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Fixed an issue in boolean comparison narrowing when the reference is an optional chain #56504

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merged 3 commits into from
Nov 22, 2023
Merged

Fixed an issue in boolean comparison narrowing when the reference is an optional chain #56504

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2be581e
Fixed an issue in boolean comparison narrowing when the reference is …
Andarist Nov 22, 2023
b549581
add an extra test case
Andarist Nov 22, 2023
c2b785e
add another extra test case
Andarist Nov 22, 2023
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4 changes: 2 additions & 2 deletions src/compiler/checker.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -27929,10 +27929,10 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
if (isMatchingConstructorReference(right)) {
return narrowTypeByConstructor(type, operator, left, assumeTrue);
}
if (isBooleanLiteral(right)) {
if (isBooleanLiteral(right) && !isAccessExpression(left)) {
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It turns out that the original type can be reassigned based on optionalChainContainsReference. That messed up the else branch because narrowTypeByBooleanComparison was operating on the wrong type.

I've also tried keeping originalType around and pass that to narrowTypeByBooleanComparison. That fixed the reported issue~ related to the wrong type in the else branch but it broke the same type within the if block. This happened because originally the intention was for that reassigned type to be returned through the return at the bottom of this function but I changed it to return originalType through narrowTypeByBooleanComparison.

So all in all, this seems like the simplest fix and reflects the intention the best. The motivation behind the original change was to improve non-access expression narrowing. Access expressions are already handled by discrimination-based narrowing etc.

Even though it worked previously (as far as I know) for non-optional chain access expressions, this helps them avoid some redundant work too.

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This seems fine as a quick fix for now, though I suspect that we could try and do better later.

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Then again, not sure what "better" even means; an expression like (options?.a === false || options.b is not the same as (!options?.a || options.b) so realistically I don't think there's any extra info gained here.

return narrowTypeByBooleanComparison(type, left, right, operator, assumeTrue);
}
if (isBooleanLiteral(left)) {
if (isBooleanLiteral(left) && !isAccessExpression(right)) {
return narrowTypeByBooleanComparison(type, right, left, operator, assumeTrue);
}
break;
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48 changes: 48 additions & 0 deletions tests/baselines/reference/controlFlowOptionalChain3.symbols
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@@ -0,0 +1,48 @@
//// [tests/cases/conformance/controlFlow/controlFlowOptionalChain3.ts] ////

=== controlFlowOptionalChain3.ts ===
// https://github.com/microsoft/TypeScript/issues/56482

interface Foo {
>Foo : Symbol(Foo, Decl(controlFlowOptionalChain3.ts, 0, 0))

bar: boolean;
>bar : Symbol(Foo.bar, Decl(controlFlowOptionalChain3.ts, 2, 15))
}

function test1(foo: Foo | undefined) {
>test1 : Symbol(test1, Decl(controlFlowOptionalChain3.ts, 4, 1))
>foo : Symbol(foo, Decl(controlFlowOptionalChain3.ts, 6, 15))
>Foo : Symbol(Foo, Decl(controlFlowOptionalChain3.ts, 0, 0))

if (foo?.bar === false) {
>foo?.bar : Symbol(Foo.bar, Decl(controlFlowOptionalChain3.ts, 2, 15))
>foo : Symbol(foo, Decl(controlFlowOptionalChain3.ts, 6, 15))
>bar : Symbol(Foo.bar, Decl(controlFlowOptionalChain3.ts, 2, 15))

foo;
>foo : Symbol(foo, Decl(controlFlowOptionalChain3.ts, 6, 15))
}
foo;
>foo : Symbol(foo, Decl(controlFlowOptionalChain3.ts, 6, 15))
}

function test2(foo: Foo | undefined) {
>test2 : Symbol(test2, Decl(controlFlowOptionalChain3.ts, 11, 1))
>foo : Symbol(foo, Decl(controlFlowOptionalChain3.ts, 13, 15))
>Foo : Symbol(Foo, Decl(controlFlowOptionalChain3.ts, 0, 0))

if (foo?.bar === false) {
>foo?.bar : Symbol(Foo.bar, Decl(controlFlowOptionalChain3.ts, 2, 15))
>foo : Symbol(foo, Decl(controlFlowOptionalChain3.ts, 13, 15))
>bar : Symbol(Foo.bar, Decl(controlFlowOptionalChain3.ts, 2, 15))

foo;
>foo : Symbol(foo, Decl(controlFlowOptionalChain3.ts, 13, 15))

} else {
foo;
>foo : Symbol(foo, Decl(controlFlowOptionalChain3.ts, 13, 15))
}
}

48 changes: 48 additions & 0 deletions tests/baselines/reference/controlFlowOptionalChain3.types
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Original file line number Diff line number Diff line change
@@ -0,0 +1,48 @@
//// [tests/cases/conformance/controlFlow/controlFlowOptionalChain3.ts] ////

=== controlFlowOptionalChain3.ts ===
// https://github.com/microsoft/TypeScript/issues/56482

interface Foo {
bar: boolean;
>bar : boolean
}

function test1(foo: Foo | undefined) {
>test1 : (foo: Foo | undefined) => void
>foo : Foo | undefined

if (foo?.bar === false) {
>foo?.bar === false : boolean
>foo?.bar : boolean | undefined
>foo : Foo | undefined
>bar : boolean | undefined
>false : false

foo;
>foo : Foo
}
foo;
>foo : Foo | undefined
}

function test2(foo: Foo | undefined) {
>test2 : (foo: Foo | undefined) => void
>foo : Foo | undefined

if (foo?.bar === false) {
>foo?.bar === false : boolean
>foo?.bar : boolean | undefined
>foo : Foo | undefined
>bar : boolean | undefined
>false : false

foo;
>foo : Foo

} else {
foo;
>foo : Foo | undefined
}
}

23 changes: 23 additions & 0 deletions tests/cases/conformance/controlFlow/controlFlowOptionalChain3.ts
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Original file line number Diff line number Diff line change
@@ -0,0 +1,23 @@
// @strict: true
// @noEmit: true

// https://github.com/microsoft/TypeScript/issues/56482

interface Foo {
bar: boolean;
}

function test1(foo: Foo | undefined) {
if (foo?.bar === false) {
foo;
}
foo;
}

function test2(foo: Foo | undefined) {
if (foo?.bar === false) {
foo;
} else {
foo;
}
}
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