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Add initial support for 'in' typeguarding
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9 files changed

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‎src/compiler/binder.ts

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@@ -749,6 +749,10 @@ namespace ts {
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return expr1.kind === SyntaxKind.TypeOfExpression && isNarrowableOperand((<TypeOfExpression>expr1).expression) && expr2.kind === SyntaxKind.StringLiteral;
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}
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function isNarrowableInOperands(left: Expression, right: Expression) {
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return left.kind === SyntaxKind.StringLiteral && isNarrowingExpression(right);
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}
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function isNarrowingBinaryExpression(expr: BinaryExpression) {
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switch (expr.operatorToken.kind) {
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case SyntaxKind.EqualsToken:
@@ -761,6 +765,8 @@ namespace ts {
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isNarrowingTypeofOperands(expr.right, expr.left) || isNarrowingTypeofOperands(expr.left, expr.right);
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case SyntaxKind.InstanceOfKeyword:
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return isNarrowableOperand(expr.left);
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case SyntaxKind.InKeyword:
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return isNarrowableInOperands(expr.left, expr.right);
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case SyntaxKind.CommaToken:
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return isNarrowingExpression(expr.right);
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}

‎src/compiler/checker.ts

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@@ -12722,6 +12722,14 @@ namespace ts {
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return type;
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}
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function narrowByInKeyword(type: Type, literal: LiteralExpression, assumeTrue: boolean) {
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if ((type.flags & (TypeFlags.Union | TypeFlags.Object)) || (type.flags & TypeFlags.TypeParameter && (type as TypeParameter).isThisType)) {
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const propName = literal.text;
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return filterType(type, t => !!getPropertyOfType(t, propName) === assumeTrue);
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}
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return type;
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}
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function narrowTypeByBinaryExpression(type: Type, expr: BinaryExpression, assumeTrue: boolean): Type {
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switch (expr.operatorToken.kind) {
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case SyntaxKind.EqualsToken:
@@ -12757,6 +12765,12 @@ namespace ts {
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break;
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case SyntaxKind.InstanceOfKeyword:
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return narrowTypeByInstanceof(type, expr, assumeTrue);
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case SyntaxKind.InKeyword:
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const target = getReferenceCandidate(expr.right);
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if (expr.left.kind === SyntaxKind.StringLiteral && isMatchingReference(reference, target)) {
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return narrowByInKeyword(type, <LiteralExpression>expr.left, assumeTrue);
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}
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break;
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case SyntaxKind.CommaToken:
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return narrowType(type, expr.right, assumeTrue);
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}

‎tests/baselines/reference/inKeywordTypeguard.errors.txt

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@@ -0,0 +1,154 @@
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tests/cases/compiler/inKeywordTypeguard.ts(6,11): error TS2339: Property 'b' does not exist on type 'A'.
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tests/cases/compiler/inKeywordTypeguard.ts(8,11): error TS2339: Property 'a' does not exist on type 'B'.
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tests/cases/compiler/inKeywordTypeguard.ts(14,11): error TS2339: Property 'b' does not exist on type 'A'.
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tests/cases/compiler/inKeywordTypeguard.ts(16,11): error TS2339: Property 'a' does not exist on type 'B'.
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tests/cases/compiler/inKeywordTypeguard.ts(42,11): error TS2339: Property 'b' does not exist on type 'AWithMethod'.
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tests/cases/compiler/inKeywordTypeguard.ts(49,11): error TS2339: Property 'a' does not exist on type 'never'.
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tests/cases/compiler/inKeywordTypeguard.ts(50,11): error TS2339: Property 'b' does not exist on type 'never'.
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tests/cases/compiler/inKeywordTypeguard.ts(52,11): error TS2339: Property 'a' does not exist on type 'AWithMethod | BWithMethod'.
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Property 'a' does not exist on type 'BWithMethod'.
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tests/cases/compiler/inKeywordTypeguard.ts(53,11): error TS2339: Property 'b' does not exist on type 'AWithMethod | BWithMethod'.
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Property 'b' does not exist on type 'AWithMethod'.
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tests/cases/compiler/inKeywordTypeguard.ts(62,11): error TS2339: Property 'b' does not exist on type 'A | C | D'.
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Property 'b' does not exist on type 'A'.
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tests/cases/compiler/inKeywordTypeguard.ts(64,11): error TS2339: Property 'a' does not exist on type 'B'.
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tests/cases/compiler/inKeywordTypeguard.ts(72,32): error TS2339: Property 'b' does not exist on type 'A'.
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tests/cases/compiler/inKeywordTypeguard.ts(74,32): error TS2339: Property 'a' does not exist on type 'B'.
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tests/cases/compiler/inKeywordTypeguard.ts(82,39): error TS2339: Property 'b' does not exist on type 'A'.
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tests/cases/compiler/inKeywordTypeguard.ts(84,39): error TS2339: Property 'a' does not exist on type 'B'.
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tests/cases/compiler/inKeywordTypeguard.ts(94,26): error TS2339: Property 'a' does not exist on type 'never'.
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==== tests/cases/compiler/inKeywordTypeguard.ts (16 errors) ====
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class A { a: string; }
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class B { b: string; }
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function negativeClassesTest(x: A | B) {
27+
if ("a" in x) {
28+
x.b = "1";
29+
~
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!!! error TS2339: Property 'b' does not exist on type 'A'.
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} else {
32+
x.a = "1";
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~
34+
!!! error TS2339: Property 'a' does not exist on type 'B'.
35+
}
36+
}
37+
38+
function positiveClassesTest(x: A | B) {
39+
if ("a" in x) {
40+
x.b = "1";
41+
~
42+
!!! error TS2339: Property 'b' does not exist on type 'A'.
43+
} else {
44+
x.a = "1";
45+
~
46+
!!! error TS2339: Property 'a' does not exist on type 'B'.
47+
}
48+
}
49+
50+
class AOpt { a?: string }
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class BOpn { b?: string }
52+
53+
function positiveTestClassesWithOptionalProperties(x: AOpt | BOpn) {
54+
if ("a" in x) {
55+
x.a = "1";
56+
} else {
57+
x.b = "1";
58+
}
59+
}
60+
61+
class AWithMethod {
62+
a(): string { return "" }
63+
}
64+
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class BWithMethod {
66+
b(): string { return "" }
67+
}
68+
69+
function negativeTestClassesWithMembers(x: AWithMethod | BWithMethod) {
70+
if ("a" in x) {
71+
x.a();
72+
x.b();
73+
~
74+
!!! error TS2339: Property 'b' does not exist on type 'AWithMethod'.
75+
} else {
76+
}
77+
}
78+
79+
function negativeTestClassesWithMemberMissingInBothClasses(x: AWithMethod | BWithMethod) {
80+
if ("c" in x) {
81+
x.a();
82+
~
83+
!!! error TS2339: Property 'a' does not exist on type 'never'.
84+
x.b();
85+
~
86+
!!! error TS2339: Property 'b' does not exist on type 'never'.
87+
} else {
88+
x.a();
89+
~
90+
!!! error TS2339: Property 'a' does not exist on type 'AWithMethod | BWithMethod'.
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!!! error TS2339: Property 'a' does not exist on type 'BWithMethod'.
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x.b();
93+
~
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!!! error TS2339: Property 'b' does not exist on type 'AWithMethod | BWithMethod'.
95+
!!! error TS2339: Property 'b' does not exist on type 'AWithMethod'.
96+
}
97+
}
98+
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class C { a: string }
100+
class D { a: string }
101+
102+
function negativeMultipleClassesTest(x: A | B | C | D) {
103+
if ("a" in x) {
104+
x.b = "1";
105+
~
106+
!!! error TS2339: Property 'b' does not exist on type 'A | C | D'.
107+
!!! error TS2339: Property 'b' does not exist on type 'A'.
108+
} else {
109+
x.a = "1";
110+
~
111+
!!! error TS2339: Property 'a' does not exist on type 'B'.
112+
}
113+
}
114+
115+
class ClassWithProp { prop: A | B }
116+
117+
function negativePropTest(x: ClassWithProp) {
118+
if ("a" in x.prop) {
119+
let y: string = x.prop.b;
120+
~
121+
!!! error TS2339: Property 'b' does not exist on type 'A'.
122+
} else {
123+
let z: string = x.prop.a;
124+
~
125+
!!! error TS2339: Property 'a' does not exist on type 'B'.
126+
}
127+
}
128+
129+
class NegativeClassTest {
130+
protected prop: A | B;
131+
inThis() {
132+
if ('a' in this.prop) {
133+
let z: number = this.prop.b;
134+
~
135+
!!! error TS2339: Property 'b' does not exist on type 'A'.
136+
} else {
137+
let y: string = this.prop.a;
138+
~
139+
!!! error TS2339: Property 'a' does not exist on type 'B'.
140+
}
141+
}
142+
}
143+
144+
class UnreachableCodeDetection {
145+
a: string;
146+
inThis() {
147+
if ('a' in this) {
148+
} else {
149+
let y = this.a;
150+
~
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!!! error TS2339: Property 'a' does not exist on type 'never'.
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}
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}
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}

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