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refactor: Avoid inheritance and ban instanceof #37

Merged
glen merged 2 commits from ban_instanceof into main 2025-12-12 10:21:02 +00:00
Conversation 0 Commits 2 Files changed 6 +74 -38
6 changed files with 74 additions and 38 deletions
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2
src/boolean/__test__/type.spec.js
View file

@ -19,7 +19,7 @@ describe('boolean type functions', () => {
})
it('converts any type to boolean', () => {
for (const T in math.types) {
if (T instanceof Type) assert(boolean.resolve([T]))
if (Type.holds(T)) assert(boolean.resolve([T]))
}
})
})

12
src/core/Implementations.js
View file

@ -1,13 +1,23 @@
const implementationsBrand = Symbol()
export class Implementations {
constructor(impOrImps) {
if (Array.isArray(impOrImps)) {
this.matchers = impOrImps
} else this.matchers = [impOrImps]
}
this[implementationsBrand] = true
}
// Returns true if entity is an Implementations
static holds(entity) {return entity[implementationsBrand]}
}
const igBrand = Symbol()
export class ImplementationsGenerator {
constructor(f) {
this.generate = f
this[igBrand] = true
}
// Returns true if entity is an ImplementationsGenerator
static holds(entity) {return entity[igBrand]}
}

16
src/core/Type.js
View file

@ -1,5 +1,7 @@
import ArrayKeyedMap from 'array-keyed-map'
const typeBrand = Symbol() // invisible outside this file
// Generic types are callable, so we have no choice but to extend Function
export class Type extends Function {
constructor(f, options = {}) {
@ -19,6 +21,7 @@ export class Type extends Function {
}
})
this[typeBrand] = true
this.test = f
// we want property `from` to end up as an array of Matchers:
this.from = options.from
@ -57,15 +60,16 @@ export class Type extends Function {
return rewired
}
toString() {
return this.typeName || `[Type ${this.test}]`
}
toString() {return this.typeName || `[Type ${this.test}]`}
// Returns true if entity is a Type
static holds(entity) {return entity[typeBrand]}
}
export const Undefined = new Type(
t => typeof t === 'undefined',
{zero: undefined, one: undefined, nan: undefined})
export const TypeOfTypes = new Type(t => t instanceof Type)
export const TypeOfTypes = new Type(t => Type.holds(t))
export const Unknown = new Type(() => true) // Danger, do not merge!
Unknown._doNotMerge = true
@ -74,7 +78,7 @@ export const OneOf = (...types) => {
if (!types.length) {
throw new RangeError('cannot choose OneOf no types at all')
}
const nonType = types.findIndex(T => !(T instanceof Type))
const nonType = types.findIndex(T => !Type.holds(T))
if (nonType >= 0) {
throw new RangeError(
`OneOf can only take type arguments, not ${types[nonType]}`)
@ -106,7 +110,7 @@ export const ReturnType = f => f.returns ?? Unknown
export const whichType = typs => Returns(TypeOfTypes, item => {
for (const type of Object.values(typs)) {
if (!(type instanceof Type)) continue
if (!Type.holds(type)) continue
if (type.test(item)) return type.refine(item, whichType(typs))
}
let errorMsg = ''

19
src/core/TypeDispatcher.js
View file

@ -81,10 +81,10 @@ export class TypeDispatcher {
// For special cases like types, config, etc, we can wrap
// a function in ImplementationsGenerator to produce the thing
// we should really merge:
if (val instanceof ImplementationsGenerator) val = val.generate()
if (ImplementationsGenerator.holds(val)) val = val.generate()
// Now dispatch on what sort of thing we are supposed to merge:
if (val instanceof Type) {
if (Type.holds(val)) {
if (val._doNotMerge) {
throw new TypeError(`attempt to merge unusable type '${val}'`)
}
@ -105,13 +105,13 @@ export class TypeDispatcher {
// Everything else we coerce into Implementations and deal with
// right here:
if (val instanceof Matcher) val = new Implementations(val)
if (Matcher.holds(val)) val = new Implementations(val)
if (Array.isArray(val)) val = new Implementations(val)
if (isPlainFunction(val)) {
throw new RangeError(
`function value for ${key} must be merged within a 'match' call`)
}
if (!(val instanceof Implementations)) {
if (!Implementations.holds(val)) {
val = new Implementations(match(Passthru, val))
}
@ -307,7 +307,7 @@ export class TypeDispatcher {
}
if (generatingDeps
&& typeof result === 'object'
&& !(result instanceof Type)
&& !Type.holds(result)
) {
return DependencyRecorder(result, key, this, bhvix)
}
@ -354,7 +354,7 @@ export class TypeDispatcher {
behave.set(bhvix, item)
if (generatingDeps
&& typeof item === 'object'
&& !(item instanceof Type)
&& !Type.holds(item)
) {
return DependencyRecorder(item, key, this, bhvix)
}
@ -469,7 +469,8 @@ const DependencyRecorder = (object, path, repo, bhvix) => new Proxy(object, {
const result = Reflect.get(target, prop, receiver)
// pass internal methods through, as well as resolve calls,
// since we record dependencies within the latter:
if (prop.startsWith('_')
if (typeof prop === 'symbol'
|| prop.startsWith('_')
|| prop === 'resolve'
|| (typeof result === 'function' && 'isDispatcher' in result)
) {
@ -484,7 +485,7 @@ const DependencyRecorder = (object, path, repo, bhvix) => new Proxy(object, {
// dependencies on its properties (e.g. math.config.predictable)
// So proxy the return value, except for types, which must maintain
// strict referential identity:
if (typeof result === 'object' && !(result instanceof Type)) {
if (typeof result === 'object' && !Type.holds(result)) {
return DependencyRecorder(result, newPath, repo, bhvix)
} else return result
}
@ -508,7 +509,7 @@ const DependencyWatcher = (object, path, ixList, repo) => new Proxy(object, {
get(target, prop, receiver) {
// Only thing we need to do is push the watching down
const result = Reflect.get(target, prop, receiver)
if (typeof result === 'object' && !(result instanceof Type)) {
if (typeof result === 'object' && !Type.holds(result)) {
const newPath = [path, prop].join('.')
return DependencyWatcher(result, newPath, ixList, repo)
}

61
src/core/TypePatterns.js
View file

@ -1,20 +1,27 @@
import {ReturnType, Type, Undefined, Unknown} from './Type.js'
import {isPlainFunction} from './helpers.js'
const tpBrand = Symbol()
export class TypePattern {
constructor() {
throw new Error('Cannot construct an abstract TypePattern')
}
match(_typeSequence, _options={}) {
throw new Error('Specific TypePatterns must implement match')
}
sampleTypes() {
throw new Error('Specific TypePatterns must implement sampleTypes')
}
equal(other) {return other.constructor === this.constructor}
toString() {return 'Abstract Pattern (?!)'}
// Returns true if entity is a TypePattern
static holds(entity) {return entity[tpBrand]}
}
class MatchTypePattern extends TypePattern {
class MatchTypePattern {
constructor(typeToMatch) {
super()
this[tpBrand] = true
this.type = typeToMatch
}
match(typeSequence, options={}) {
@ -34,13 +41,15 @@ class MatchTypePattern extends TypePattern {
return [-1, Undefined]
}
sampleTypes() {return [this.type]}
equal(other) {return super.equal(other) && this.type === other.type}
equal(other) {
return this.constructor === other.constructor && this.type === other.type
}
toString() {return `Match(${this.type})`}
}
class SequencePattern extends TypePattern {
class SequencePattern {
constructor(itemsToMatch) {
super()
this[tpBrand] = true
this.patterns = itemsToMatch.map(pattern)
}
match(typeSequence, options={_internal: true}) {
@ -62,16 +71,16 @@ class SequencePattern extends TypePattern {
return this.patterns.map(pat => pat.sampleTypes()).flat()
}
equal(other) {
return super.equal(other)
return this.constructor === other.constructor
&& this.patterns.length === other.patterns.length
&& this.patterns.every((elt, ix) => elt.equal(other.patterns[ix]))
}
toString() {return `[${this.patterns}]`}
}
class PredicatePattern extends TypePattern {
class PredicatePattern {
constructor(predicate) {
super()
this[tpBrand] = true
this.predicate = predicate
}
match(typeSequence, options={}) {
@ -85,14 +94,15 @@ class PredicatePattern extends TypePattern {
throw new Error('sampleTypes() not yet implemented for PredicatePattern')
}
equal(other) {
return super.equal(other) && this.predicate === other.predicate
return this.constructor === other.constructor
&& this.predicate === other.predicate
}
toString() {return `Test(${this.predicate})`}
}
export const pattern = patternOrSpec => {
if (patternOrSpec instanceof TypePattern) return patternOrSpec
if (patternOrSpec instanceof Type) {
if (TypePattern.holds(patternOrSpec)) return patternOrSpec
if (Type.holds(patternOrSpec)) {
return new MatchTypePattern(patternOrSpec)
}
if (Array.isArray(patternOrSpec)) return new SequencePattern(patternOrSpec)
@ -102,7 +112,8 @@ export const pattern = patternOrSpec => {
throw new TypeError(`Can't interpret '${patternOrSpec}' as a type pattern`)
}
class AnyPattern extends TypePattern {
class AnyPattern {
constructor () {this[tpBrand] = true}
match(typeSequence, options={}) {
const position = options.position ?? 0
return position < typeSequence.length
@ -110,14 +121,15 @@ class AnyPattern extends TypePattern {
: [-1, Undefined]
}
sampleTypes() {return [Undefined]}
equal(other) {return this.constructor === other.constructor}
toString() {return 'Any'}
}
export const Any = new AnyPattern()
class OptionalPattern extends TypePattern {
class OptionalPattern {
constructor(item) {
super()
this[tpBrand] = true
this.pattern = pattern(item)
}
match(typeSequence, options={_internal: true}) {
@ -135,16 +147,17 @@ class OptionalPattern extends TypePattern {
}
sampleTypes() {return []}
equal(other) {
return super.equal(other) && this.pattern.equal(other.pattern)
return this.constructor === other.constructor
&& this.pattern.equal(other.pattern)
}
toString() {return `?${this.pattern}`}
}
export const Optional = item => new OptionalPattern(item)
class MultiPattern extends TypePattern {
class MultiPattern {
constructor(item) {
super()
this[tpBrand] = true
this.pattern = pattern(item)
}
match(typeSequence, options={_internal: true}) {
@ -162,7 +175,8 @@ class MultiPattern extends TypePattern {
}
sampleTypes() {return []}
equal(other) {
return super.equal(other) && this.pattern.equal(other.pattern)
return this.constructor === other.constructor
&& this.pattern.equal(other.pattern)
}
toString() {return `${this.pattern}*`}
}
@ -171,13 +185,15 @@ export const Multiple = item => new MultiPattern(item)
// Like Multiple(Any) except leaves the argument list alone; it doesn't
// chunk it into a single Array of all arguments
class PassthruPattern extends TypePattern {
class PassthruPattern {
constructor () {this[tpBrand] = true}
match(typeSequence, options={}) {
const position = options.position ?? 0
return [typeSequence.length, typeSequence.slice(position)]
}
sampleTypes() {return []}
toString() {return 'Passthru'}
equal(other) {return this.constructor === other.constructor}
}
export const Passthru = new PassthruPattern()
@ -206,11 +222,16 @@ export const needsCollection = (template) => {
return 'actual' in template
}
const matcherBrand = Symbol()
export class Matcher {
constructor(spec, facOrBehave) {
this.pattern = pattern(spec)
this.does = facOrBehave
this[matcherBrand] = true
}
// Returns true if entity is a matcher
static holds(entity) {return entity[matcherBrand]}
}
export const match = (spec, facOrBehave) => new Matcher(spec, facOrBehave)

4
src/core/__test__/helpers.spec.js
View file

@ -7,8 +7,8 @@ import {match, Matcher, TypePattern} from '../TypePatterns.js'
describe('Core helpers', () => {
it('defines what Matchers are', () => {
const matcher = match([TypeOfTypes, Undefined], -3)
assert(matcher instanceof Matcher)
assert(matcher.pattern instanceof TypePattern)
assert(Matcher.holds(matcher))
assert(TypePattern.holds(matcher.pattern))
})
it('detects plain objects', () => {