated.go: Generated file
tsc/internal/ast/kind_stringer_generated.go: Generated file

Previously missed (1)

In code that hasn't changed since last review

Use named-import comparer when sorting local bindings

tsc/internal/ls/organizeimports.go:488

This sorts local bindings with the module-specifier comparer. In auto mode, module-specifier and named-import casing/order are detected independently, so source bindings can be ordered differently from the file's identifier convention. Pass the named-import comparer for these names instead (the explicit sort test does not expose this because both comparers are identical there).

Copilot

Copilot review overview

🔵 Needs a closer look

The cross-cutting parser, resolver, checker, language-service, and public-protocol changes warrant final human validation despite extensive coverage.

Review effort: Balanced
Findings: 1

Open (1)

Exclude import source bindings from default-export reference tracking

Resolved since last review (1)

Reject direct runtime resolution to declaration-only .d.ts files

Files not reviewed (6)

tsc/internal/api/encoder/decoder_generated.go: Generated file
tsc/internal/api/encoder/encoder_generated.go: Generated file
tsc/internal/api/enum_values_generated.go: Generated file
tsc/internal/ast/ast_generated.go: Generated file
tsc/internal/ast/kind_generated.go: Generated file
tsc/internal/ast/kind_stringer_generated.go: Generated file

Copilot

Copilot review overview

🔵 Needs a closer look

The change spans parser, checker, resolver, emit, language service, and public API behavior and warrants final human validation.

Review effort: Balanced
Findings: None

Resolved since last review (1)

Exclude import source bindings from default-export reference tracking

Files not reviewed (6)

tsc/internal/api/encoder/decoder_generated.go: Generated file
tsc/internal/api/encoder/encoder_generated.go: Generated file
tsc/internal/api/enum_values_generated.go: Generated file
tsc/internal/ast/ast_generated.go: Generated file
tsc/internal/ast/kind_generated.go: Generated file
tsc/internal/ast/kind_stringer_generated.go: Generated file

Copilot

Copilot review overview

🔵 Needs a closer look

It introduces cross-cutting language syntax and resolution semantics requiring final human validation against the TC39 proposal.

Review effort: Balanced
Findings: None

Files not reviewed (8)

tsc/internal/api/encoder/decoder_generated.go: Generated file
tsc/internal/api/encoder/encoder_generated.go: Generated file
tsc/internal/api/enum_values_generated.go: Generated file
tsc/internal/ast/ast_generated.go: Generated file
tsc/internal/ast/kind_generated.go: Generated file
tsc/internal/ast/kind_stringer_generated.go: Generated file
tsc/internal/bundled/embed_generated.go: Generated file
tsc/internal/bundled/libs_generated.go: Generated file

…eat/61216

Ryan Cavanaugh (RyanCavanaugh)

Didn't get a chance to look through everything yet but noticed this so far

Ryan Cavanaugh (RyanCavanaugh) · 2026-09-30T19:12:16Z

+    },
+    "A source phase import must specify a local binding.": {
+        "category": "Error",
+        "code": 100069


Promote to real diagnostic code numbers 😉

…into feat/61216

Copilot AI balanced review requested due to automatic review settings August 20, 2026 13:37

github-project-automation Bot added this to PR Backlog Aug 20, 2026

github-project-automation Bot moved this to Not started in PR Backlog Aug 20, 2026

typescript-automation Bot added For Milestone Bug PRs that fix a bug with a specific milestone labels Aug 20, 2026

Copilot started reviewing on behalf of Oleksandr Tarasiuk (a-tarasyuk) August 20, 2026 13:46 View session

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Comment thread tsc/testdata/baselines/reference/conformance/importSource9.js Outdated

Oleksandr Tarasiuk (a-tarasyuk) force-pushed the feat/61216 branch 4 times, most recently from 1651b1d to 6b93ada Compare August 24, 2026 16:43

Oleksandr Tarasiuk (a-tarasyuk) requested a balanced review from Copilot August 27, 2026 14:41

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Comment thread tsc/internal/fourslash/tests/organizeImports_sourcePhase_test.go Outdated

Oleksandr Tarasiuk (a-tarasyuk) requested a balanced review from Copilot August 27, 2026 14:53

Copilot started reviewing on behalf of Oleksandr Tarasiuk (a-tarasyuk) August 27, 2026 14:55 View session

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Oleksandr Tarasiuk (a-tarasyuk) requested a balanced review from Copilot September 8, 2026 07:09

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Oleksandr Tarasiuk (a-tarasyuk) requested a balanced review from Copilot September 25, 2026 10:17

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