support quick info and go to definition on mapped keys by Zzzen · Pull Request #3264 · microsoft/typescript-go

Zzzen · 2026-03-27T14:26:53Z

Fixes microsoft/TypeScript#50715
Fixes microsoft/TypeScript#56019
Fixes microsoft/TypeScript#61094

Fixes:

Mapped keys do not preserve JSDoc documentation TypeScript#50715
regression in "key remapping breaks definition navigation" TypeScript#56019
[TypeScript] Mapped Types with Template Literal Keys Do Not Preserve Type Declaration References TypeScript#61094

This was originally implemented in microsoft/TypeScript#61061 (migrated here).

Copilot

Pull request overview

Adds language service support for Quick Info (hover) and Go to Definition on mapped type properties, including cases where keys are remapped (e.g. via as), aligning behavior with upstream TypeScript fixes for the linked issues.

Changes:

Attach and surface JSDoc (notably @inheritDoc) on MappedTypeNode so hover can show documentation for remapped mapped properties.
Improve go-to-definition for mapped properties by falling back to the mapped symbol’s syntheticOrigin declarations when the mapped property has no direct declarations.
Add fourslash coverage + reference baselines for hover and go-to-definition on mapped keys.

Reviewed changes

Copilot reviewed 14 out of 14 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
internal/parser/utilities.go	Includes `KindMappedType` in JSDoc comment range collection so mapped types can have lazily-parsed JSDoc in TS/TSX.
internal/parser/parser.go	Records preceding JSDoc info when parsing mapped types and attaches it via `withJSDoc`.
internal/checker/checker.go	Sets `prop.Parent` for mapped properties to the mapped type symbol to enable doc lookup via parent declarations.
internal/checker/services.go	Exposes `GetMappedSyntheticOrigin` helper for LS to navigate mapped symbols back to their source property symbol.
internal/ls/hover.go	Synthesizes hover documentation for mapped properties (when declaration is nil) using mapped type + synthetic origin declarations when `@inheritDoc` is present.
internal/ls/definition.go	Adds go-to-definition fallback to synthetic origin declarations for mapped properties with no declarations.
internal/fourslash/tests/quickInfoMappedType2_test.go	Adds/updates quick info fourslash coverage for mapped type `@inheritDoc` hover.
internal/fourslash/tests/quickInfoMappedType3_test.go	Adds hover baseline test for mapped type remapped keys showing inherited doc text.
internal/fourslash/tests/quickInfoMappedType4_test.go	Adds a quick info regression test for a different `@inheritDoc` placement scenario.
internal/fourslash/tests/goToDefinitionMappedType2_test.go	Adds go-to-definition fourslash test for mapped keys with remapping.
internal/fourslash/tests/goToDefinitionMappedType3_test.go	Adds go-to-definition fourslash test for mapped keys transformed with a suffix.
testdata/baselines/reference/fourslash/quickInfo/quickInfoMappedType3.baseline	New reference baseline for hover output on mapped properties.
testdata/baselines/reference/fourslash/goToDefinition/goToDefinitionMappedType2.baseline.jsonc	New reference baseline for go-to-definition on remapped mapped keys.
testdata/baselines/reference/fourslash/goToDefinition/goToDefinitionMappedType3.baseline.jsonc	New reference baseline for go-to-definition on suffix-transformed keys.

Comments suppressed due to low confidence (1)

internal/fourslash/tests/quickInfoMappedType3_test.go:54

Same as above: this comment says hover docs are not displayed, but the updated baseline indicates documentation is shown. Please update the marker comment to match expected behavior.

// ❌ When hovering here, the documentation is NOT displayed.
me./*4*/getName();`

Copilot · 2026-03-31T18:41:27Z

+  // ❌ When hovering here, the documentation is NOT displayed.
+  /*1*/getName: () => "Jake Carter",
+  // ❌ When hovering here, the documentation is NOT displayed.
+  /*2*/getAge: () => 35,
+  // ❌ When hovering here, the documentation is NOT displayed.
+  /*3*/getLocation: () => "United States",
+};
+
+// ❌ When hovering here, the documentation is NOT displayed.


The embedded test source still says hover documentation is not displayed for the mapped properties/call sites, but the baseline now shows documentation coming from the mapped type's @inheritdoc. Please update these ❌ comments to match the new expected behavior to avoid confusing future test readers.

This issue also appears on line 53 of the same file.

Suggested change

// ❌ When hovering here, the documentation is NOT displayed.

/*1*/getName: () => "Jake Carter",

// ❌ When hovering here, the documentation is NOT displayed.

/*2*/getAge: () => 35,

// ❌ When hovering here, the documentation is NOT displayed.

/*3*/getLocation: () => "United States",

};

// ❌ When hovering here, the documentation is NOT displayed.

// ✅ When hovering here, the documentation is displayed, as it should.

/*1*/getName: () => "Jake Carter",

// ✅ When hovering here, the documentation is displayed, as it should.

/*2*/getAge: () => 35,

// ✅ When hovering here, the documentation is displayed, as it should.

/*3*/getLocation: () => "United States",

};

// ✅ When hovering here, the documentation is displayed, as it should.

Actually we should not have comments because they were purely for the repo maintainers. Just drop these.

Updated. PTAL when you have a chance. Thanks!

Copilot · 2026-03-31T18:41:28Z

+    d: string;
+}
+
+type T50 = Getters<Y>;  // { getFoo: () => string, getBar: () => number }


This comment appears to be copy/pasted and doesn't match the test input (Y only has d, so the mapped type should produce getD). Consider correcting or removing it to keep the test self-explanatory.

Suggested change

type T50 = Getters<Y>; // { getFoo: () => string, getBar: () => number }

type T50 = Getters<Y>; // { getD: () => string }

Just remove the comments. They are lossy artifacts.

Copilot · 2026-03-31T18:41:28Z

+    d: string;
+}
+
+type T50 = Getters<Y>;  // { getFoo: () => string, getBar: () => number }


This comment doesn't match the test input (Y only has d, so the resulting mapped property should be getD). Please correct or remove to avoid misleading documentation in the test case.

Suggested change

type T50 = Getters<Y>; // { getFoo: () => string, getBar: () => number }

type T50 = Getters<Y>; // { getD: () => string }

Copilot · 2026-03-31T18:41:28Z

+		// For mapped type symbols with @inheritDoc on the mapped type, synthesize documentation
+		// from the mapped type's declarations and the syntheticOrigin's declarations.


The comment says documentation is "synthesized from" mapped type + syntheticOrigin declarations, but the implementation actually returns documentation from the first declaration in the combined list that produces non-empty output. Consider updating the comment (or changing the logic) so the behavior and documentation are consistent.

Suggested change

// For mapped type symbols with @inheritDoc on the mapped type, synthesize documentation

// from the mapped type's declarations and the syntheticOrigin's declarations.

// For mapped type symbols with @inheritDoc on the mapped type, collect documentation

// by considering the mapped type's declarations and the syntheticOrigin's declarations.

Copilot

Pull request overview

Copilot reviewed 14 out of 14 changed files in this pull request and generated 1 comment.

Copilot · 2026-04-16T21:32:10Z

+};
+
+interface Person {
+  // ✅ When hovering here, the documentation is displayed, as it should.


The embedded TS test source still includes the "✅ When hovering here..." narration (and the ✅ symbol). Per earlier reviewer guidance, please remove these explanatory comments from the content string (and the other similar occurrences in this test) to avoid lossy/noisy artifacts in baselines and keep the test focused on markers/baseline output.

geekeren · 2026-05-23T02:46:31Z

do we have any beta version to validate?

gabritto

The approach looks ok to me, but I have some questions/concerns, especially around @inheritDoc.

gabritto · 2026-05-26T15:24:44Z

+
+{
+    let gotoDef!: JustMapIt<Foo>
+    gotoDef.property


Did you mean to also test the simpler case here?

gabritto · 2026-05-26T16:07:50Z

+	f, done := fourslash.NewFourslash(t, nil /*capabilities*/, content)
+	defer done()
+	// Current Go behavior: shows the raw @inheritDoc tag text from the mapped type declaration.
+	f.VerifyQuickInfoAt(t, "3", "(property) getD: () => string", "\n\n*@inheritDoc* \u2014 desc on Getters ")


So the default behavior will be to not inherit the jsdoc from e.g. Y, unless @inheritDoc is present in the mapped type?
Also, this shouldn't affect "go to definition", right? Only documentation.

I'm wondering if it makes sense to also port @inheritDoc support in this PR then, since otherwise you can't inherit the docs.

gabritto · 2026-05-26T16:22:53Z

+	defer testutil.RecoverAndFail(t, "Panic on fourslash test")
+	const content = `type ToGet<T> = T extends string ? ` + "`get${Capitalize<T>}`" + ` : never;
+type Getters<T> = { 
+    /** @inheritDoc desc on Getters */


Why doesn't this work but adding the comment outside the mapped type work?

gabritto · 2026-05-26T16:59:14Z

+	// TODO: once @inheritDoc resolution is fully implemented, the expected documentation
+	// should be "desc on Getters\nhello" (combined from the mapped type and the source property).
+	const content = `type ToGet<T> = T extends string ? ` + "`get${Capitalize<T>}`" + ` : never;
+type Getters<T> = /** @inheritDoc desc on Getters */ { 


Could you also add a quick info case without property remapping?

support quick info and go to definition on mapped keys

7f7b257

DanielRosenwasser requested a review from Copilot March 31, 2026 18:33

Copilot started reviewing on behalf of DanielRosenwasser March 31, 2026 18:35 View session

Copilot AI reviewed Mar 31, 2026

View reviewed changes

Zzzen added 2 commits April 10, 2026 20:05

fix comments

6ef2c71

update baseline

c252871

jakebailey requested review from DanielRosenwasser and Copilot April 16, 2026 21:27

Copilot started reviewing on behalf of jakebailey April 16, 2026 21:28 View session

Copilot AI reviewed Apr 16, 2026

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RyanCavanaugh assigned gabritto Apr 17, 2026

RyanCavanaugh added this to the TypeScript 7.0 RC milestone Apr 17, 2026

RyanCavanaugh requested a review from gabritto April 17, 2026 17:35

gabritto requested changes May 26, 2026

View reviewed changes

RyanCavanaugh modified the milestones: TypeScript 7.0 RC, Post-7.0 Jun 12, 2026

	type T50 = Getters<Y>; // { getFoo: () => string, getBar: () => number }
	type T50 = Getters<Y>; // { getD: () => string }

		// For mapped type symbols with @inheritDoc on the mapped type, synthesize documentation
		// from the mapped type's declarations and the syntheticOrigin's declarations.

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Zzzen commented Mar 27, 2026 • edited by jakebailey Loading Uh oh! There was an error while loading. Please reload this page.

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Zzzen commented Mar 27, 2026 •

edited by jakebailey

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DanielRosenwasser Mar 31, 2026 •

edited

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