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Use constraint for default default value if possible (#28222)

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This commit is contained in:
Wesley Wigham
2018-10-30 14:55:30 -07:00
committed by GitHub
parent 4cfff8962c
commit e2436f331a
6 changed files with 70 additions and 1 deletions
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2
src/compiler/checker.ts
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@@ -7653,7 +7653,7 @@ namespace ts {
// If a type parameter does not have a default type, or if the default type
// is a forward reference, the empty object type is used.
for (let i = numTypeArguments; i < numTypeParameters; i++) {
result[i] = getDefaultTypeArgumentType(isJavaScriptImplicitAny);
result[i] = getConstraintFromTypeParameter(typeParameters![i]) || getDefaultTypeArgumentType(isJavaScriptImplicitAny);
}
for (let i = numTypeArguments; i < numTypeParameters; i++) {
const mapper = createTypeMapper(typeParameters!, result);

18
tests/baselines/reference/typeArgumentDefaultUsesConstraintOnCircularDefault.errors.txt Normal file
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@@ -0,0 +1,18 @@
tests/cases/compiler/typeArgumentDefaultUsesConstraintOnCircularDefault.ts(3,18): error TS2322: Type '{ foo: string; }' is not assignable to type 'Test<string>'.
Object literal may only specify known properties, and 'foo' does not exist in type 'Test<string>'.
tests/cases/compiler/typeArgumentDefaultUsesConstraintOnCircularDefault.ts(5,19): error TS2322: Type '{}' is not assignable to type 'string'.
==== tests/cases/compiler/typeArgumentDefaultUsesConstraintOnCircularDefault.ts (2 errors) ====
type Test<T extends string = T> = { value: T };
let zz: Test = { foo: "abc" }; // should error on comparison with Test<string>
~~~~~~~~~~
!!! error TS2322: Type '{ foo: string; }' is not assignable to type 'Test<string>'.
!!! error TS2322: Object literal may only specify known properties, and 'foo' does not exist in type 'Test<string>'.
let zzy: Test = { value: {} }; // should error
~~~~~
!!! error TS2322: Type '{}' is not assignable to type 'string'.
!!! related TS6500 tests/cases/compiler/typeArgumentDefaultUsesConstraintOnCircularDefault.ts:1:37: The expected type comes from property 'value' which is declared here on type 'Test<string>'

11
tests/baselines/reference/typeArgumentDefaultUsesConstraintOnCircularDefault.js Normal file
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@@ -0,0 +1,11 @@
//// [typeArgumentDefaultUsesConstraintOnCircularDefault.ts]
type Test<T extends string = T> = { value: T };
let zz: Test = { foo: "abc" }; // should error on comparison with Test<string>
let zzy: Test = { value: {} }; // should error
//// [typeArgumentDefaultUsesConstraintOnCircularDefault.js]
var zz = { foo: "abc" }; // should error on comparison with Test<string>
var zzy = { value: {} }; // should error

18
tests/baselines/reference/typeArgumentDefaultUsesConstraintOnCircularDefault.symbols Normal file
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@@ -0,0 +1,18 @@
=== tests/cases/compiler/typeArgumentDefaultUsesConstraintOnCircularDefault.ts ===
type Test<T extends string = T> = { value: T };
>Test : Symbol(Test, Decl(typeArgumentDefaultUsesConstraintOnCircularDefault.ts, 0, 0))
>T : Symbol(T, Decl(typeArgumentDefaultUsesConstraintOnCircularDefault.ts, 0, 10))
>T : Symbol(T, Decl(typeArgumentDefaultUsesConstraintOnCircularDefault.ts, 0, 10))
>value : Symbol(value, Decl(typeArgumentDefaultUsesConstraintOnCircularDefault.ts, 0, 35))
>T : Symbol(T, Decl(typeArgumentDefaultUsesConstraintOnCircularDefault.ts, 0, 10))
let zz: Test = { foo: "abc" }; // should error on comparison with Test<string>
>zz : Symbol(zz, Decl(typeArgumentDefaultUsesConstraintOnCircularDefault.ts, 2, 3))
>Test : Symbol(Test, Decl(typeArgumentDefaultUsesConstraintOnCircularDefault.ts, 0, 0))
>foo : Symbol(foo, Decl(typeArgumentDefaultUsesConstraintOnCircularDefault.ts, 2, 16))
let zzy: Test = { value: {} }; // should error
>zzy : Symbol(zzy, Decl(typeArgumentDefaultUsesConstraintOnCircularDefault.ts, 4, 3))
>Test : Symbol(Test, Decl(typeArgumentDefaultUsesConstraintOnCircularDefault.ts, 0, 0))
>value : Symbol(value, Decl(typeArgumentDefaultUsesConstraintOnCircularDefault.ts, 4, 17))

17
tests/baselines/reference/typeArgumentDefaultUsesConstraintOnCircularDefault.types Normal file
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@@ -0,0 +1,17 @@
=== tests/cases/compiler/typeArgumentDefaultUsesConstraintOnCircularDefault.ts ===
type Test<T extends string = T> = { value: T };
>Test : Test<T>
>value : T
let zz: Test = { foo: "abc" }; // should error on comparison with Test<string>
>zz : Test<string>
>{ foo: "abc" } : { foo: string; }
>foo : string
>"abc" : "abc"
let zzy: Test = { value: {} }; // should error
>zzy : Test<string>
>{ value: {} } : { value: {}; }
>value : {}
>{} : {}

5
tests/cases/compiler/typeArgumentDefaultUsesConstraintOnCircularDefault.ts Normal file
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@@ -0,0 +1,5 @@
type Test<T extends string = T> = { value: T };
let zz: Test = { foo: "abc" }; // should error on comparison with Test<string>
let zzy: Test = { value: {} }; // should error