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Weaker narrowing for ==
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6 files changed

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6 files changed

+506
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‎src/compiler/checker.ts

Lines changed: 30 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -13795,6 +13795,32 @@ namespace ts {
1379513795
return strictNullChecks ? getGlobalNonNullableTypeInstantiation(type) : type;
1379613796
}
1379713797

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/**
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* Is source potentially coercible to target type under `==`.
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* Assumes that `source` is a constituent of a union, hence
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* the boolean literal flag on the LHS, but not on the RHS.
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*
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* This does not fully replicate the semantics of `==`. The
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* intention is to catch cases that are clearly not right.
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*
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* Comparing (string | number) to number should not remove the
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* string element.
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*
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* Comparing (string | number) to 1 will remove the string
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* element, though this is not sound. This is a pragmatic
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* choice.
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*
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* @see narrowTypeByEquality
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*
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* @param source
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* @param target
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*/
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function isCoercibleUnderDoubleEquals(source: Type, target: Type): boolean {
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return ((source.flags & (TypeFlags.Number | TypeFlags.String | TypeFlags.BooleanLiteral)) !== 0)
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&& ((target.flags & (TypeFlags.Number | TypeFlags.String | TypeFlags.Boolean)) !== 0);
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}
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1379813824
/**
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* Return true if type was inferred from an object literal, written as an object type literal, or is the shape of a module
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* with no call or construct signatures.
@@ -16101,7 +16127,10 @@ namespace ts {
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return type;
1610216128
}
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if (assumeTrue) {
16104-
const narrowedType = filterType(type, t => areTypesComparable(t, valueType));
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const filterFn: (t: Type) => boolean = operator === SyntaxKind.EqualsEqualsToken ?
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(t => areTypesComparable(t, valueType) || isCoercibleUnderDoubleEquals(t, valueType)) :
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t => areTypesComparable(t, valueType);
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const narrowedType = filterType(type, filterFn);
1610516134
return narrowedType.flags & TypeFlags.Never ? type : replacePrimitivesWithLiterals(narrowedType, valueType);
1610616135
}
1610716136
if (isUnitType(valueType)) {

‎tests/baselines/reference/narrowByEquality.errors.txt

Lines changed: 71 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,71 @@
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tests/cases/compiler/narrowByEquality.ts(53,15): error TS2322: Type 'string | number' is not assignable to type 'number'.
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Type 'string' is not assignable to type 'number'.
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tests/cases/compiler/narrowByEquality.ts(54,9): error TS2322: Type 'string | number' is not assignable to type 'number'.
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Type 'string' is not assignable to type 'number'.
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6+
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==== tests/cases/compiler/narrowByEquality.ts (2 errors) ====
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declare let x: number | string | boolean
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declare let n: number;
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declare let s: string;
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declare let b: boolean;
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if (x == n) {
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x;
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}
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if (x == s) {
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x;
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}
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if (x == b) {
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x;
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}
24+
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if (x == 1) {
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x;
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}
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if (x == "") {
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x;
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}
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if (x == "foo") {
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x;
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}
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if (x == true) {
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x;
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}
40+
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if (x == false) {
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x;
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}
44+
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declare let xAndObj: number | string | boolean | object
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if (xAndObj == {}) {
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xAndObj;
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}
50+
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if (x == xAndObj) {
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x;
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xAndObj;
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}
55+
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// Repro from #24991
57+
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function test(level: number | string):number {
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if (level == +level) {
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const q2: number = level; // error
61+
~~
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!!! error TS2322: Type 'string | number' is not assignable to type 'number'.
63+
!!! error TS2322: Type 'string' is not assignable to type 'number'.
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return level;
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~~~~~~~~~~~~~
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!!! error TS2322: Type 'string | number' is not assignable to type 'number'.
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!!! error TS2322: Type 'string' is not assignable to type 'number'.
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}
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return 0;
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}
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‎tests/baselines/reference/narrowByEquality.js

Lines changed: 101 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,101 @@
1+
//// [narrowByEquality.ts]
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declare let x: number | string | boolean
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declare let n: number;
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declare let s: string;
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declare let b: boolean;
6+
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if (x == n) {
8+
x;
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}
10+
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if (x == s) {
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x;
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}
14+
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if (x == b) {
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x;
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}
18+
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if (x == 1) {
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x;
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}
22+
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if (x == "") {
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x;
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}
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if (x == "foo") {
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x;
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}
30+
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if (x == true) {
32+
x;
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}
34+
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if (x == false) {
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x;
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}
38+
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declare let xAndObj: number | string | boolean | object
40+
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if (xAndObj == {}) {
42+
xAndObj;
43+
}
44+
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if (x == xAndObj) {
46+
x;
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xAndObj;
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}
49+
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// Repro from #24991
51+
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function test(level: number | string):number {
53+
if (level == +level) {
54+
const q2: number = level; // error
55+
return level;
56+
}
57+
return 0;
58+
}
59+
60+
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//// [narrowByEquality.js]
62+
"use strict";
63+
if (x == n) {
64+
x;
65+
}
66+
if (x == s) {
67+
x;
68+
}
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if (x == b) {
70+
x;
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}
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if (x == 1) {
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x;
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}
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if (x == "") {
76+
x;
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}
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if (x == "foo") {
79+
x;
80+
}
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if (x == true) {
82+
x;
83+
}
84+
if (x == false) {
85+
x;
86+
}
87+
if (xAndObj == {}) {
88+
xAndObj;
89+
}
90+
if (x == xAndObj) {
91+
x;
92+
xAndObj;
93+
}
94+
// Repro from #24991
95+
function test(level) {
96+
if (level == +level) {
97+
var q2 = level; // error
98+
return level;
99+
}
100+
return 0;
101+
}

‎tests/baselines/reference/narrowByEquality.symbols

Lines changed: 113 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,113 @@
1+
=== tests/cases/compiler/narrowByEquality.ts ===
2+
declare let x: number | string | boolean
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>x : Symbol(x, Decl(narrowByEquality.ts, 0, 11))
4+
5+
declare let n: number;
6+
>n : Symbol(n, Decl(narrowByEquality.ts, 1, 11))
7+
8+
declare let s: string;
9+
>s : Symbol(s, Decl(narrowByEquality.ts, 2, 11))
10+
11+
declare let b: boolean;
12+
>b : Symbol(b, Decl(narrowByEquality.ts, 3, 11))
13+
14+
if (x == n) {
15+
>x : Symbol(x, Decl(narrowByEquality.ts, 0, 11))
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>n : Symbol(n, Decl(narrowByEquality.ts, 1, 11))
17+
18+
x;
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>x : Symbol(x, Decl(narrowByEquality.ts, 0, 11))
20+
}
21+
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if (x == s) {
23+
>x : Symbol(x, Decl(narrowByEquality.ts, 0, 11))
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>s : Symbol(s, Decl(narrowByEquality.ts, 2, 11))
25+
26+
x;
27+
>x : Symbol(x, Decl(narrowByEquality.ts, 0, 11))
28+
}
29+
30+
if (x == b) {
31+
>x : Symbol(x, Decl(narrowByEquality.ts, 0, 11))
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>b : Symbol(b, Decl(narrowByEquality.ts, 3, 11))
33+
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x;
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>x : Symbol(x, Decl(narrowByEquality.ts, 0, 11))
36+
}
37+
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if (x == 1) {
39+
>x : Symbol(x, Decl(narrowByEquality.ts, 0, 11))
40+
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x;
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>x : Symbol(x, Decl(narrowByEquality.ts, 0, 11))
43+
}
44+
45+
if (x == "") {
46+
>x : Symbol(x, Decl(narrowByEquality.ts, 0, 11))
47+
48+
x;
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>x : Symbol(x, Decl(narrowByEquality.ts, 0, 11))
50+
}
51+
52+
if (x == "foo") {
53+
>x : Symbol(x, Decl(narrowByEquality.ts, 0, 11))
54+
55+
x;
56+
>x : Symbol(x, Decl(narrowByEquality.ts, 0, 11))
57+
}
58+
59+
if (x == true) {
60+
>x : Symbol(x, Decl(narrowByEquality.ts, 0, 11))
61+
62+
x;
63+
>x : Symbol(x, Decl(narrowByEquality.ts, 0, 11))
64+
}
65+
66+
if (x == false) {
67+
>x : Symbol(x, Decl(narrowByEquality.ts, 0, 11))
68+
69+
x;
70+
>x : Symbol(x, Decl(narrowByEquality.ts, 0, 11))
71+
}
72+
73+
declare let xAndObj: number | string | boolean | object
74+
>xAndObj : Symbol(xAndObj, Decl(narrowByEquality.ts, 37, 11))
75+
76+
if (xAndObj == {}) {
77+
>xAndObj : Symbol(xAndObj, Decl(narrowByEquality.ts, 37, 11))
78+
79+
xAndObj;
80+
>xAndObj : Symbol(xAndObj, Decl(narrowByEquality.ts, 37, 11))
81+
}
82+
83+
if (x == xAndObj) {
84+
>x : Symbol(x, Decl(narrowByEquality.ts, 0, 11))
85+
>xAndObj : Symbol(xAndObj, Decl(narrowByEquality.ts, 37, 11))
86+
87+
x;
88+
>x : Symbol(x, Decl(narrowByEquality.ts, 0, 11))
89+
90+
xAndObj;
91+
>xAndObj : Symbol(xAndObj, Decl(narrowByEquality.ts, 37, 11))
92+
}
93+
94+
// Repro from #24991
95+
96+
function test(level: number | string):number {
97+
>test : Symbol(test, Decl(narrowByEquality.ts, 46, 1))
98+
>level : Symbol(level, Decl(narrowByEquality.ts, 50, 14))
99+
100+
if (level == +level) {
101+
>level : Symbol(level, Decl(narrowByEquality.ts, 50, 14))
102+
>level : Symbol(level, Decl(narrowByEquality.ts, 50, 14))
103+
104+
const q2: number = level; // error
105+
>q2 : Symbol(q2, Decl(narrowByEquality.ts, 52, 13))
106+
>level : Symbol(level, Decl(narrowByEquality.ts, 50, 14))
107+
108+
return level;
109+
>level : Symbol(level, Decl(narrowByEquality.ts, 50, 14))
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}
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return 0;
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}
113+

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