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Narrow on element access of known property #10565

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Narrow on element access of known property #10565

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c13b936
Narrow on element access of known property
sandersn Aug 26, 2016
3ca3d30
Test narrowing of element access of known property
sandersn Aug 26, 2016
d05e354
Add baselines, which I missed
sandersn Aug 26, 2016
965c4ca
Add test and TODOs for narrowing iterated accesses
sandersn Aug 29, 2016
a334e6a
Narrow nested element accesses of known properties
sandersn Aug 29, 2016
f46117f
Test nested narrowing of element accesses
sandersn Aug 29, 2016
690d799
Merge branch 'master' into narrow-on-element-access-of-known-property
sandersn Sep 1, 2016
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19 changes: 16 additions & 3 deletions src/compiler/binder.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -594,6 +594,7 @@ namespace ts {
case SyntaxKind.Identifier:
case SyntaxKind.ThisKeyword:
case SyntaxKind.PropertyAccessExpression:
case SyntaxKind.ElementAccessExpression:
return isNarrowableReference(expr);
case SyntaxKind.CallExpression:
return hasNarrowableArgument(<CallExpression>expr);
Expand All @@ -608,9 +609,20 @@ namespace ts {
}

function isNarrowableReference(expr: Expression): boolean {
return expr.kind === SyntaxKind.Identifier ||
expr.kind === SyntaxKind.ThisKeyword ||
expr.kind === SyntaxKind.PropertyAccessExpression && isNarrowableReference((<PropertyAccessExpression>expr).expression);
if (expr.kind === SyntaxKind.Identifier || expr.kind === SyntaxKind.ThisKeyword) {
return true;
}
if (expr.kind === SyntaxKind.PropertyAccessExpression) {
return isNarrowableReference((expr as PropertyAccessExpression).expression);
}
if (expr.kind === SyntaxKind.ElementAccessExpression) {
const access = expr as ElementAccessExpression;
const isArgumentLiteral = access.argumentExpression &&
(access.argumentExpression.kind === SyntaxKind.StringLiteral ||
access.argumentExpression.kind === SyntaxKind.NumericLiteral);
return isArgumentLiteral && isNarrowableReference(access.expression);
}
return false;
}

function hasNarrowableArgument(expr: CallExpression) {
Expand Down Expand Up @@ -1724,6 +1736,7 @@ namespace ts {
}
return checkStrictModeIdentifier(<Identifier>node);
case SyntaxKind.PropertyAccessExpression:
case SyntaxKind.ElementAccessExpression:
if (currentFlow && isNarrowableReference(<Expression>node)) {
node.flowNode = currentFlow;
}
Expand Down
52 changes: 36 additions & 16 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -7854,11 +7854,25 @@ namespace ts {
case SyntaxKind.ThisKeyword:
return target.kind === SyntaxKind.ThisKeyword;
case SyntaxKind.PropertyAccessExpression:
return target.kind === SyntaxKind.PropertyAccessExpression &&
(<PropertyAccessExpression>source).name.text === (<PropertyAccessExpression>target).name.text &&
isMatchingReference((<PropertyAccessExpression>source).expression, (<PropertyAccessExpression>target).expression);
case SyntaxKind.ElementAccessExpression:
if (target.kind !== SyntaxKind.PropertyAccessExpression && target.kind !== SyntaxKind.ElementAccessExpression) {
return false;
}
const sourceAccess = source as PropertyAccessExpression | ElementAccessExpression;
const targetAccess = target as PropertyAccessExpression | ElementAccessExpression;
return isMatchingReference(sourceAccess.expression, targetAccess.expression) &&
getAccessedPropertyName(sourceAccess) === getAccessedPropertyName(targetAccess);
}
return false;
}

function getAccessedPropertyName(access: PropertyAccessExpression | ElementAccessExpression, type?: Type | undefined): string {
if (!type) {
type = getTypeOfNode(access.expression);
}
return false;
return access.kind === SyntaxKind.PropertyAccessExpression ?
(access as PropertyAccessExpression).name.text :
getPropertyNameForIndexedAccess((access as ElementAccessExpression).argumentExpression, type);
}

function containsMatchingReference(source: Node, target: Node) {
Expand Down Expand Up @@ -8353,7 +8367,9 @@ namespace ts {
type = narrowTypeBySwitchOnDiscriminant(type, flow.switchStatement, flow.clauseStart, flow.clauseEnd);
}
else if (isMatchingReferenceDiscriminant(expr)) {
type = narrowTypeByDiscriminant(type, <PropertyAccessExpression>expr, t => narrowTypeBySwitchOnDiscriminant(t, flow.switchStatement, flow.clauseStart, flow.clauseEnd));
type = narrowTypeByDiscriminant(type,
expr as PropertyAccessExpression | ElementAccessExpression,
t => narrowTypeBySwitchOnDiscriminant(t, flow.switchStatement, flow.clauseStart, flow.clauseEnd));
}
return createFlowType(type, isIncomplete(flowType));
}
Expand Down Expand Up @@ -8456,14 +8472,17 @@ namespace ts {
}

function isMatchingReferenceDiscriminant(expr: Expression) {
return expr.kind === SyntaxKind.PropertyAccessExpression &&
declaredType.flags & TypeFlags.Union &&
isMatchingReference(reference, (<PropertyAccessExpression>expr).expression) &&
isDiscriminantProperty(declaredType, (<PropertyAccessExpression>expr).name.text);
if (!(declaredType.flags & TypeFlags.Union) ||
expr.kind !== SyntaxKind.PropertyAccessExpression && expr.kind !== SyntaxKind.ElementAccessExpression) {
return false;
}
const access = expr as PropertyAccessExpression | ElementAccessExpression;
const name = getAccessedPropertyName(access, declaredType);
return isMatchingReference(reference, access.expression) && isDiscriminantProperty(declaredType, name);
}

function narrowTypeByDiscriminant(type: Type, propAccess: PropertyAccessExpression, narrowType: (t: Type) => Type): Type {
const propName = propAccess.name.text;
function narrowTypeByDiscriminant(type: Type, access: PropertyAccessExpression | ElementAccessExpression, narrowType: (t: Type) => Type): Type {
const propName = getAccessedPropertyName(access, type);
const propType = getTypeOfPropertyOfType(type, propName);
const narrowedPropType = propType && narrowType(propType);
return propType === narrowedPropType ? type : filterType(type, t => isTypeComparableTo(getTypeOfPropertyOfType(t, propName), narrowedPropType));
Expand All @@ -8474,7 +8493,7 @@ namespace ts {
return getTypeWithFacts(type, assumeTrue ? TypeFacts.Truthy : TypeFacts.Falsy);
}
if (isMatchingReferenceDiscriminant(expr)) {
return narrowTypeByDiscriminant(type, <PropertyAccessExpression>expr, t => getTypeWithFacts(t, assumeTrue ? TypeFacts.Truthy : TypeFacts.Falsy));
return narrowTypeByDiscriminant(type, <PropertyAccessExpression | ElementAccessExpression>expr, t => getTypeWithFacts(t, assumeTrue ? TypeFacts.Truthy : TypeFacts.Falsy));
}
if (containsMatchingReferenceDiscriminant(reference, expr)) {
return declaredType;
Expand Down Expand Up @@ -8506,10 +8525,10 @@ namespace ts {
return narrowTypeByEquality(type, operator, left, assumeTrue);
}
if (isMatchingReferenceDiscriminant(left)) {
return narrowTypeByDiscriminant(type, <PropertyAccessExpression>left, t => narrowTypeByEquality(t, operator, right, assumeTrue));
return narrowTypeByDiscriminant(type, <PropertyAccessExpression | ElementAccessExpression>left, t => narrowTypeByEquality(t, operator, right, assumeTrue));
}
if (isMatchingReferenceDiscriminant(right)) {
return narrowTypeByDiscriminant(type, <PropertyAccessExpression>right, t => narrowTypeByEquality(t, operator, left, assumeTrue));
return narrowTypeByDiscriminant(type, <PropertyAccessExpression | ElementAccessExpression>right, t => narrowTypeByEquality(t, operator, left, assumeTrue));
}
if (containsMatchingReferenceDiscriminant(reference, left) || containsMatchingReferenceDiscriminant(reference, right)) {
return declaredType;
Expand Down Expand Up @@ -10930,7 +10949,7 @@ namespace ts {
const prop = getPropertyOfType(objectType, name);
if (prop) {
getNodeLinks(node).resolvedSymbol = prop;
return getTypeOfSymbol(prop);
return getFlowTypeOfReference(node, getTypeOfSymbol(prop), /*assumeInitialized*/ true, /*flowContainer*/ undefined);
}
else if (isConstEnum) {
error(node.argumentExpression, Diagnostics.Property_0_does_not_exist_on_const_enum_1, name, symbolToString(objectType.symbol));
Expand Down Expand Up @@ -14030,7 +14049,8 @@ namespace ts {
for (const decl of indexSymbol.declarations) {
const declaration = <SignatureDeclaration>decl;
if (declaration.parameters.length === 1 && declaration.parameters[0].type) {
switch (declaration.parameters[0].type.kind) {
const workaround = 0;
switch (declaration.parameters[workaround].type.kind) {
case SyntaxKind.StringKeyword:
if (!seenStringIndexer) {
seenStringIndexer = true;
Expand Down
59 changes: 59 additions & 0 deletions tests/baselines/reference/typeGuardNarrowsIndexedAccessOfKnownProperty.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,59 @@
//// [typeGuardNarrowsIndexedAccessOfKnownProperty.ts]
interface Square {
kind: "square";
size: number;
}

interface Rectangle {
kind: "rectangle";
width: number;
height: number;
}

interface Circle {
kind: "circle";
radius: number;
}

type Shape = Square | Rectangle | Circle;
interface Subshape {
"0": {
sub: {
under: {
shape: Shape;
}
}
}
}
function area(s: Shape): number {
switch(s['kind']) {
case "square": return s.size * s.size;
case "rectangle": return s.width * s.height;
case "circle": return Math.PI * s.radius * s.radius;
}
}

function subarea(s: Subshape): number {
switch(s[0]["sub"].under["shape"]["kind"]) {
case "square": return s[0].sub.under.shape.size * s[0].sub.under.shape.size;
case "rectangle": return s[0]["sub"]["under"]["shape"]["width"] * s[0]["sub"]["under"]["shape"].height;
case "circle": return Math.PI * s[0].sub.under["shape"].radius * s[0]["sub"].under.shape["radius"];
}
}


//// [typeGuardNarrowsIndexedAccessOfKnownProperty.js]
function area(s) {
switch (s['kind']) {
case "square": return s.size * s.size;
case "rectangle": return s.width * s.height;
case "circle": return Math.PI * s.radius * s.radius;
}
}
function subarea(s) {
switch (s[0]["sub"].under["shape"]["kind"]) {
case "square": return s[0].sub.under.shape.size * s[0].sub.under.shape.size;
case "rectangle": return s[0]["sub"]["under"]["shape"]["width"] * s[0]["sub"]["under"]["shape"].height;
case "circle": return Math.PI * s[0].sub.under["shape"].radius * s[0]["sub"].under.shape["radius"];
}
}
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