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Add support for Flow def-site variance syntax

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This syntax allows you to specify whether a type variable can appear in
a covariant or contravariant position, and is super useful for, say,
Promise.

Right now this is hacked in jankily, but in the next major release we
should stop using Identifier nodes for type parameters.
This commit is contained in:
Sam Goldman 2016-02-29 17:20:55 -08:00
parent 6adbe96bf1
commit b85d6c7e4a
3 changed files with 353 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
src/plugins/flow.js
View File

@ -624,9 +624,23 @@ pp.flowParseTypeAnnotation = function () {
};
pp.flowParseTypeAnnotatableIdentifier = function (requireTypeAnnotation, canBeOptionalParam) {
let variance;
if (this.match(tt.plusMin)) {
if (this.state.value === "+") {
variance = "plus";
} else if (this.state.value === "-") {
variance = "minus";
}
this.eat(tt.plusMin);
}
let ident = this.parseIdentifier();
let isOptionalParam = false;
if (variance) {
ident.variance = variance;
}
if (canBeOptionalParam && this.eat(tt.question)) {
this.expect(tt.question);
isOptionalParam = true;

3
test/fixtures/flow/def-site-variance/1/actual.js vendored Normal file
View File

@ -0,0 +1,3 @@
class C<+T,-U> {}
function f<+T,-U>() {}
type T<+T,-U> = {}

336
test/fixtures/flow/def-site-variance/1/expected.json vendored Normal file
View File

@ -0,0 +1,336 @@
{
"type": "File",
"start": 0,
"end": 59,
"loc": {
"start": {
"line": 1,
"column": 0
},
"end": {
"line": 3,
"column": 18
}
},
"program": {
"type": "Program",
"start": 0,
"end": 59,
"loc": {
"start": {
"line": 1,
"column": 0
},
"end": {
"line": 3,
"column": 18
}
},
"sourceType": "module",
"body": [
{
"type": "ClassDeclaration",
"start": 0,
"end": 17,
"loc": {
"start": {
"line": 1,
"column": 0
},
"end": {
"line": 1,
"column": 17
}
},
"id": {
"type": "Identifier",
"start": 6,
"end": 7,
"loc": {
"start": {
"line": 1,
"column": 6
},
"end": {
"line": 1,
"column": 7
}
},
"name": "C"
},
"typeParameters": {
"type": "TypeParameterDeclaration",
"start": 7,
"end": 14,
"loc": {
"start": {
"line": 1,
"column": 7
},
"end": {
"line": 1,
"column": 14
}
},
"params": [
{
"type": "Identifier",
"start": 9,
"end": 10,
"loc": {
"start": {
"line": 1,
"column": 9
},
"end": {
"line": 1,
"column": 10
}
},
"name": "T",
"variance": "plus"
},
{
"type": "Identifier",
"start": 12,
"end": 13,
"loc": {
"start": {
"line": 1,
"column": 12
},
"end": {
"line": 1,
"column": 13
}
},
"name": "U",
"variance": "minus"
}
]
},
"superClass": null,
"body": {
"type": "ClassBody",
"start": 15,
"end": 17,
"loc": {
"start": {
"line": 1,
"column": 15
},
"end": {
"line": 1,
"column": 17
}
},
"body": []
}
},
{
"type": "FunctionDeclaration",
"start": 18,
"end": 40,
"loc": {
"start": {
"line": 2,
"column": 0
},
"end": {
"line": 2,
"column": 22
}
},
"id": {
"type": "Identifier",
"start": 27,
"end": 28,
"loc": {
"start": {
"line": 2,
"column": 9
},
"end": {
"line": 2,
"column": 10
}
},
"name": "f"
},
"generator": false,
"expression": false,
"async": false,
"typeParameters": {
"type": "TypeParameterDeclaration",
"start": 28,
"end": 35,
"loc": {
"start": {
"line": 2,
"column": 10
},
"end": {
"line": 2,
"column": 17
}
},
"params": [
{
"type": "Identifier",
"start": 30,
"end": 31,
"loc": {
"start": {
"line": 2,
"column": 12
},
"end": {
"line": 2,
"column": 13
}
},
"name": "T",
"variance": "plus"
},
{
"type": "Identifier",
"start": 33,
"end": 34,
"loc": {
"start": {
"line": 2,
"column": 15
},
"end": {
"line": 2,
"column": 16
}
},
"name": "U",
"variance": "minus"
}
]
},
"params": [],
"body": {
"type": "BlockStatement",
"start": 38,
"end": 40,
"loc": {
"start": {
"line": 2,
"column": 20
},
"end": {
"line": 2,
"column": 22
}
},
"body": [],
"directives": []
}
},
{
"type": "TypeAlias",
"start": 41,
"end": 59,
"loc": {
"start": {
"line": 3,
"column": 0
},
"end": {
"line": 3,
"column": 18
}
},
"id": {
"type": "Identifier",
"start": 46,
"end": 47,
"loc": {
"start": {
"line": 3,
"column": 5
},
"end": {
"line": 3,
"column": 6
}
},
"name": "T"
},
"typeParameters": {
"type": "TypeParameterDeclaration",
"start": 47,
"end": 54,
"loc": {
"start": {
"line": 3,
"column": 6
},
"end": {
"line": 3,
"column": 13
}
},
"params": [
{
"type": "Identifier",
"start": 49,
"end": 50,
"loc": {
"start": {
"line": 3,
"column": 8
},
"end": {
"line": 3,
"column": 9
}
},
"name": "T",
"variance": "plus"
},
{
"type": "Identifier",
"start": 52,
"end": 53,
"loc": {
"start": {
"line": 3,
"column": 11
},
"end": {
"line": 3,
"column": 12
}
},
"name": "U",
"variance": "minus"
}
]
},
"right": {
"type": "ObjectTypeAnnotation",
"start": 57,
"end": 59,
"loc": {
"start": {
"line": 3,
"column": 16
},
"end": {
"line": 3,
"column": 18
}
},
"callProperties": [],
"properties": [],
"indexers": []
}
}
],
"directives": []
}
}