diff --git a/src/Chunk.ts b/src/Chunk.ts
index a9b0f195ea9..bcf96ebb293 100644
--- a/src/Chunk.ts
+++ b/src/Chunk.ts
@@ -725,9 +725,7 @@ export default class Chunk {
 		const map = module.getExportNamesByVariable();
 		for (const exportedVariable of map.keys()) {
 			const isSynthetic = exportedVariable instanceof SyntheticNamedExportVariable;
-			const importedVariable = isSynthetic
-				? (exportedVariable as SyntheticNamedExportVariable).getBaseVariable()
-				: exportedVariable;
+			const importedVariable = isSynthetic ? exportedVariable.getBaseVariable() : exportedVariable;
 			if (!(importedVariable instanceof NamespaceVariable && this.outputOptions.preserveModules)) {
 				this.checkCircularDependencyImport(importedVariable, module);
 				const exportingModule = importedVariable.module;
diff --git a/src/Graph.ts b/src/Graph.ts
index 8feb0765a5c..db02abed7cd 100644
--- a/src/Graph.ts
+++ b/src/Graph.ts
@@ -91,7 +91,7 @@ export default class Graph {
 			watcher.onCurrentRun('close', handleClose);
 		}
 		this.pluginDriver = new PluginDriver(this, options, options.plugins, this.pluginCache);
-		this.acornParser = acorn.Parser.extend(...(options.acornInjectPlugins as any));
+		this.acornParser = acorn.Parser.extend(...(options.acornInjectPlugins as any[]));
 		this.moduleLoader = new ModuleLoader(this, this.modulesById, this.options, this.pluginDriver);
 		this.fileOperationQueue = new Queue(options.maxParallelFileOps);
 	}
diff --git a/src/ModuleLoader.ts b/src/ModuleLoader.ts
index 78cd2a443e3..1c6f36db70d 100644
--- a/src/ModuleLoader.ts
+++ b/src/ModuleLoader.ts
@@ -58,9 +58,9 @@ type NormalizedResolveIdWithoutDefaults = Partial<PartialNull<ModuleOptions>> &
 	id: string;
 };
 
-type ResolveStaticDependencyPromise = Promise<[source: string, resolvedId: ResolvedId]>;
+type ResolveStaticDependencyPromise = Promise<readonly [source: string, resolvedId: ResolvedId]>;
 type ResolveDynamicDependencyPromise = Promise<
-	[dynamicImport: DynamicImport, resolvedId: ResolvedId | string | null]
+	readonly [dynamicImport: DynamicImport, resolvedId: ResolvedId | string | null]
 >;
 type LoadModulePromise = Promise<
 	[
@@ -548,7 +548,7 @@ export class ModuleLoader {
 			if (resolvedId && typeof resolvedId === 'object') {
 				dynamicImport.id = resolvedId.id;
 			}
-			return [dynamicImport, resolvedId] as [DynamicImport, ResolvedId | string | null];
+			return [dynamicImport, resolvedId] as const;
 		});
 	}
 
@@ -567,7 +567,7 @@ export class ModuleLoader {
 							module.id,
 							assertions
 						))
-				] as [string, ResolvedId]
+				] as const
 		);
 	}
 
diff --git a/src/rollup/types.d.ts b/src/rollup/types.d.ts
index 0ebdc347db9..70805021277 100644
--- a/src/rollup/types.d.ts
+++ b/src/rollup/types.d.ts
@@ -1,9 +1,14 @@
 export const VERSION: string;
 
-type FalsyValue = false | null | undefined;
+// utils
+type NullValue = null | undefined | void;
 type MaybeArray<T> = T | T[];
 type MaybePromise<T> = T | Promise<T>;
 
+type PartialNull<T> = {
+	[P in keyof T]: T[P] | null;
+};
+
 export interface RollupError extends RollupLog {
 	name?: string;
 	stack?: string;
@@ -82,10 +87,6 @@ export interface SourceMap {
 
 export type SourceMapInput = ExistingRawSourceMap | string | null | { mappings: '' };
 
-type PartialNull<T> = {
-	[P in keyof T]: T[P] | null;
-};
-
 interface ModuleOptions {
 	assertions: Record<string, string>;
 	meta: CustomPluginOptions;
@@ -224,7 +225,7 @@ interface PartialResolvedId extends Partial<PartialNull<ModuleOptions>> {
 	id: string;
 }
 
-export type ResolveIdResult = string | false | null | void | PartialResolvedId;
+export type ResolveIdResult = string | NullValue | false | PartialResolvedId;
 
 export type ResolveIdHook = (
 	this: PluginContext,
@@ -252,11 +253,11 @@ export type IsExternal = (
 	isResolved: boolean
 ) => boolean;
 
-export type IsPureModule = (id: string) => boolean | null | void;
+export type IsPureModule = (id: string) => boolean | NullValue;
 
 export type HasModuleSideEffects = (id: string, external: boolean) => boolean;
 
-export type LoadResult = SourceDescription | string | null | void;
+export type LoadResult = SourceDescription | string | NullValue;
 
 export type LoadHook = (this: PluginContext, id: string) => LoadResult;
 
@@ -264,7 +265,7 @@ export interface TransformPluginContext extends PluginContext {
 	getCombinedSourcemap: () => SourceMap;
 }
 
-export type TransformResult = string | null | void | Partial<SourceDescription>;
+export type TransformResult = string | NullValue | Partial<SourceDescription>;
 
 export type TransformHook = (
 	this: TransformPluginContext,
@@ -280,7 +281,7 @@ export type RenderChunkHook = (
 	chunk: RenderedChunk,
 	options: NormalizedOutputOptions,
 	meta: { chunks: Record<string, RenderedChunk> }
-) => { code: string; map?: SourceMapInput } | string | null | undefined;
+) => { code: string; map?: SourceMapInput } | string | NullValue;
 
 export type ResolveDynamicImportHook = (
 	this: PluginContext,
@@ -293,7 +294,7 @@ export type ResolveImportMetaHook = (
 	this: PluginContext,
 	property: string | null,
 	options: { chunkId: string; format: InternalModuleFormat; moduleId: string }
-) => string | null | void;
+) => string | NullValue;
 
 export type ResolveFileUrlHook = (
 	this: PluginContext,
@@ -305,7 +306,7 @@ export type ResolveFileUrlHook = (
 		referenceId: string;
 		relativePath: string;
 	}
-) => string | null | void;
+) => string | NullValue;
 
 export type AddonHookFunction = (
 	this: PluginContext,
@@ -351,8 +352,8 @@ export interface FunctionPluginHooks {
 	) => void;
 	load: LoadHook;
 	moduleParsed: ModuleParsedHook;
-	options: (this: MinimalPluginContext, options: InputOptions) => InputOptions | null | void;
-	outputOptions: (this: PluginContext, options: OutputOptions) => OutputOptions | null | void;
+	options: (this: MinimalPluginContext, options: InputOptions) => InputOptions | NullValue;
+	outputOptions: (this: PluginContext, options: OutputOptions) => OutputOptions | NullValue;
 	renderChunk: RenderChunkHook;
 	renderDynamicImport: (
 		this: PluginContext,
@@ -362,7 +363,7 @@ export interface FunctionPluginHooks {
 			moduleId: string;
 			targetModuleId: string | null;
 		}
-	) => { left: string; right: string } | null | void;
+	) => { left: string; right: string } | NullValue;
 	renderError: (this: PluginContext, error?: Error) => void;
 	renderStart: (
 		this: PluginContext,
@@ -481,13 +482,13 @@ interface ManualChunkMeta {
 	getModuleIds: () => IterableIterator<string>;
 	getModuleInfo: GetModuleInfo;
 }
-export type GetManualChunk = (id: string, meta: ManualChunkMeta) => string | null | void;
+export type GetManualChunk = (id: string, meta: ManualChunkMeta) => string | NullValue;
 
 export type ExternalOption =
 	| (string | RegExp)[]
 	| string
 	| RegExp
-	| ((source: string, importer: string | undefined, isResolved: boolean) => boolean | null | void);
+	| ((source: string, importer: string | undefined, isResolved: boolean) => boolean | NullValue);
 export type PureModulesOption = boolean | string[] | IsPureModule;
 export type GlobalsOption = { [name: string]: string } | ((name: string) => string);
 export type InputOption = string | string[] | { [entryAlias: string]: string };
@@ -499,7 +500,7 @@ export type SourcemapPathTransformOption = (
 	sourcemapPath: string
 ) => string;
 
-export type InputPluginOption = MaybePromise<Plugin | FalsyValue | InputPluginOption[]>;
+export type InputPluginOption = MaybePromise<Plugin | NullValue | false | InputPluginOption[]>;
 
 export interface InputOptions {
 	acorn?: Record<string, unknown>;
@@ -517,7 +518,7 @@ export interface InputOptions {
 	maxParallelFileOps?: number;
 	/** @deprecated Use the "maxParallelFileOps" option instead. */
 	maxParallelFileReads?: number;
-	moduleContext?: ((id: string) => string | null | void) | { [id: string]: string };
+	moduleContext?: ((id: string) => string | NullValue) | { [id: string]: string };
 	onwarn?: WarningHandlerWithDefault;
 	perf?: boolean;
 	plugins?: InputPluginOption;
@@ -623,7 +624,7 @@ export type NormalizedAmdOptions = (
 
 type AddonFunction = (chunk: RenderedChunk) => string | Promise<string>;
 
-type OutputPluginOption = MaybePromise<OutputPlugin | FalsyValue | OutputPluginOption[]>;
+type OutputPluginOption = MaybePromise<OutputPlugin | NullValue | false | OutputPluginOption[]>;
 
 export interface OutputOptions {
 	amd?: AmdOptions;
diff --git a/src/utils/options/mergeOptions.ts b/src/utils/options/mergeOptions.ts
index 5071374422d..be429cfb598 100644
--- a/src/utils/options/mergeOptions.ts
+++ b/src/utils/options/mergeOptions.ts
@@ -5,8 +5,7 @@ import type {
 	OutputOptions,
 	RollupCache,
 	RollupOptions,
-	WarningHandler,
-	WarningHandlerWithDefault
+	WarningHandler
 } from '../../rollup/types';
 import { ensureArray } from '../ensureArray';
 import type { CommandConfigObject } from './normalizeInputOptions';
@@ -159,7 +158,7 @@ async function mergeInputOptions(
 }
 
 const getExternal = (config: InputOptions, overrides: CommandConfigObject): ExternalOption => {
-	const configExternal = config.external as ExternalOption | undefined;
+	const configExternal = config.external;
 	return typeof configExternal === 'function'
 		? (source: string, importer: string | undefined, isResolved: boolean) =>
 				configExternal(source, importer, isResolved) || overrides.external.includes(source)
@@ -167,9 +166,7 @@ const getExternal = (config: InputOptions, overrides: CommandConfigObject): Exte
 };
 
 const getOnWarn = (config: InputOptions, defaultOnWarnHandler: WarningHandler): WarningHandler =>
-	config.onwarn
-		? warning => (config.onwarn as WarningHandlerWithDefault)(warning, defaultOnWarnHandler)
-		: defaultOnWarnHandler;
+	config.onwarn ? warning => config.onwarn!(warning, defaultOnWarnHandler) : defaultOnWarnHandler;
 
 const getObjectOption = <T extends object>(
 	config: T,
diff --git a/src/utils/options/normalizeInputOptions.ts b/src/utils/options/normalizeInputOptions.ts
index d28675db19d..52b941b3812 100644
--- a/src/utils/options/normalizeInputOptions.ts
+++ b/src/utils/options/normalizeInputOptions.ts
@@ -186,7 +186,7 @@ const getmaxParallelFileOps = (
 	warn: WarningHandler,
 	strictDeprecations: boolean
 ): NormalizedInputOptions['maxParallelFileOps'] => {
-	const maxParallelFileReads = config.maxParallelFileReads as unknown;
+	const maxParallelFileReads = config.maxParallelFileReads;
 	if (typeof maxParallelFileReads === 'number') {
 		warnDeprecationWithOptions(
 			'The "maxParallelFileReads" option is deprecated. Use the "maxParallelFileOps" option instead.',
@@ -195,7 +195,7 @@ const getmaxParallelFileOps = (
 			strictDeprecations
 		);
 	}
-	const maxParallelFileOps = (config.maxParallelFileOps as unknown) ?? maxParallelFileReads;
+	const maxParallelFileOps = config.maxParallelFileOps ?? maxParallelFileReads;
 	if (typeof maxParallelFileOps === 'number') {
 		if (maxParallelFileOps <= 0) return Infinity;
 		return maxParallelFileOps;
diff --git a/src/utils/options/normalizeOutputOptions.ts b/src/utils/options/normalizeOutputOptions.ts
index 3e0797e9908..e03e92eba9b 100644
--- a/src/utils/options/normalizeOutputOptions.ts
+++ b/src/utils/options/normalizeOutputOptions.ts
@@ -287,7 +287,7 @@ const getAddon = <T extends 'banner' | 'footer' | 'intro' | 'outro'>(
 	if (typeof configAddon === 'function') {
 		return configAddon as NormalizedOutputOptions[T];
 	}
-	return () => (configAddon as string) || '';
+	return () => configAddon || '';
 };
 
 // eslint-disable-next-line unicorn/prevent-abbreviations
diff --git a/src/utils/renderChunks.ts b/src/utils/renderChunks.ts
index dae3bc5f38b..74bbf60c16e 100644
--- a/src/utils/renderChunks.ts
+++ b/src/utils/renderChunks.ts
@@ -161,10 +161,7 @@ async function transformChunk(
 		map.sources = map.sources
 			.map(sourcePath => {
 				if (sourcemapPathTransform) {
-					const newSourcePath = sourcemapPathTransform(
-						sourcePath,
-						`${resultingFile}.map`
-					) as unknown;
+					const newSourcePath = sourcemapPathTransform(sourcePath, `${resultingFile}.map`);
 
 					if (typeof newSourcePath !== 'string') {
 						error(errorFailedValidation(`sourcemapPathTransform function must return a string.`));