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Remove CFA discriminant check restrictions #36114

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Merged
merged 2 commits into from
Jan 10, 2020
Merged

Remove CFA discriminant check restrictions #36114

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abe4323
Remove unnecessary containsMatchingReferenceDiscriminant logic
ahejlsberg Jan 10, 2020
766cb83
Accept new baselines
ahejlsberg Jan 10, 2020
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38 changes: 0 additions & 38 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -18452,32 +18452,6 @@ namespace ts {
return false;
}

// Return true if target is a property access xxx.yyy, source is a property access xxx.zzz, the declared
// type of xxx is a union type, and yyy is a property that is possibly a discriminant. We consider a property
// a possible discriminant if its type differs in the constituents of containing union type, and if every
// choice is a unit type or a union of unit types.
function containsMatchingReferenceDiscriminant(source: Node, target: Node) {
let name;
return isAccessExpression(target) &&
containsMatchingReference(source, target.expression) &&
(name = getAccessedPropertyName(target)) !== undefined &&
isDiscriminantProperty(getDeclaredTypeOfReference(target.expression), name);
}

function getDeclaredTypeOfReference(expr: Node): Type | undefined {
if (expr.kind === SyntaxKind.Identifier) {
return getTypeOfSymbol(getResolvedSymbol(<Identifier>expr));
}
if (isAccessExpression(expr)) {
const type = getDeclaredTypeOfReference(expr.expression);
if (type) {
const propName = getAccessedPropertyName(expr);
return propName !== undefined ? getTypeOfPropertyOfType(type, propName) : undefined;
}
}
return undefined;
}

function isDiscriminantProperty(type: Type | undefined, name: __String) {
if (type && type.flags & TypeFlags.Union) {
const prop = getUnionOrIntersectionProperty(<UnionType>type, name);
Expand Down Expand Up @@ -19509,9 +19483,6 @@ namespace ts {
type = narrowTypeByDiscriminant(type, expr as AccessExpression,
t => narrowTypeBySwitchOnDiscriminant(t, flow.switchStatement, flow.clauseStart, flow.clauseEnd));
}
else if (containsMatchingReferenceDiscriminant(reference, expr)) {
type = declaredType;
}
}
return createFlowType(type, isIncomplete(flowType));
}
Expand Down Expand Up @@ -19696,9 +19667,6 @@ namespace ts {
if (isMatchingReferenceDiscriminant(expr, declaredType)) {
return narrowTypeByDiscriminant(type, <AccessExpression>expr, t => getTypeWithFacts(t, assumeTrue ? TypeFacts.Truthy : TypeFacts.Falsy));
}
if (containsMatchingReferenceDiscriminant(reference, expr)) {
return declaredType;
}
return type;
}

Expand Down Expand Up @@ -19758,9 +19726,6 @@ namespace ts {
if (isMatchingReferenceDiscriminant(right, declaredType)) {
return narrowTypeByDiscriminant(type, <AccessExpression>right, t => narrowTypeByEquality(t, operator, left, assumeTrue));
}
if (containsMatchingReferenceDiscriminant(reference, left) || containsMatchingReferenceDiscriminant(reference, right)) {
return declaredType;
}
break;
case SyntaxKind.InstanceOfKeyword:
return narrowTypeByInstanceof(type, expr, assumeTrue);
Expand Down Expand Up @@ -20172,9 +20137,6 @@ namespace ts {
if (isMatchingReferenceDiscriminant(expr, declaredType)) {
return narrowTypeByDiscriminant(type, <AccessExpression>expr, t => getTypeWithFacts(t, assumePresent ? TypeFacts.NEUndefinedOrNull : TypeFacts.EQUndefinedOrNull));
}
if (containsMatchingReferenceDiscriminant(reference, expr)) {
return declaredType;
}
return type;
}
}
Expand Down
185 changes: 0 additions & 185 deletions tests/baselines/reference/discriminantPropertyCheck.errors.txt
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8 changes: 4 additions & 4 deletions tests/baselines/reference/discriminantPropertyCheck.types
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Original file line number Diff line number Diff line change
Expand Up @@ -82,9 +82,9 @@ function goo2(x: Item) {

x.foo.length; // Error, intervening discriminant guard
>x.foo.length : number
>x.foo : string | undefined
>x.foo : string
>x : Item1
>foo : string | undefined
>foo : string
>length : number
}
}
Expand Down Expand Up @@ -226,9 +226,9 @@ function foo6(x: Item) {

x.foo.length; // Error, intervening discriminant guard
>x.foo.length : number
>x.foo : string | undefined
>x.foo : string
>x : Item1
>foo : string | undefined
>foo : string
>length : number
}
}
Expand Down