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GeezerVison is showing github.com — Adding support for tuple types (e.g. [number, string]) by ahejlsberg · Pull Request #428 · microsoft/TypeScript

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Anders Hejlsberg (ahejlsberg) commented Aug 11, 2014

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This commit adds support for typle types. A tuple type is written as a comma separated sequence of types enclosed in square brackets:

[T0, T1, ... , Tn]

A tuple type corresponds to an object type that extends Array<T>, where T is the best common type of the tuple element types, with a sequence of numerically named members:

{
    0: T0;
    1: T1;
    ...
    n: Tn;
}

When an array literal is contextually typed by a tuple type, each of the array literal expressions are contextually typed by the corresponding tuple element type, and the result is a tuple type:

var t: [number, string] = [1, "hello"];
t = [];                 // Error
t = [1];                // Error
t = [2, "test"];        // Ok
t = ["test", 2];        // Error
t = [2, "test", true];  // Ok

When a value of a tuple type is indexed with a numeric constant, the resulting type is that of the corresponding type element. For example:

var x: [number, string] = [1, "hello"];
var x0 = x[0];  // Type number
var x1 = x[1];  // Type string
var x2 = x[2];  // Type {}

A tuple type is assignable to a compatible array type. For example:

var a1: number[];
var a2: {}[];
var t1: [number, string];
var t2: [number, number];
a1 = t1;  // Error
a1 = t2;  // Ok
a2 = t1;  // Ok
a2 = t2;  // Ok

Type inference works as expected for tuple types:

function tuple2<T0, T1>(item0: T0, item1: T1): [T0, T1] {
    return [item0, item1];
}
var t = tuple2("test", true);
var t0 = t[0];  // string
var t1 = t[1];  // boolean

Next step is to support EcmaScript 6 style destructuring of objects, arrays, and tuples.

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          Adding support for tuple types (e.g. [number, string])

5b25524

CyrusNajmabadi reviewed

Aug 11, 2014

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src/compiler/checker.ts Outdated

Cyrus Najmabadi (CyrusNajmabadi) Aug 11, 2014

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add newline after the &&

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Anders Hejlsberg (ahejlsberg) Aug 11, 2014

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Yup.

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Cyrus Najmabadi (CyrusNajmabadi) commented Aug 11, 2014

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This looks good. but i'm not sure now is the right time to be working on new features when we haven't even reached parity yet with the existing compiler. We need to get things like the TypeWriter and what not back online before we make changes that might introduce regressions that we don't have the infrastructure in place to catch.

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danquirk reviewed

Aug 11, 2014

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tests/cases/compiler/tupleTypes.ts

Dan Quirk (danquirk) Aug 11, 2014

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Would be worth breaking this up into a few different files by concept (ex tupleTypeInference, etc).

We also need a lot more coverage here. We should have tests for things like

var x = 0;
var y = 3;
var tt = tuple2(1, "a");
var r1 = tt[x];
var r2 = tt[y];

Tuples crossing module boundaries, usages in class hierarchies with array types, assignability with nested tuples and nested arrays, etc.

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          Addressing CR feedback, adding baselines.

3b1dbad

Basarat Ali Syed (basarat) commented Aug 12, 2014

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♨️ 😎

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Jason Freeman (JsonFreeman) commented Aug 12, 2014

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Looks good, although please validate this with typeWriter (not online yet) before merging into master

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DanielRosenwasser reviewed

Aug 13, 2014

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src/compiler/checker.ts

Daniel Rosenwasser (DanielRosenwasser) Aug 13, 2014

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Good ol' η-reduction.

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Basarat Ali Syed (basarat) Aug 13, 2014

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someone ate my tea

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Jason Freeman (JsonFreeman) Aug 13, 2014

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Someone eta my tea

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Daniel Rosenwasser (DanielRosenwasser) Aug 13, 2014

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👍

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Anders Hejlsberg (ahejlsberg) added 3 commits

August 13, 2014 07:15


          Addressing CR feedback.

ef52312


          Adding error message for empty tuple types.

92b3677


          Accepting new baselines.

f0b33b3

Ryan Cavanaugh (RyanCavanaugh) mentioned this pull request

Aug 15, 2014

Destructuring (ES6) #240

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Anders Hejlsberg (ahejlsberg) added 3 commits

August 16, 2014 11:11


          Merge branch 'master' into tupleTypes

0cf503f

Conflicts:
	tests/baselines/reference/typeName1.errors.txt


          Accepting new baselines after merge.

c0e802d


          Contextual typing of array literals is now based on the presence or a…

63b83e7

…bsence

of numerically named properties and doesn't directly test for tuple types.

Anders Hejlsberg (ahejlsberg) commented Aug 17, 2014

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I have revised the contextual typing logic for array literals based on the discussions we had at the design meeting. Specifically:

In an array literal contextually typed by a type T, the contextual type of an element expression at index N is the type of the property with the numeric name N in T, if one exists. Otherwise, it is the type of the numeric index signature in T, if one exists. When at least one element expression is contextually typed by a numerically named property, the resulting type of the array literal expression is a tuple type. Otherwise the resulting type is an array type.

With these rules there's nothing special about tuple types when it comes to contextual typing, and manually defined tuple-like type works just as well. For example:

interface Tuple2<T0, T1> {
    0: T0;
    1: T1;
}
var t: Tuple2<number, string> = [1, "hello"];
var x = t[0];  // number
var y = t[1];  // string

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JsonFreeman reviewed

Aug 19, 2014

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src/compiler/types.ts

Jason Freeman (JsonFreeman) Aug 19, 2014

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After you merge the changes from typeWriter (now in master), be sure to modify SyntaxKind.LastTypeNode accordingly.

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Anders Hejlsberg (ahejlsberg) added 2 commits

September 5, 2014 13:52


          Merge branch 'master' into tupleTypes

be7e0a7


          Merge branch 'master' into tupleTypes

b4cddc3

Anders Hejlsberg (ahejlsberg) added a commit that referenced this pull request

Sep 15, 2014


          Merge pull request #428 from Microsoft/tupleTypes

11b9118

Adding support for tuple types (e.g. [number, string])

Anders Hejlsberg (ahejlsberg) merged commit 11b9118 into master

Sep 15, 2014

Anders Hejlsberg (ahejlsberg) deleted the tupleTypes branch

September 15, 2014 19:58

Yui (yuit) mentioned this pull request

Oct 4, 2014

Tuple conformance #822

Merged

Kagami Sascha Rosylight (saschanaz) mentioned this pull request

Nov 1, 2014

Typed ...rest parameters with generics #1024

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