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Consider identical instances of the same symbol equivalent when creating union and intersection properties (#43560)

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* Consider identical instances of the same symbol equivalent when creating union and intersection properties

* Also copy over mapper and type (if available) on cloned symbols

* Editorial feedback
This commit is contained in:
Wesley Wigham
2021-04-14 16:55:45 -07:00
committed by GitHub
parent 6c7c5e9ec2
commit 3ab6809e38
19 changed files with 170 additions and 37 deletions
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39
src/compiler/checker.ts
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@@ -11641,6 +11641,7 @@ namespace ts {
let optionalFlag = isUnion ? SymbolFlags.None : SymbolFlags.Optional;
let syntheticFlag = CheckFlags.SyntheticMethod;
let checkFlags = 0;
let mergedInstantiations = false;
for (const current of containingType.types) {
const type = getApparentType(current);
if (!(type === errorType || type.flags & TypeFlags.Never)) {
@@ -11657,13 +11658,25 @@ namespace ts {
singleProp = prop;
}
else if (prop !== singleProp) {
if (!propSet) {
propSet = new Map<SymbolId, Symbol>();
propSet.set(getSymbolId(singleProp), singleProp);
const isInstantiation = (getTargetSymbol(prop) || prop) === (getTargetSymbol(singleProp) || singleProp);
// If the symbols are instances of one another with identical types - consider the symbols
// equivalent and just use the first one, which thus allows us to avoid eliding private
// members when intersecting a (this-)instantiations of a class with it's raw base or another instance
if (isInstantiation && isPropertyIdenticalTo(singleProp, prop)) {
// If we merged instantiations of a generic type, we replicate the symbol parent resetting behavior we used
// to do when we recorded multiple distinct symbols so that we still get, eg, `Array<T>.length` printed
// back and not `Array<string>.length` when we're looking at a `.length` access on a `string[] | number[]`
mergedInstantiations = !!singleProp.parent && !!length(getLocalTypeParametersOfClassOrInterfaceOrTypeAlias(singleProp.parent));
}
const id = getSymbolId(prop);
if (!propSet.has(id)) {
propSet.set(id, prop);
else {
if (!propSet) {
propSet = new Map<SymbolId, Symbol>();
propSet.set(getSymbolId(singleProp), singleProp);
}
const id = getSymbolId(prop);
if (!propSet.has(id)) {
propSet.set(id, prop);
}
}
}
checkFlags |= (isReadonlySymbol(prop) ? CheckFlags.Readonly : 0) |
@@ -11697,7 +11710,19 @@ namespace ts {
return undefined;
}
if (!propSet && !(checkFlags & CheckFlags.ReadPartial) && !indexTypes) {
return singleProp;
if (mergedInstantiations) {
// No symbol from a union/intersection should have a `.parent` set (since unions/intersections don't act as symbol parents)
// Unless that parent is "reconstituted" from the "first value declaration" on the symbol (which is likely different than its instantiated parent!)
// They also have a `.containingType` set, which affects some services endpoints behavior, like `getRootSymbol`
const clone = createSymbolWithType(singleProp, (singleProp as TransientSymbol).type);
clone.parent = singleProp.valueDeclaration?.symbol?.parent;
clone.containingType = containingType;
clone.mapper = (singleProp as TransientSymbol).mapper;
return clone;
}
else {
return singleProp;
}
}
const props = propSet ? arrayFrom(propSet.values()) : [singleProp];
let declarations: Declaration[] | undefined;