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Preserve primitive literal union origins without special intersections - #64411
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Wesley Wigham (weswigham) wants to merge 7 commits into
Open
Wesley Wigham (weswigham) wants to merge 7 commits into
Wesley Wigham (weswigham) wants to merge 7 commits into
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Reduce string & {}, number & {}, and bigint & {} normally. Preserve redundant literals alongside their matching broad primitive in sparse origin metadata. Use the origins for completions, quick info, and mapped-key enumeration without changing ordinary type printing. Recognize origin-bearing primitive copies in index-signature and union comparisons.
Strada history:
- microsoft#28429 first allowed string & {} to survive by preserving actual empty object intersections.
microsoft#28429
- microsoft#49119 introduced noSupertypeReduction for string, number, and bigint intersections, explicitly documenting and testing the completion exception in completionPreferredSuggestions1.ts.
microsoft#49119
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Wesley Wigham (weswigham)
September 23, 2026 20:39
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🔵 Needs a closer look
Origin metadata is still lost during control-flow filtering and nested union composition, producing incomplete completions and quick info.
Review effort: Balanced
Findings: None
What changed in this PR
Preserves primitive literal union origins for completions, quick info, and mapped keys while normally reducing legacy primitive intersections.
Changes:
- Adds reduced-union origin metadata.
- Updates language-service consumers.
- Expands compiler and fourslash coverage.
| File | Reviewed change |
|---|---|
tsc/testdata/tests/cases/compiler/templateLiteralOriginReduction.ts |
Tests template-literal origin reduction. |
tsc/testdata/tests/cases/compiler/stringOriginIndexSignatures.ts |
Tests string-origin index signatures. |
tsc/testdata/tests/cases/compiler/numericLiteralOrigins.ts |
Tests numeric and bigint origins. |
tsc/testdata/tests/cases/compiler/mappedStringLiteralOrigin.ts |
Tests mapped string-literal origins. |
tsc/testdata/tests/cases/compiler/emptyObjectIntersectionReduction.ts |
Tests empty-object intersection reduction. |
tsc/testdata/baselines/reference/fourslash/quickInfo/quickInfoStringLiteralOrigin_plaintext.baseline |
Records plaintext quick-info output. |
tsc/testdata/baselines/reference/fourslash/quickInfo/quickInfoStringLiteralOrigin_markdown.baseline |
Records Markdown quick-info output. |
tsc/testdata/baselines/reference/conformance/unknownControlFlow.types |
Updates control-flow type baselines. |
tsc/testdata/baselines/reference/conformance/templateLiteralTypesPatterns.types |
Updates template-pattern type baselines. |
tsc/testdata/baselines/reference/conformance/templateLiteralTypes2.types |
Updates template-literal type baselines. |
tsc/testdata/baselines/reference/conformance/stringMappingReduction.types |
Updates string-mapping reduction baselines. |
tsc/testdata/baselines/reference/compiler/templateLiteralOriginReduction.types |
Records template-origin types. |
tsc/testdata/baselines/reference/compiler/templateLiteralOriginReduction.symbols |
Records template-origin symbols. |
tsc/testdata/baselines/reference/compiler/templateLiteralOriginReduction.js |
Records template-origin emit. |
tsc/testdata/baselines/reference/compiler/templateLiteralOriginReduction.errors.txt |
Records template-origin diagnostics. |
tsc/testdata/baselines/reference/compiler/stringOriginIndexSignatures(nouncheckedindexedaccess=true).types |
Records checked index-signature types. |
tsc/testdata/baselines/reference/compiler/stringOriginIndexSignatures(nouncheckedindexedaccess=true).symbols |
Records checked index-signature symbols. |
tsc/testdata/baselines/reference/compiler/stringOriginIndexSignatures(nouncheckedindexedaccess=true).js |
Records checked index-signature emit. |
tsc/testdata/baselines/reference/compiler/stringOriginIndexSignatures(nouncheckedindexedaccess=true).errors.txt |
Records checked index-signature diagnostics. |
tsc/testdata/baselines/reference/compiler/stringOriginIndexSignatures(nouncheckedindexedaccess=false).types |
Records unchecked index-signature types. |
tsc/testdata/baselines/reference/compiler/stringOriginIndexSignatures(nouncheckedindexedaccess=false).symbols |
Records unchecked index-signature symbols. |
tsc/testdata/baselines/reference/compiler/stringOriginIndexSignatures(nouncheckedindexedaccess=false).js |
Records unchecked index-signature emit. |
tsc/testdata/baselines/reference/compiler/stringOriginIndexSignatures(nouncheckedindexedaccess=false).errors.txt |
Records unchecked index-signature diagnostics. |
tsc/testdata/baselines/reference/compiler/specialIntersectionsInMappedTypes.types |
Updates mapped-intersection types. |
tsc/testdata/baselines/reference/compiler/numericLiteralOrigins.types |
Records numeric-origin types. |
tsc/testdata/baselines/reference/compiler/numericLiteralOrigins.symbols |
Records numeric-origin symbols. |
tsc/testdata/baselines/reference/compiler/numericLiteralOrigins.js |
Records numeric-origin emit. |
tsc/testdata/baselines/reference/compiler/numericLiteralOrigins.errors.txt |
Records numeric-origin diagnostics. |
tsc/testdata/baselines/reference/compiler/nestedGenericTypeInference.types |
Updates generic-inference types. |
tsc/testdata/baselines/reference/compiler/mappedStringLiteralOrigin(exactoptionalpropertytypes=true).types |
Records exact-optional mapped types. |
tsc/testdata/baselines/reference/compiler/mappedStringLiteralOrigin(exactoptionalpropertytypes=true).symbols |
Records exact-optional mapped symbols. |
tsc/testdata/baselines/reference/compiler/mappedStringLiteralOrigin(exactoptionalpropertytypes=true).js |
Records exact-optional mapped emit. |
tsc/testdata/baselines/reference/compiler/mappedStringLiteralOrigin(exactoptionalpropertytypes=true).errors.txt |
Records exact-optional mapped diagnostics. |
tsc/testdata/baselines/reference/compiler/mappedStringLiteralOrigin(exactoptionalpropertytypes=false).types |
Records standard mapped types. |
tsc/testdata/baselines/reference/compiler/mappedStringLiteralOrigin(exactoptionalpropertytypes=false).symbols |
Records standard mapped symbols. |
tsc/testdata/baselines/reference/compiler/mappedStringLiteralOrigin(exactoptionalpropertytypes=false).js |
Records standard mapped emit. |
tsc/testdata/baselines/reference/compiler/mappedStringLiteralOrigin(exactoptionalpropertytypes=false).errors.txt |
Records standard mapped diagnostics. |
tsc/testdata/baselines/reference/compiler/emptyObjectIntersectionReduction(strictnullchecks=true).types |
Records strict-null intersection types. |
tsc/testdata/baselines/reference/compiler/emptyObjectIntersectionReduction(strictnullchecks=true).symbols |
Records strict-null intersection symbols. |
tsc/testdata/baselines/reference/compiler/emptyObjectIntersectionReduction(strictnullchecks=true).js |
Records strict-null intersection emit. |
tsc/testdata/baselines/reference/compiler/emptyObjectIntersectionReduction(strictnullchecks=false).types |
Records non-strict intersection types. |
tsc/testdata/baselines/reference/compiler/emptyObjectIntersectionReduction(strictnullchecks=false).symbols |
Records non-strict intersection symbols. |
tsc/testdata/baselines/reference/compiler/emptyObjectIntersectionReduction(strictnullchecks=false).js |
Records non-strict intersection emit. |
tsc/internal/ls/string_completions.go |
Traverses origins for string completions. |
tsc/internal/ls/hover.go |
Uses origins in quick info. |
tsc/internal/ls/completions.go |
Uses literal origins for completions. |
tsc/internal/fourslash/tests/templateLiteralOriginCompletions_test.go |
Tests template-literal completions. |
tsc/internal/fourslash/tests/stringLiteralCompletionsFromReducedUnion_test.go |
Tests reduced string-union completions. |
tsc/internal/fourslash/tests/specialIntersectionsOrderIndependent_test.go |
Tests intersection order independence. |
tsc/internal/fourslash/tests/reducedOriginInstantiation_test.go |
Tests instantiated origins. |
tsc/internal/fourslash/tests/quickInfoStringLiteralOrigin_test.go |
Tests string-origin quick info. |
tsc/internal/fourslash/tests/quickInfoNumericLiteralOrigin_test.go |
Tests numeric-origin quick info. |
tsc/internal/fourslash/tests/numericLiteralCompletionsFromReducedUnion_test.go |
Tests reduced numeric-union completions. |
tsc/internal/checker/types.go |
Defines reduced-type origin links. |
tsc/internal/checker/relater.go |
Updates origin-bearing type relationships. |
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Well yeah, intentionally. Control flow will happily narrow to a non-origin'd version of the type, at which point the info is gone (ofc), likewise with quick info. Quickinfo is also only displayed on types that are exactly a type with an origin - a type with an origin embedded within another type (union, object, intersection, conditional, whatever), doesn't display any differently than the base type it aliases (though I can see a world where we use expandable hover and some kind of hint decoration to allow expanding to see the origin in those cases, it's not in this PR). |
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TypeScript Bot (@typescript-bot) test it |
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Jake Bailey (@jakebailey) Here they are:
tscComparison Report - baseline..pr
System info unknown
Hosts
Scenarios
Developer Information: |
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Hey Jake Bailey (@jakebailey), it looks like the DT test run failed. Please check the log for more details. |
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The DT hang might be real? It's taking much longer? |
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Multiple of the top / user tests are also hitting that. |
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I'll look into it before I remove the compat mapped type behavior and simplify the quickinfo to just the origin type. |
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Looks like just a reentrancy bug in the mapped type logic, which is going away anyway, simple fix then. |
| === stringMappingReduction.ts === | ||
| type T00 = "prop" | `p${Lowercase<string>}p`; // `p${Lowercase<string>}p` | ||
| >T00 : `p${Lowercase<string>}p` | ||
| >T00 : T00 |
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Odd how this turns into a self naming
| function C2(transform: "-moz-initial" | (string & {})) { return 12; } | ||
| >C2 : (transform: "-moz-initial" | (string & {})) => number | ||
| >transform : "-moz-initial" | (string & {}) | ||
| >transform : string |
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I assume this is happening because only hover shows the nice type, whereas the baselines show the real one
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Correct - would you rather we show more details in .types? I can change it to print both, if we'd like.
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Given the choice was to drop the special printing, I'm not sure it matters
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Well, the choice was to print quickinfo as the origin type, meanwhile the baselines are still showing the actual type, so they do disagree. Imma make .types show both - no reason they can't be explicit.
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TypeScript Bot (@typescript-bot) test it |
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Hey Wesley Wigham (@weswigham), the results of running the DT tests are ready. There were interesting changes: Branch only errors:Package: Branch error: Project scope: Error: /mnt/vss/_work/1/s/DefinitelyTyped/types/oojs-ui/oojs-ui-tests.ts:2426:5 TypeScript@local expected type to be: Record<string, Icon> got: Record<string, string> /mnt/vss/_work/1/s/DefinitelyTyped/types/oojs-ui/oojs-ui-tests.ts:2850:13 TypeScript@local expected type to be: Icon | Record<string, Icon> | undefined got: string | Record<string, string> | undefined at combineErrorsAndWarnings (/mnt/vss/_work/1/s/DefinitelyTyped-tools/packages/dtslint/dist/index.js:204:28) at runTests (/mnt/vss/_work/1/s/DefinitelyTyped-tools/packages/dtslint/dist/index.js:196:20) Branch only errors:Package: Branch error: Project scope: Error: /mnt/vss/_work/1/s/DefinitelyTyped/types/react/test/tsx.tsx:936:9
TypeScript@local compile error TS2578:
Unused '@ts-expect-error' directive.
at combineErrorsAndWarnings (/mnt/vss/_work/1/s/DefinitelyTyped-tools/packages/dtslint/dist/index.js:204:28)
at runTests (/mnt/vss/_work/1/s/DefinitelyTyped-tools/packages/dtslint/dist/index.js:196:20)
Branch only errors:Package: Branch error: Project scope: Error: /mnt/vss/_work/1/s/DefinitelyTyped/types/leaflet-pixi-overlay/leaflet-pixi-overlay-tests.ts:21:39
TypeScript@local compile error TS2345:
Argument of type 'Graphics' is not assignable to parameter of type 'DisplayObject'.
Types of property 'children' are incompatible.
Type 'DisplayObject[]' is not assignable to type 'readonly FederatedEventTarget[]'.
Type 'DisplayObject' is not assignable to type 'FederatedEventTarget'.
The types of 'parent.eventNames()' are incompatible between these types.
Type '(keyof DisplayObjectEvents)[]' is not assignable to type '(string | symbol)[]'.
Type 'keyof DisplayObjectEvents' is not assignable to type 'string | symbol'.
Type 'number' is not assignable to type 'string | symbol'.
at combineErrorsAndWarnings (/mnt/vss/_work/1/s/DefinitelyTyped-tools/packages/dtslint/dist/index.js:204:28)
at runTests (/mnt/vss/_work/1/s/DefinitelyTyped-tools/packages/dtslint/dist/index.js:196:20)
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Member
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RE: DT, if this is exposed over the API, theoretically I can make it prefer the new string, I think? The other failures are interesting, though. |
Contributor
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Wesley Wigham (@weswigham) Here are the results of running the user tests with tsc comparing Everything looks good! |
Contributor
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Wesley Wigham (@weswigham) Here they are:
tscComparison Report - baseline..pr
System info unknown
Hosts
Scenarios
Developer Information: |
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Contributor
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Wesley Wigham (@weswigham) Here are the results of running the top 400 repos with tsc comparing Something interesting changed - please have a look. Details
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And reduce string & {}, number & {}, and bigint & {} normally. This preserves redundant literals alongside their matching broad primitive in an "origin" checker link. These origins are used for completions, quick info, and mapped-key enumeration without changing ordinary type printing (for compatibility with the old
& {}patterns - I think these origins affecting mapped type keys is odd, but I understand the usefulness, at least)Strada history:
Ultimately, this PR gives you an editor experience like this:
Recording.2026-09-23.133101.mp4
Without needing to opt into a weird
string & {}pattern that triggers a bunch of normalization exceptions through the checker. Note the specialized origin-retaining quickinfo that can print the full union origin of thestringtype, and the now-functional string literal completions in a case where before we did not have them (without writingstring & {}instead ofstringto opt in to a denormalized union).