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mattmccutchenmattmccutchen
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Remove the rule that replaces a union of literal types with the base
type when comparing equality to a type that isn't a union of literal types. The rule is redundant because a primitive type is already directed- comparable to a value of that primitive type, and it causes errors to be missed when comparing a type parameter _constrained_ by a union of literal types to another union of literal types. The baseline changes look like improvements to me. Fixes #26758.
1 parent bbf559b commit 112fa23

12 files changed

Lines changed: 110 additions & 24 deletions

‎src/compiler/checker.ts‎

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Original file line numberDiff line numberDiff line change
@@ -22832,12 +22832,6 @@ namespace ts {
2283222832
case SyntaxKind.ExclamationEqualsToken:
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case SyntaxKind.EqualsEqualsEqualsToken:
2283422834
case SyntaxKind.ExclamationEqualsEqualsToken:
22835-
const leftIsLiteral = isLiteralType(leftType);
22836-
const rightIsLiteral = isLiteralType(rightType);
22837-
if (!leftIsLiteral || !rightIsLiteral) {
22838-
leftType = leftIsLiteral ? getBaseTypeOfLiteralType(leftType) : leftType;
22839-
rightType = rightIsLiteral ? getBaseTypeOfLiteralType(rightType) : rightType;
22840-
}
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if (!isTypeEqualityComparableTo(leftType, rightType) && !isTypeEqualityComparableTo(rightType, leftType)) {
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reportOperatorError();
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}

‎tests/baselines/reference/compareTypeParameterConstrainedByLiteralToLiteral.errors.txt‎

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@@ -0,0 +1,13 @@
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tests/cases/compiler/compareTypeParameterConstrainedByLiteralToLiteral.ts(5,5): error TS2367: This condition will always return 'false' since the types 'T' and '"x"' have no overlap.
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4+
==== tests/cases/compiler/compareTypeParameterConstrainedByLiteralToLiteral.ts (1 errors) ====
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// Test for #26758
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7+
function foo<T extends "a" | "b">(t: T) {
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t === "a"; // Should be allowed
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t === "x"; // Should be error
10+
~~~~~~~~~
11+
!!! error TS2367: This condition will always return 'false' since the types 'T' and '"x"' have no overlap.
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}
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‎tests/baselines/reference/compareTypeParameterConstrainedByLiteralToLiteral.js‎

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@@ -0,0 +1,15 @@
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//// [compareTypeParameterConstrainedByLiteralToLiteral.ts]
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// Test for #26758
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function foo<T extends "a" | "b">(t: T) {
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t === "a"; // Should be allowed
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t === "x"; // Should be error
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}
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10+
//// [compareTypeParameterConstrainedByLiteralToLiteral.js]
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// Test for #26758
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function foo(t) {
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t === "a"; // Should be allowed
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t === "x"; // Should be error
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}

‎tests/baselines/reference/compareTypeParameterConstrainedByLiteralToLiteral.symbols‎

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@@ -0,0 +1,16 @@
1+
=== tests/cases/compiler/compareTypeParameterConstrainedByLiteralToLiteral.ts ===
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// Test for #26758
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function foo<T extends "a" | "b">(t: T) {
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>foo : Symbol(foo, Decl(compareTypeParameterConstrainedByLiteralToLiteral.ts, 0, 0))
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>T : Symbol(T, Decl(compareTypeParameterConstrainedByLiteralToLiteral.ts, 2, 13))
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>t : Symbol(t, Decl(compareTypeParameterConstrainedByLiteralToLiteral.ts, 2, 34))
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>T : Symbol(T, Decl(compareTypeParameterConstrainedByLiteralToLiteral.ts, 2, 13))
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t === "a"; // Should be allowed
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>t : Symbol(t, Decl(compareTypeParameterConstrainedByLiteralToLiteral.ts, 2, 34))
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t === "x"; // Should be error
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>t : Symbol(t, Decl(compareTypeParameterConstrainedByLiteralToLiteral.ts, 2, 34))
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}
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‎tests/baselines/reference/compareTypeParameterConstrainedByLiteralToLiteral.types‎

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@@ -0,0 +1,18 @@
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=== tests/cases/compiler/compareTypeParameterConstrainedByLiteralToLiteral.ts ===
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// Test for #26758
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function foo<T extends "a" | "b">(t: T) {
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>foo : <T extends "a" | "b">(t: T) => void
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>t : T
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t === "a"; // Should be allowed
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>t === "a" : boolean
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>t : T
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>"a" : "a"
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t === "x"; // Should be error
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>t === "x" : boolean
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>t : T
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>"x" : "x"
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}
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‎tests/baselines/reference/expr.errors.txt‎

Lines changed: 4 additions & 4 deletions
Original file line numberDiff line numberDiff line change
@@ -1,7 +1,7 @@
11
tests/cases/compiler/expr.ts(87,5): error TS2367: This condition will always return 'false' since the types 'number' and 'string' have no overlap.
2-
tests/cases/compiler/expr.ts(88,5): error TS2367: This condition will always return 'false' since the types 'number' and 'boolean' have no overlap.
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tests/cases/compiler/expr.ts(88,5): error TS2367: This condition will always return 'false' since the types 'number' and 'false' have no overlap.
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tests/cases/compiler/expr.ts(94,5): error TS2367: This condition will always return 'false' since the types 'string' and 'number' have no overlap.
4-
tests/cases/compiler/expr.ts(95,5): error TS2367: This condition will always return 'false' since the types 'string' and 'boolean' have no overlap.
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tests/cases/compiler/expr.ts(95,5): error TS2367: This condition will always return 'false' since the types 'string' and 'false' have no overlap.
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tests/cases/compiler/expr.ts(98,5): error TS2367: This condition will always return 'false' since the types 'string' and 'E' have no overlap.
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tests/cases/compiler/expr.ts(115,5): error TS2367: This condition will always return 'false' since the types 'E' and 'string' have no overlap.
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tests/cases/compiler/expr.ts(116,5): error TS2367: This condition will always return 'false' since the types 'E' and 'false' have no overlap.
@@ -161,7 +161,7 @@ tests/cases/compiler/expr.ts(242,7): error TS2363: The right-hand side of an ari
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!!! error TS2367: This condition will always return 'false' since the types 'number' and 'string' have no overlap.
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n==b;
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~~~~
164-
!!! error TS2367: This condition will always return 'false' since the types 'number' and 'boolean' have no overlap.
164+
!!! error TS2367: This condition will always return 'false' since the types 'number' and 'false' have no overlap.
165165
n==i;
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n==n;
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n==e;
@@ -172,7 +172,7 @@ tests/cases/compiler/expr.ts(242,7): error TS2363: The right-hand side of an ari
172172
!!! error TS2367: This condition will always return 'false' since the types 'string' and 'number' have no overlap.
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s==b;
174174
~~~~
175-
!!! error TS2367: This condition will always return 'false' since the types 'string' and 'boolean' have no overlap.
175+
!!! error TS2367: This condition will always return 'false' since the types 'string' and 'false' have no overlap.
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s==i;
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s==s;
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s==e;

‎tests/baselines/reference/for-inStatementsArrayErrors.errors.txt‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,6 @@
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tests/cases/conformance/statements/for-inStatements/for-inStatementsArrayErrors.ts(4,16): error TS7015: Element implicitly has an 'any' type because index expression is not of type 'number'.
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tests/cases/conformance/statements/for-inStatements/for-inStatementsArrayErrors.ts(5,16): error TS2362: The left-hand side of an arithmetic operation must be of type 'any', 'number', 'bigint' or an enum type.
3-
tests/cases/conformance/statements/for-inStatements/for-inStatementsArrayErrors.ts(6,9): error TS2367: This condition will always return 'false' since the types 'string' and 'number' have no overlap.
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tests/cases/conformance/statements/for-inStatements/for-inStatementsArrayErrors.ts(6,9): error TS2367: This condition will always return 'false' since the types 'string' and '1' have no overlap.
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tests/cases/conformance/statements/for-inStatements/for-inStatementsArrayErrors.ts(8,16): error TS2339: Property 'unknownProperty' does not exist on type 'string'.
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tests/cases/conformance/statements/for-inStatements/for-inStatementsArrayErrors.ts(12,10): error TS2403: Subsequent variable declarations must have the same type. Variable 'i' must be of type 'number', but here has type 'string'.
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tests/cases/conformance/statements/for-inStatements/for-inStatementsArrayErrors.ts(16,10): error TS2403: Subsequent variable declarations must have the same type. Variable 'j' must be of type 'any', but here has type 'string'.
@@ -18,7 +18,7 @@ tests/cases/conformance/statements/for-inStatements/for-inStatementsArrayErrors.
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!!! error TS2362: The left-hand side of an arithmetic operation must be of type 'any', 'number', 'bigint' or an enum type.
1919
if (x === 1) {
2020
~~~~~~~
21-
!!! error TS2367: This condition will always return 'false' since the types 'string' and 'number' have no overlap.
21+
!!! error TS2367: This condition will always return 'false' since the types 'string' and '1' have no overlap.
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}
2323
let a3 = x.unknownProperty;
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~~~~~~~~~~~~~~~

‎tests/baselines/reference/stringLiteralsAssertionsInEqualityComparisons02.errors.txt‎

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@@ -1,5 +1,5 @@
11
tests/cases/conformance/types/literal/stringLiteralsAssertionsInEqualityComparisons02.ts(3,9): error TS2367: This condition will always return 'false' since the types '"foo"' and '"baz"' have no overlap.
2-
tests/cases/conformance/types/literal/stringLiteralsAssertionsInEqualityComparisons02.ts(5,9): error TS2367: This condition will always return 'false' since the types 'string' and 'number' have no overlap.
2+
tests/cases/conformance/types/literal/stringLiteralsAssertionsInEqualityComparisons02.ts(5,9): error TS2367: This condition will always return 'false' since the types '"foo"' and 'number' have no overlap.
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tests/cases/conformance/types/literal/stringLiteralsAssertionsInEqualityComparisons02.ts(5,19): error TS2352: Conversion of type 'string' to type 'number' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
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@@ -12,7 +12,7 @@ tests/cases/conformance/types/literal/stringLiteralsAssertionsInEqualityComparis
1212
var b = "foo" !== ("bar" as "foo");
1313
var c = "foo" == (<number>"bar");
1414
~~~~~~~~~~~~~~~~~~~~~~~~
15-
!!! error TS2367: This condition will always return 'false' since the types 'string' and 'number' have no overlap.
15+
!!! error TS2367: This condition will always return 'false' since the types '"foo"' and 'number' have no overlap.
1616
~~~~~~~~~~~~~
1717
!!! error TS2352: Conversion of type 'string' to type 'number' may be a mistake because neither type sufficiently overlaps with the other. If this was intentional, convert the expression to 'unknown' first.
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var d = "foo" === ("bar" as EnhancedString);

‎tests/baselines/reference/stringLiteralsWithEqualityChecks03.errors.txt‎

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@@ -1,8 +1,12 @@
11
tests/cases/conformance/types/literal/stringLiteralsWithEqualityChecks03.ts(16,5): error TS2367: This condition will always return 'false' since the types '"foo"' and '"bar"' have no overlap.
2+
tests/cases/conformance/types/literal/stringLiteralsWithEqualityChecks03.ts(19,5): error TS2367: This condition will always return 'false' since the types 'Refrigerator | "foo"' and '"bar"' have no overlap.
3+
tests/cases/conformance/types/literal/stringLiteralsWithEqualityChecks03.ts(20,5): error TS2367: This condition will always return 'false' since the types '"bar"' and 'Refrigerator | "foo"' have no overlap.
24
tests/cases/conformance/types/literal/stringLiteralsWithEqualityChecks03.ts(25,5): error TS2367: This condition will always return 'true' since the types '"foo"' and '"bar"' have no overlap.
5+
tests/cases/conformance/types/literal/stringLiteralsWithEqualityChecks03.ts(28,5): error TS2367: This condition will always return 'true' since the types 'Refrigerator | "foo"' and '"bar"' have no overlap.
6+
tests/cases/conformance/types/literal/stringLiteralsWithEqualityChecks03.ts(29,5): error TS2367: This condition will always return 'true' since the types '"bar"' and 'Refrigerator | "foo"' have no overlap.
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==== tests/cases/conformance/types/literal/stringLiteralsWithEqualityChecks03.ts (2 errors) ====
9+
==== tests/cases/conformance/types/literal/stringLiteralsWithEqualityChecks03.ts (6 errors) ====
610
interface Runnable {
711
isRunning: boolean;
812
}
@@ -24,7 +28,11 @@ tests/cases/conformance/types/literal/stringLiteralsWithEqualityChecks03.ts(25,5
2428
b = "bar" === x;
2529
b = x === "bar";
2630
b = y === "bar";
31+
~~~~~~~~~~~
32+
!!! error TS2367: This condition will always return 'false' since the types 'Refrigerator | "foo"' and '"bar"' have no overlap.
2733
b = "bar" === y;
34+
~~~~~~~~~~~
35+
!!! error TS2367: This condition will always return 'false' since the types '"bar"' and 'Refrigerator | "foo"' have no overlap.
2836

2937
b = x !== y;
3038
b = "foo" !== y
@@ -35,5 +43,9 @@ tests/cases/conformance/types/literal/stringLiteralsWithEqualityChecks03.ts(25,5
3543
b = "bar" !== x;
3644
b = x !== "bar";
3745
b = y !== "bar";
46+
~~~~~~~~~~~
47+
!!! error TS2367: This condition will always return 'true' since the types 'Refrigerator | "foo"' and '"bar"' have no overlap.
3848
b = "bar" !== y;
49+
~~~~~~~~~~~
50+
!!! error TS2367: This condition will always return 'true' since the types '"bar"' and 'Refrigerator | "foo"' have no overlap.
3951

‎tests/baselines/reference/stringLiteralsWithEqualityChecks04.errors.txt‎

Lines changed: 13 additions & 1 deletion
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@@ -1,8 +1,12 @@
11
tests/cases/conformance/types/literal/stringLiteralsWithEqualityChecks04.ts(16,5): error TS2367: This condition will always return 'false' since the types '"foo"' and '"bar"' have no overlap.
2+
tests/cases/conformance/types/literal/stringLiteralsWithEqualityChecks04.ts(19,5): error TS2367: This condition will always return 'false' since the types 'Refrigerator | "foo"' and '"bar"' have no overlap.
3+
tests/cases/conformance/types/literal/stringLiteralsWithEqualityChecks04.ts(20,5): error TS2367: This condition will always return 'false' since the types '"bar"' and 'Refrigerator | "foo"' have no overlap.
24
tests/cases/conformance/types/literal/stringLiteralsWithEqualityChecks04.ts(25,5): error TS2367: This condition will always return 'true' since the types '"foo"' and '"bar"' have no overlap.
5+
tests/cases/conformance/types/literal/stringLiteralsWithEqualityChecks04.ts(28,5): error TS2367: This condition will always return 'true' since the types 'Refrigerator | "foo"' and '"bar"' have no overlap.
6+
tests/cases/conformance/types/literal/stringLiteralsWithEqualityChecks04.ts(29,5): error TS2367: This condition will always return 'true' since the types '"bar"' and 'Refrigerator | "foo"' have no overlap.
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5-
==== tests/cases/conformance/types/literal/stringLiteralsWithEqualityChecks04.ts (2 errors) ====
9+
==== tests/cases/conformance/types/literal/stringLiteralsWithEqualityChecks04.ts (6 errors) ====
610
interface Runnable {
711
isRunning: boolean;
812
}
@@ -24,7 +28,11 @@ tests/cases/conformance/types/literal/stringLiteralsWithEqualityChecks04.ts(25,5
2428
b = "bar" == x;
2529
b = x == "bar";
2630
b = y == "bar";
31+
~~~~~~~~~~
32+
!!! error TS2367: This condition will always return 'false' since the types 'Refrigerator | "foo"' and '"bar"' have no overlap.
2733
b = "bar" == y;
34+
~~~~~~~~~~
35+
!!! error TS2367: This condition will always return 'false' since the types '"bar"' and 'Refrigerator | "foo"' have no overlap.
2836

2937
b = x != y;
3038
b = "foo" != y
@@ -35,5 +43,9 @@ tests/cases/conformance/types/literal/stringLiteralsWithEqualityChecks04.ts(25,5
3543
b = "bar" != x;
3644
b = x != "bar";
3745
b = y != "bar";
46+
~~~~~~~~~~
47+
!!! error TS2367: This condition will always return 'true' since the types 'Refrigerator | "foo"' and '"bar"' have no overlap.
3848
b = "bar" != y;
49+
~~~~~~~~~~
50+
!!! error TS2367: This condition will always return 'true' since the types '"bar"' and 'Refrigerator | "foo"' have no overlap.
3951

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