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Merge pull request #9031 from Microsoft/typeGuardIntersectionTypes
Type guard intersection types
2 parents c14d711 + b1a7498 commit 9e12290

12 files changed

+922
-23
lines changed

‎src/compiler/checker.ts

+1-1
Original file line numberDiff line numberDiff line change
@@ -8007,7 +8007,7 @@ namespace ts {
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const targetType = type.flags & TypeFlags.TypeParameter ? getApparentType(type) : type;
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return isTypeAssignableTo(candidate, targetType) ? candidate :
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isTypeAssignableTo(type, candidate) ? type :
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neverType;
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getIntersectionType([type, candidate]);
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}
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function narrowTypeByTypePredicate(type: Type, callExpression: CallExpression, assumeTrue: boolean): Type {

‎tests/baselines/reference/instanceOfAssignability.types

+2-2
Original file line numberDiff line numberDiff line change
@@ -133,8 +133,8 @@ function fn5(x: Derived1) {
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// 1.5: y: Derived1
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// Want: ???
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let y = x;
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>y : never
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>x : never
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>y : Derived1 & Derived2
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>x : Derived1 & Derived2
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}
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}
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‎tests/baselines/reference/stringLiteralTypesAsTags01.types

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Original file line numberDiff line numberDiff line change
@@ -116,6 +116,6 @@ if (!hasKind(x, "B")) {
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}
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else {
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let d = x;
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>d : never
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>x : never
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>d : A & B
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>x : A & B
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}

‎tests/baselines/reference/stringLiteralTypesAsTags02.types

+2-2
Original file line numberDiff line numberDiff line change
@@ -110,6 +110,6 @@ if (!hasKind(x, "B")) {
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}
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else {
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let d = x;
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>d : never
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>x : never
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>d : A & B
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>x : A & B
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}

‎tests/baselines/reference/stringLiteralTypesAsTags03.types

+2-2
Original file line numberDiff line numberDiff line change
@@ -113,6 +113,6 @@ if (!hasKind(x, "B")) {
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}
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else {
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let d = x;
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>d : never
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>x : never
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>d : A & B
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>x : A & B
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}

‎tests/baselines/reference/typeGuardIntersectionTypes.js

+179
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,179 @@
1+
//// [typeGuardIntersectionTypes.ts]
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interface X {
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x: string;
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}
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interface Y {
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y: string;
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}
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interface Z {
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z: string;
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}
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declare function isX(obj: any): obj is X;
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declare function isY(obj: any): obj is Y;
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declare function isZ(obj: any): obj is Z;
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function f1(obj: Object) {
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if (isX(obj) || isY(obj) || isZ(obj)) {
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obj;
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}
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if (isX(obj) && isY(obj) && isZ(obj)) {
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obj;
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}
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}
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// Repro from #8911
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// two interfaces
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interface A {
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a: string;
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}
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interface B {
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b: string;
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}
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// a type guard for B
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function isB(toTest: any): toTest is B {
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return toTest && toTest.b;
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}
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// a function that turns an A into an A & B
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function union(a: A): A & B | null {
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if (isB(a)) {
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return a;
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} else {
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return null;
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}
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}
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// Repro from #9016
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declare function log(s: string): void;
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// Supported beast features
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interface Beast { wings?: boolean; legs?: number }
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interface Legged { legs: number; }
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interface Winged { wings: boolean; }
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// Beast feature detection via user-defined type guards
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function hasLegs(x: Beast): x is Legged { return x && typeof x.legs === 'number'; }
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function hasWings(x: Beast): x is Winged { return x && !!x.wings; }
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// Function to identify a given beast by detecting its features
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function identifyBeast(beast: Beast) {
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// All beasts with legs
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if (hasLegs(beast)) {
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// All winged beasts with legs
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if (hasWings(beast)) {
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if (beast.legs === 4) {
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log(`pegasus - 4 legs, wings`);
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}
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else if (beast.legs === 2) {
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log(`bird - 2 legs, wings`);
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}
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else {
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log(`unknown - ${beast.legs} legs, wings`);
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}
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}
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// All non-winged beasts with legs
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else {
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log(`manbearpig - ${beast.legs} legs, no wings`);
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}
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}
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// All beasts without legs
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else {
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if (hasWings(beast)) {
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log(`quetzalcoatl - no legs, wings`)
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}
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else {
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log(`snake - no legs, no wings`)
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}
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}
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}
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function beastFoo(beast: Object) {
103+
if (hasWings(beast) && hasLegs(beast)) {
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beast; // Winged & Legged
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}
106+
else {
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beast;
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}
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if (hasLegs(beast) && hasWings(beast)) {
111+
beast; // Legged & Winged
112+
}
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}
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//// [typeGuardIntersectionTypes.js]
116+
function f1(obj) {
117+
if (isX(obj) || isY(obj) || isZ(obj)) {
118+
obj;
119+
}
120+
if (isX(obj) && isY(obj) && isZ(obj)) {
121+
obj;
122+
}
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}
124+
// a type guard for B
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function isB(toTest) {
126+
return toTest && toTest.b;
127+
}
128+
// a function that turns an A into an A & B
129+
function union(a) {
130+
if (isB(a)) {
131+
return a;
132+
}
133+
else {
134+
return null;
135+
}
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}
137+
// Beast feature detection via user-defined type guards
138+
function hasLegs(x) { return x && typeof x.legs === 'number'; }
139+
function hasWings(x) { return x && !!x.wings; }
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// Function to identify a given beast by detecting its features
141+
function identifyBeast(beast) {
142+
// All beasts with legs
143+
if (hasLegs(beast)) {
144+
// All winged beasts with legs
145+
if (hasWings(beast)) {
146+
if (beast.legs === 4) {
147+
log("pegasus - 4 legs, wings");
148+
}
149+
else if (beast.legs === 2) {
150+
log("bird - 2 legs, wings");
151+
}
152+
else {
153+
log("unknown - " + beast.legs + " legs, wings");
154+
}
155+
}
156+
else {
157+
log("manbearpig - " + beast.legs + " legs, no wings");
158+
}
159+
}
160+
else {
161+
if (hasWings(beast)) {
162+
log("quetzalcoatl - no legs, wings");
163+
}
164+
else {
165+
log("snake - no legs, no wings");
166+
}
167+
}
168+
}
169+
function beastFoo(beast) {
170+
if (hasWings(beast) && hasLegs(beast)) {
171+
beast; // Winged & Legged
172+
}
173+
else {
174+
beast;
175+
}
176+
if (hasLegs(beast) && hasWings(beast)) {
177+
beast; // Legged & Winged
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}
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}

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