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Discriminate contextual types (#19733)

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* Discriminate contextual types

* Invert conditional

* Update findMatchingDiscriminantType and baselines
This commit is contained in:
Wesley Wigham
2017-11-06 16:09:35 -08:00
committed by GitHub
parent d6436f13e5
commit d79c37cd19
10 changed files with 262 additions and 26 deletions
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59
src/compiler/checker.ts
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@@ -9269,20 +9269,24 @@ namespace ts {
return Ternary.False;
}
// Keep this up-to-date with the same logic within `getApparentTypeOfContextualType`, since they should behave similarly
function findMatchingDiscriminantType(source: Type, target: UnionOrIntersectionType) {
let match: Type;
const sourceProperties = getPropertiesOfObjectType(source);
if (sourceProperties) {
const sourceProperty = findSingleDiscriminantProperty(sourceProperties, target);
if (sourceProperty) {
const sourceType = getTypeOfSymbol(sourceProperty);
for (const type of target.types) {
const targetType = getTypeOfPropertyOfType(type, sourceProperty.escapedName);
if (targetType && isRelatedTo(sourceType, targetType)) {
if (match) {
return undefined;
const sourcePropertiesFiltered = findDiscriminantProperties(sourceProperties, target);
if (sourcePropertiesFiltered) {
for (const sourceProperty of sourcePropertiesFiltered) {
const sourceType = getTypeOfSymbol(sourceProperty);
for (const type of target.types) {
const targetType = getTypeOfPropertyOfType(type, sourceProperty.escapedName);
if (targetType && isRelatedTo(sourceType, targetType)) {
if (type === match) continue; // Finding multiple fields which discriminate to the same type is fine
if (match) {
return undefined;
}
match = type;
}
match = type;
}
}
}
@@ -11396,14 +11400,15 @@ namespace ts {
return false;
}
function findSingleDiscriminantProperty(sourceProperties: Symbol[], target: Type): Symbol | undefined {
let result: Symbol;
function findDiscriminantProperties(sourceProperties: Symbol[], target: Type): Symbol[] | undefined {
let result: Symbol[];
for (const sourceProperty of sourceProperties) {
if (isDiscriminantProperty(target, sourceProperty.escapedName)) {
if (result) {
return undefined;
result.push(sourceProperty);
continue;
}
result = sourceProperty;
result = [sourceProperty];
}
}
return result;
@@ -13691,8 +13696,32 @@ namespace ts {
// Return the contextual type for a given expression node. During overload resolution, a contextual type may temporarily
// be "pushed" onto a node using the contextualType property.
function getApparentTypeOfContextualType(node: Expression): Type {
const type = getContextualType(node);
return type && mapType(type, getApparentType);
let contextualType = getContextualType(node);
contextualType = contextualType && mapType(contextualType, getApparentType);
if (!(contextualType && contextualType.flags & TypeFlags.Union && isObjectLiteralExpression(node))) {
return contextualType;
}
// Keep the below up-to-date with the work done within `isRelatedTo` by `findMatchingDiscriminantType`
let match: Type | undefined;
propLoop: for (const prop of node.properties) {
if (!prop.symbol) continue;
if (prop.kind !== SyntaxKind.PropertyAssignment) continue;
if (isDiscriminantProperty(contextualType, prop.symbol.escapedName)) {
const discriminatingType = getTypeOfNode(prop.initializer);
for (const type of (contextualType as UnionType).types) {
const targetType = getTypeOfPropertyOfType(type, prop.symbol.escapedName);
if (targetType && checkTypeAssignableTo(discriminatingType, targetType, /*errorNode*/ undefined)) {
if (match) {
if (type === match) continue; // Finding multiple fields which discriminate to the same type is fine
match = undefined;
break propLoop;
}
match = type;
}
}
}
}
return match || contextualType;
}
/**