Negated Types: Change the meaning of `{}` to `unknown & not null & not undefined` by weswigham · Pull Request #64376 · microsoft/TypeScript

Wesley Wigham (weswigham) · 2026-09-21T17:52:31Z

This PR stacks on top of #64375.

In this PR, we drop the unknown = {} | null | undefined equivalence we use in a few places, and instead choose to interpret {} as unknown & not null & not undefined. In doing so, I had to choose to either persist our special behaviors for literal unions with base & {} as non-simplifying, or replace it. I chose to eliminate that, and instead broadened our existing type-origin machinery to be able to apply to clones of string/number/bigint, so you can have a string that comes from "a" | "b" | string, which shows that origin in quickinfo and uses it for completions (...and mapped type construction, which feels wrong, but is what we needed for compat with the old way). An alternative would be a new carve-out that recognized the new negated types to disable normalization, but that feels.... weird. I think handling the origin information in a first-class way ends up working a bit more nicely than allowing (some) denormalized unions outside of .origins, conceptually.

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: - #28429 first allowed string & {} to survive by preserving actual empty object intersections. #28429 - #49119 introduced noSupertypeReduction for string, number, and bigint intersections, explicitly documenting and testing the completion exception in completionPreferredSuggestions1.ts. #49119

Represent {} under strictNullChecks as unknown & not null & not undefined. Remove the synthetic unknown union, recombination helpers, and unknown-like union assignability special case. Narrow nullish types directly through intersections and exclusions. Replace the {} | null | undefined formulation introduced by #49119 while preserving apparent members, empty-type identity, and generic indexed access. #49119

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🟡 Changes recommended

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What changed in this PR

Adds negated types (not T) and redefines {} as non-nullish unknown across the compiler, language services, APIs, and tests.

Changes:

Implements negated-type parsing, normalization, inference, narrowing, and emit.
Preserves literal origins for hover and completions.
Updates public APIs and extensive compiler baselines.

File	Summary
`tsc/testdata/tests/cases/conformance/types/negated/negatedUnionComplementSimplifies.ts`	Tests union-complement simplification.
`tsc/testdata/tests/cases/conformance/types/negated/negatedTypesSimplifyInIntersections.ts`	Tests intersection simplification.
`tsc/testdata/tests/cases/conformance/types/negated/negatedTypesSatisfiesAndArrays.ts`	Tests arrays and `satisfies`.
`tsc/testdata/tests/cases/conformance/types/negated/negatedTypesNormalizationIdentities.ts`	Tests normalization identities.
`tsc/testdata/tests/cases/conformance/types/negated/negatedTypesInStringMappingAndIndexSignatures.ts`	Tests string mappings and index signatures.
`tsc/testdata/tests/cases/conformance/types/negated/negatedTypesInStringMapping.ts`	Tests string mappings.
`tsc/testdata/tests/cases/conformance/types/negated/negatedTypesInPatternLiteralsStringMappingAndIndexSignatures.ts`	Tests combined pattern-literal behavior.
`tsc/testdata/tests/cases/conformance/types/negated/negatedTypesInPatternLiteralsAndStringMapping.ts`	Tests pattern literals and mappings.
`tsc/testdata/tests/cases/conformance/types/negated/negatedTypesInPatternLiteralsAndIndexSignatures.ts`	Tests pattern-literal index signatures.
`tsc/testdata/tests/cases/conformance/types/negated/negatedTypesInPatternLiterals.ts`	Tests pattern literals.
`tsc/testdata/tests/cases/conformance/types/negated/negatedTypesInKeyofAndMappedKeyRemapping.ts`	Tests `keyof` and key remapping.
`tsc/testdata/tests/cases/conformance/types/negated/negatedTypesInIndexSignatures.ts`	Tests index signatures.
`tsc/testdata/tests/cases/conformance/types/negated/negatedTypesInConditionalTypesAndInfer.ts`	Tests conditional types and inference.
`tsc/testdata/tests/cases/conformance/types/negated/negatedTypesGenericInference.ts`	Tests generic inference.
`tsc/testdata/tests/cases/conformance/types/negated/negatedTypesDeMorgan.ts`	Tests De Morgan identities.
`tsc/testdata/tests/cases/conformance/types/negated/negatedTypesDeclarationEmit.ts`	Tests declaration emit.
`tsc/testdata/tests/cases/conformance/types/negated/negatedTypesControlFlowNarrowing.ts`	Tests control-flow narrowing.
`tsc/testdata/tests/cases/conformance/types/negated/negatedTypesControlFlow.ts`	Tests control-flow behavior.
`tsc/testdata/tests/cases/conformance/types/negated/negatedTypesContextualLiteralTypes.ts`	Tests contextual literals.
`tsc/testdata/tests/cases/conformance/types/negated/negatedTypesComparability.ts`	Tests comparability.
`tsc/testdata/tests/cases/conformance/types/negated/negatedTypeAppliesToFalseBranchOfConditional.ts`	Tests conditional false-branch narrowing.
`tsc/testdata/tests/cases/conformance/types/negated/negatedRepresentativeExamples.ts`	Adds representative examples.
`tsc/testdata/tests/cases/conformance/types/negated/negatedNarrowingTypePredicate.ts`	Tests predicate narrowing.
`tsc/testdata/tests/cases/conformance/types/negated/negatedNarrowingTruthiness.ts`	Tests truthiness narrowing.
`tsc/testdata/tests/cases/conformance/types/negated/negatedNarrowingSwitchTypeof.ts`	Tests `typeof` switch narrowing.
`tsc/testdata/tests/cases/conformance/types/negated/negatedNarrowingSwitchTrue.ts`	Tests `switch (true)` narrowing.
`tsc/testdata/tests/cases/conformance/types/negated/negatedNarrowingInOperator.ts`	Tests `in` narrowing.
`tsc/testdata/tests/cases/conformance/types/negated/negatedNarrowingEqualityLiteral.ts`	Tests literal equality narrowing.
`tsc/testdata/tests/cases/conformance/types/negated/negatedNarrowingEquality.ts`	Tests equality narrowing.
`tsc/testdata/tests/cases/conformance/types/negated/negatedNarrowingAssertion.ts`	Tests assertion narrowing.
`tsc/testdata/tests/cases/conformance/types/negated/negatedInMappedTypeDisablesExcessProperties.ts`	Tests mapped excess-property behavior.
`tsc/testdata/tests/cases/conformance/types/negated/negatedFreshOptionalProperties.ts`	Tests fresh optional properties.
`tsc/testdata/tests/cases/compiler/negatedTypeSmokeTypeof.ts`	Adds `typeof` smoke coverage.
`tsc/testdata/tests/cases/compiler/negatedTypeSmokeNullable.ts`	Adds nullable smoke coverage.
`tsc/testdata/tests/cases/compiler/negatedTypeSmokeInference.ts`	Adds inference smoke coverage.
`tsc/testdata/tests/cases/compiler/negatedRealWorldControlFlowRegressions.ts`	Covers control-flow regressions.
`tsc/testdata/tests/cases/compiler/negatedPartialTypeGuards.ts`	Tests partial type guards.
`tsc/testdata/tests/cases/compiler/negatedNumericEnumComparability.ts`	Tests numeric enum comparability.
`tsc/testdata/tests/cases/compiler/negatedGenericForIn.ts`	Tests generic `for...in`.
`tsc/testdata/tests/cases/compiler/negatedCompoundAssignmentFlow.ts`	Tests compound-assignment flow.
`tsc/testdata/fixtures/compiler/commandLineParser.ts`	Updates compiler fixture typing.
`tsc/testdata/fixtures/compiler/checker.ts`	Updates checker fixture behavior.
`tsc/testdata/baselines/reference/conformance/weakTypesAndLiterals01.js`	Updates emit baseline.
`tsc/testdata/baselines/reference/conformance/unknownType1.types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/unknownControlFlow.js`	Updates emit baseline.
`tsc/testdata/baselines/reference/conformance/undefinedAssignableToEveryType.errors.txt`	Updates diagnostic baseline.
`tsc/testdata/baselines/reference/conformance/TypeGuardWithEnumUnion.types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/thisTypeInFunctions2.types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/thisTypeInFunctions2.symbols`	Updates symbol baseline.
`tsc/testdata/baselines/reference/conformance/templateLiteralTypes2.types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/stringLiteralTypesOverloads02.types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/stringLiteralTypesInUnionTypes02.types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/staticIndexSignature4.types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/spreadObjectOrFalsy.types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/spreadObjectOrFalsy.js`	Updates emit baseline.
`tsc/testdata/baselines/reference/conformance/scannerS7.3_A1.1_T2.types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/scannerS7.2_A1.5_T2.types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/privateNameInInExpression(target=esnext).errors.txt`	Updates diagnostic baseline.
`tsc/testdata/baselines/reference/conformance/privateNameInInExpression(target=es2022).errors.txt`	Updates diagnostic baseline.
`tsc/testdata/baselines/reference/conformance/parserUnicode1.types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/parserS7.3_A1.1_T2.types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/parserS7.2_A1.5_T2.types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/parserharness.types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/nullishCoalescingOperator2.types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/nullishCoalescingOperator_es2020.types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/noInfer.types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/negatedTypesSimplifyInIntersections.types`	Adds type baseline.
`tsc/testdata/baselines/reference/conformance/negatedTypesSimplifyInIntersections.symbols`	Adds symbol baseline.
`tsc/testdata/baselines/reference/conformance/negatedTypesSimplifyInIntersections.js`	Adds emit baseline.
`tsc/testdata/baselines/reference/conformance/negatedTypesNormalizationIdentities.errors.txt`	Adds diagnostic baseline.
`tsc/testdata/baselines/reference/conformance/negatedTypesDeclarationEmit.types`	Adds type baseline.
`tsc/testdata/baselines/reference/conformance/negatedTypesDeclarationEmit.js`	Adds emit baseline.
`tsc/testdata/baselines/reference/conformance/negatedTypesControlFlow.js`	Adds emit baseline.
`tsc/testdata/baselines/reference/conformance/negatedTypesComparability.types`	Adds type baseline.
`tsc/testdata/baselines/reference/conformance/negatedTypesComparability.symbols`	Adds symbol baseline.
`tsc/testdata/baselines/reference/conformance/negatedTypesComparability.errors.txt`	Adds diagnostic baseline.
`tsc/testdata/baselines/reference/conformance/negatedTypeAppliesToFalseBranchOfConditional.types`	Adds type baseline.
`tsc/testdata/baselines/reference/conformance/negatedTypeAppliesToFalseBranchOfConditional.symbols`	Adds symbol baseline.
`tsc/testdata/baselines/reference/conformance/negatedTypeAppliesToFalseBranchOfConditional.js`	Adds emit baseline.
`tsc/testdata/baselines/reference/conformance/negatedTypeAppliesToFalseBranchOfConditional.errors.txt`	Adds diagnostic baseline.
`tsc/testdata/baselines/reference/conformance/negatedNarrowingTypePredicate.errors.txt`	Adds diagnostic baseline.
`tsc/testdata/baselines/reference/conformance/negatedNarrowingTruthiness.types`	Adds type baseline.
`tsc/testdata/baselines/reference/conformance/negatedNarrowingInOperator.errors.txt`	Adds diagnostic baseline.
`tsc/testdata/baselines/reference/conformance/negatedInMappedTypeDisablesExcessProperties.types`	Adds type baseline.
`tsc/testdata/baselines/reference/conformance/negatedInMappedTypeDisablesExcessProperties.js`	Adds emit baseline.
`tsc/testdata/baselines/reference/conformance/negatedInMappedTypeDisablesExcessProperties.errors.txt`	Adds diagnostic baseline.
`tsc/testdata/baselines/reference/conformance/negatedFreshOptionalProperties(exactoptionalpropertytypes=true).types`	Adds type baseline.
`tsc/testdata/baselines/reference/conformance/negatedFreshOptionalProperties(exactoptionalpropertytypes=true).symbols`	Adds symbol baseline.
`tsc/testdata/baselines/reference/conformance/negatedFreshOptionalProperties(exactoptionalpropertytypes=true).js`	Adds emit baseline.
`tsc/testdata/baselines/reference/conformance/negatedFreshOptionalProperties(exactoptionalpropertytypes=true).errors.txt`	Adds diagnostic baseline.
`tsc/testdata/baselines/reference/conformance/negatedFreshOptionalProperties(exactoptionalpropertytypes=false).types`	Adds type baseline.
`tsc/testdata/baselines/reference/conformance/negatedFreshOptionalProperties(exactoptionalpropertytypes=false).symbols`	Adds symbol baseline.
`tsc/testdata/baselines/reference/conformance/negatedFreshOptionalProperties(exactoptionalpropertytypes=false).js`	Adds emit baseline.
`tsc/testdata/baselines/reference/conformance/negatedFreshOptionalProperties(exactoptionalpropertytypes=false).errors.txt`	Adds diagnostic baseline.
`tsc/testdata/baselines/reference/conformance/logicalOrOperatorWithTypeParameters.errors.txt`	Updates diagnostic baseline.
`tsc/testdata/baselines/reference/conformance/logicalAssignment4(target=esnext).types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/logicalAssignment4(target=es2021).types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/logicalAssignment4(target=es2020).types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/logicalAssignment4(target=es2015).types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/literalTypes3.types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/keyofAndIndexedAccess.types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/intersectionsAndEmptyObjects.types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/controlFlowWithTemplateLiterals.errors.txt`	Updates diagnostic baseline.
`tsc/testdata/baselines/reference/conformance/controlFlowIfStatement.types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/controlFlowGenericTypes.types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/conditionalTypes1.types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/classStaticBlock8.types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/checkJsxChildrenCanBeTupleType.types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/checkJsxChildrenCanBeTupleType.errors.txt`	Updates diagnostic baseline.
`tsc/testdata/baselines/reference/conformance/bivariantInferences.types`	Updates type baseline.
`tsc/testdata/baselines/reference/conformance/assertionTypePredicates1.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/weakTypeAndPrimitiveNarrowing.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/voidUndefinedReduction.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/unusedPrivateStaticMembers.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/unreachableSwitchTypeofUnknown.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/unknownLikeUnionObjectFlagsNotPropagated.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/undefinedAsDiscriminantWithUnknown(strictnullchecks=true).types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/typeVariableConstraintIntersections.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/typePredicateWithThisParameter.errors.txt`	Updates diagnostic baseline.
`tsc/testdata/baselines/reference/compiler/typePredicatesOptionalChaining1.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/typeInferenceTypePredicate.errors.txt`	Updates diagnostic baseline.
`tsc/testdata/baselines/reference/compiler/tsxNotUsingApparentTypeOfSFC.errors.txt`	Updates diagnostic baseline.
`tsc/testdata/baselines/reference/compiler/styledComponentsInstantiaionLimitNotReached.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/strictOptionalProperties1.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/strictNullNotNullIndexTypeNoLib.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/specialIntersectionsInMappedTypes.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/simpleRecursionWithBaseCase1.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/recursiveTypeRelations.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/patternAmbientModuleAugmentationMergedSymbol.errors.txt`	Updates diagnostic baseline.
`tsc/testdata/baselines/reference/compiler/observableInferenceCanBeMade.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/nullishCoalescingAlwaysNullFalsePositive.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/nonNullableTypes1.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/noImplicitAnyForIn.errors.txt`	Updates diagnostic baseline.
`tsc/testdata/baselines/reference/compiler/nestedGenericTypeInference.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/negatedTypeSmokeTypeof(strict=false).errors.txt`	Adds diagnostic baseline.
`tsc/testdata/baselines/reference/compiler/negatedTypeSmokeInference.errors.txt`	Adds diagnostic baseline.
`tsc/testdata/baselines/reference/compiler/negatedPartialTypeGuards.errors.txt`	Adds diagnostic baseline.
`tsc/testdata/baselines/reference/compiler/negatedNumericEnumComparability.types`	Adds type baseline.
`tsc/testdata/baselines/reference/compiler/negatedNumericEnumComparability.errors.txt`	Adds diagnostic baseline.
`tsc/testdata/baselines/reference/compiler/narrowingUnionToUnion.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/narrowingTypeofUndefined2.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/narrowingPastLastAssignment.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/narrowingByTypeofInSwitch.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/narrowByEquality.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/narrowByBooleanComparison.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/mergeSymbolReexportedTypeAliasInstantiation.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/jsxNamespaceImplicitImportJSXNamespace.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/jsxNamespaceGlobalReexportMissingAliasTarget.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/jsxNamespaceGlobalReexport.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/jsxExcessPropsAndAssignability.errors.txt`	Updates diagnostic baseline.
`tsc/testdata/baselines/reference/compiler/inKeywordTypeguard(strict=true).types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/inKeywordTypeguard(strict=true).errors.txt`	Updates diagnostic baseline.
`tsc/testdata/baselines/reference/compiler/inferTypePredicates.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/inferTypePredicates.js`	Updates emit baseline.
`tsc/testdata/baselines/reference/compiler/inferenceExactOptionalProperties2.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/inferenceExactOptionalProperties2.errors.txt`	Updates diagnostic baseline.
`tsc/testdata/baselines/reference/compiler/inferenceDoesNotAddUndefinedOrNull.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/inDoesNotOperateOnPrimitiveTypes.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/inDoesNotOperateOnPrimitiveTypes.errors.txt`	Updates diagnostic baseline.
`tsc/testdata/baselines/reference/compiler/indexerAssignability.errors.txt`	Updates diagnostic baseline.
`tsc/testdata/baselines/reference/compiler/implicitIndexSignatures.errors.txt`	Updates diagnostic baseline.
`tsc/testdata/baselines/reference/compiler/implicitEmptyObjectType.errors.txt`	Removes an existing diagnostic baseline.
`tsc/testdata/baselines/reference/compiler/genericUnboundedTypeParamAssignability.errors.txt`	Updates diagnostic baseline.
`tsc/testdata/baselines/reference/compiler/genericPrototypeProperty3.errors.txt`	Updates diagnostic baseline.
`tsc/testdata/baselines/reference/compiler/genericInferenceDefaultTypeParameterJsxReact.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/fixCrashAliasLookupForDefauledImport.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/expandoContextualTypes.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/excessiveStackDepthFlatArray.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/emptyThenWithoutWarning.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/emptyAnonymousObjectNarrowing(strictnullchecks=true).types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/emptyAnonymousObjectNarrowing(strictnullchecks=false).types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/doubleUnderscoreLabels.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/distributiveConditionalTypeConstraints.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/declFileTypeAnnotationStringLiteral(target=es2015).types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/continueInLoopsWithCapturedBlockScopedBindings1(target=es2015).types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/contextualTypeBasedOnIntersectionWithAnyInTheMix1.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/contextualTypeBasedOnIntersectionWithAnyInTheMix1.errors.txt`	Updates diagnostic baseline.
`tsc/testdata/baselines/reference/compiler/constructorWithCapturedSuper.types`	Updates type baseline.
`tsc/testdata/baselines/reference/compiler/assertionFunctionWildcardImport2.types`	Updates type baseline.
`tsc/internal/scanner/scanner.go`	Recognizes `not` syntax.
`tsc/internal/parser/parser.go`	Parses negated type operators.
`tsc/internal/ls/string_completions.go`	Uses literal origins for completions.
`tsc/internal/ls/hover.go`	Displays literal origins in hover.
`tsc/internal/fourslash/tests/stringLiteralCompletionsForOpenEndedTemplateLiteralType_test.go`	Updates completion expectations.
`tsc/internal/fourslash/tests/specialIntersectionsOrderIndependent_test.go`	Updates intersection completion tests.
`tsc/internal/checker/nodebuilderimpl.go`	Emits negated and non-nullish types.
`tsc/internal/checker/inference.go`	Supports inference through negation.
`tsc/internal/checker/exports.go`	Exposes negated-type construction.
`tsc/internal/api/session.go`	Handles negated-type API requests.
`tsc/internal/api/proto.go`	Registers the API method.
`tsc/internal/api/encoder/encoder_generated.go`	Encodes negated AST nodes.
`tsc/internal/api/encoder/decoder_generated.go`	Decodes negated AST nodes.
`tools/scripts/tsc/ast.json`	Defines negated AST metadata.
`packages/typescript/test/sync/api.test.ts`	Tests synchronous APIs.
`packages/typescript/test/sync/api-generators.test.ts`	Tests generated synchronous APIs.
`packages/typescript/test/async/api.test.ts`	Tests asynchronous APIs.
`packages/typescript/src/enums/typeFlags.enum.ts`	Adds the negated type flag.
`packages/typescript/src/enums/objectFlags.ts`	Updates generated object flags.
`packages/typescript/src/enums/objectFlags.enum.ts`	Adds negation-related object flags.
`packages/typescript/src/ast/factory.generated.ts`	Constructs negated type operators.
`packages/typescript/src/ast/ast.generated.ts`	Adds negated operator AST support.
`packages/typescript/src/api/sync/types.ts`	Exposes synchronous negation APIs.
`packages/typescript/src/api/proto.generated.ts`	Adds generated protocol declarations.
`packages/typescript/src/api/node/node.generated.ts`	Decodes negated operator nodes.
`packages/typescript/src/api/node/encoder.generated.ts`	Encodes negated operator nodes.
`packages/typescript/src/api/async/types.ts`	Exposes asynchronous negation APIs.
`packages/typescript/src/api/async/api.ts`	Implements asynchronous negation calls.

Files not reviewed (1)

tsc/internal/api/enum_values_generated.go: Generated file

+	if c.isNonNullishUnknownType(t) {
+		return c.emptyObjectType


 			Exact: []fourslash.CompletionsExpectedItem{
-				"dataDowncast",
 				"downcast",
-				"editingDowncast",
 			},


        for (const p of arg) {  }
 >p : unknown
->arg : T & {}
+>arg : T & not undefined & not undefined


Wesley Wigham (weswigham) · 2026-09-21T18:06:55Z

TypeScript Bot (@typescript-bot) test top1000

typescript-automation · 2026-09-21T18:07:00Z

Hey Wesley Wigham (@weswigham), this PR changed while I was preparing the test run. Please try again.

Wesley Wigham (weswigham) added 2 commits September 21, 2026 10:40

Copilot AI balanced review requested due to automatic review settings September 21, 2026 17:52

github-project-automation Bot added this to PR Backlog Sep 21, 2026

typescript-automation Bot assigned Wesley Wigham (weswigham) Sep 21, 2026

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Copilot started reviewing on behalf of Wesley Wigham (weswigham) September 21, 2026 17:53 View session

Wesley Wigham (weswigham) closed this Sep 21, 2026

github-project-automation Bot moved this from Not started to Done in PR Backlog Sep 21, 2026

Wesley Wigham (weswigham) reopened this Sep 21, 2026

Wesley Wigham (weswigham) changed the base branch from main to weswigham/negated-types September 21, 2026 18:01

Wesley Wigham (weswigham) added this pull request to stack #64377 September 21, 2026 18:01

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Negated Types: Change the meaning of `{}` to `unknown & not null & not undefined` - #64376

Negated Types: Change the meaning of `{}` to `unknown & not null & not undefined`#64376
Wesley Wigham (weswigham) wants to merge 2 commits into
weswigham/negated-typesfrom
weswigham/negated-types-empty-object-meaning

Wesley Wigham (weswigham) commented Sep 21, 2026 •

edited

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Wesley Wigham (weswigham) commented Sep 21, 2026

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Wesley Wigham (weswigham) commented Sep 21, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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🟡 Changes recommended

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Wesley Wigham (weswigham) commented Sep 21, 2026

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Wesley Wigham (weswigham) commented Sep 21, 2026 •

edited

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