Remove unnecessary type assertions

[ulrichstark]

While testing my changes to the @typescript-eslint/no-unnecessary-type-assertion lint rule on this repo, I found these unnecessary type assertions that can be removed without impacting runtime behaviour or triggering TS errors.

typescript-eslint/typescript-eslint#11789

[typescript-bot]

This PR doesn't have any linked issues. Please open an issue that references this PR. From there we can discuss and prioritise.

[typescript-bot]

This PR doesn't have any linked issues. Please open an issue that references this PR. From there we can discuss and prioritise.

[Copilot]

Pull request overview

This pull request removes unnecessary type assertions across the TypeScript codebase that were identified by improvements to the @typescript-eslint/no-unnecessary-type-assertion lint rule. The changes are purely cosmetic, removing as Type assertions where TypeScript's type inference already provides the correct type information.

Key changes:

• Removal of redundant type assertions in type guard contexts (e.g., after flags & TypeFlags.TypeParameter checks)
• Elimination of unnecessary casts where function signatures already accept the broader type
• Cleanup of assertions where factory methods return the correct specific type

Reviewed changes

Copilot reviewed 25 out of 25 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/testRunner/unittests/tsserver/inlayHints.ts	Removed unnecessary assertion on preferences object
src/testRunner/projectsRunner.ts	Removed redundant string assertion on baseline content
src/services/symbolDisplay.ts	Removed type assertion where type parameter check provides correct type
src/services/stringCompletions.ts	Removed host interface assertions where type is already compatible
src/services/services.ts	Removed SyntaxKind assertion on Number() result
src/services/getEditsForFileRename.ts	Removed ModuleResolutionHost assertion
src/services/findAllReferences.ts	Removed assertion on findAncestor result with type guard
src/services/completions.ts	Removed ObjectTypeDeclaration assertion on findAncestor
src/services/codefixes/generateAccessors.ts	Removed assertion on declaration.name.text
src/services/codefixes/fixUnreferenceableDecoratorMetadata.ts	Removed assertion on or() predicate result
src/services/classifier.ts	Removed ClassificationType assertion on array access
src/server/utilitiesPublic.ts	Removed NormalizedPath[] assertion on concat
src/server/session.ts	Removed string assertion on symlinkedPath
src/server/project.ts	Removed SortedReadonlyArray assertion on emptyArray
src/server/editorServices.ts	Removed ProgramUpdateLevel assertion on Math.max result
src/compiler/utilitiesPublic.ts	Removed Identifier assertion where type is already known
src/compiler/utilities.ts	Removed NonNullable assertion on generic parameter
src/compiler/tsbuildPublic.ts	Removed CompilerHost & ReadBuildProgramHost assertion
src/compiler/transformers/ts.ts	Removed ModuleDeclaration assertion after type check
src/compiler/transformers/es2018.ts	Removed NodeCheckFlags assertion on literal 0
src/compiler/symbolWalker.ts	Removed TypeParameter assertion after flags check
src/compiler/parser.ts	Removed callback type assertions for forEachChild
src/compiler/emitter.ts	Removed DotToken, Modifier[], and Decorator[] assertions
src/compiler/checker.ts	Removed 50+ TypeParameter, UnionType, and other type assertions after flag checks
src/compiler/binder.ts	Removed Identifier assertions where function accepts broader Node type

[jakebailey]

Those are good improvements but I would doubt we'd merge this given the current TS codebase is going to get overwritten in the somewhat near future: #62963

[ulrichstark]

Those are good improvements but I would doubt we'd merge this given the current TS codebase is going to get overwritten in the somewhat near future: #62963

Thanks and no worries! You can close the PR if you want. This was more of a proof of concept for my lint changes, but I wanted to propose them anyway.