* Switch index signature storage to 'indexInfos: IndexInfo[]' property
* Accept new baselines
* Remove another usage of IndexKind enum
* Update getIndexedAccessType and resolveMappedTypeMembers
* Accept new baselines
* Update grammar checking for index signatures
* Accept new baselines
* Consider all index signatures in mapped types and union types
* Accept new baselines
* Update getIndexType
* Accept new baselines
* Intersect multiple applicable index signatures
* Use getApplicableIndexInfo instead of hardwired string/number handling
* Update index signature relationship checking
* Report type for which index signature is missing
* Report type for which index signature is missing
* Accept new baselines
* Make 'number' index signatures consistently apply to numeric strings
* Accept new baselines
* Update fourslash test
* Revise index constraint checking
* Accept new baselines
* Update error messages
* Accept new baselines
* Update type inference from index signatures
* Update isKnownProperty
* Update contextual typing based on index signatures
* Accept new baselines
* Support union types in index signature declarations
* Accept new baselines
* Check duplicate index signatures / remove redundant template literals from unions with string
* Accept new baselines
* Include key type in diagnostic / check symbol-named properties
* Accept new baselines
* Minor fix
* Add tests
* Accept new baselines
* Add optimized findApplicableIndexInfoForName
* Accept new baselines
* Another place we don't need to obtain literal type for property name
* Accept new baselines
* Don't create literal types that are going to be discarded
* Individual maps for string, number, bigint, and enum literal types
* Remove ineffective optimizations
* Accept new baselines
* Permit intersections as key types in index signatures
* Index expression in element access is template literal context
* Add tests
* Accept new baselines
* Symbol index signatures from object literals with computed symbol properties
* Accept new baselines
* Add more tests
* Accept new baselines
* Implement Go To Definition for all applicable index signatures
* Add fourslash test
* Accept new API baselines
* Enable '--strictNullChecks'
* Fix API baselines
* Make sys.getEnvironmentVariable non-nullable
* make properties optional instead of using `| undefined` in thier type
* reportDiagnostics should be required
* Declare firstAccessor as non-nullable
* Make `some` a type guard
* Fix `getEnvironmentVariable` definition in tests
* Pretend transformFlags are always defined
* Fix one more use of sys.getEnvironmentVariable
* `requiredResponse` accepts undefined, remove assertions
* Mark optional properties as optional instead of using `| undefined`
* Mark optional properties as optional instead of using ` | undefined`
* Remove unnecessary null assertions
* Put the bang on the declaration instead of every use
* Make `createMapFromTemplate` require a parameter
* Mark `EmitResult.emittedFiles` and `EmitResult.sourceMaps` as optional
* Plumb through undefined in emitLsit and EmitExpressionList
* `ElementAccessExpression.argumentExpression` can not be `undefined`
* Add overloads for `writeTokenText`
* Make `shouldWriteSeparatingLineTerminator` argument non-nullable
* Make `synthesizedNodeStartsOnNewLine` argument required
* `PropertyAssignment.initializer` cannot be undefined
* Use one `!` at declaration site instead of on every use site
* Capture host in a constant and avoid null assertions
* Remove few more unused assertions
* Update baselines
* Use parameter defaults
* Update baselines
* Fix lint
* Make Symbol#valueDeclaration and Symbol#declarations non-optional to reduce assertions
* Make Node#symbol and Type#symbol non-optional to reduce assertions
* Make `flags` non-nullable to reduce assertions
* Convert some asserts to type guards
* Make `isNonLocalAlias` a type guard
* Add overload for `getSymbolOfNode` for `Declaration`
* Some more `getSymbolOfNode` changes
* Push undefined suppression into `typeToTypeNodeHelper`
* `NodeBuilderContext.tracker` is never `undefined`
* use `Debug.assertDefined`
* Remove unnecessary tag
* Mark `LiteralType.freshType` and `LiteralTupe.regularType` as required
* Lazily compute signature type predicates
* Use an instance of IdentifierTypePredicate to represent an unresolved type predicate
* Simplify `getMaybeTypePredicate`
* Invert representation of `resolvedTypePredicate`
* Remove `__unresolvedTypePredicate` type and remember to use `noTypePredicate` instead of `undefined` when in all `createSignature` calls
* Fix style of getTypePredicateOfSignature
* Use in createGetSymbolWalker
* Fix bugs for unions of type predicates
* Code review
* Make noTypePredicate purely an implementation detail of getTypePredictateOfSignature
* Add test
* Add test for #19642
* Add test with reversed order
