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[parser] Add parser support for _ in constructors and calls
Summary: This diff adds support for parsing `_`, which will be used to specify that a type parameter should be implicitly instantiated. We add a new ast node to the Expression module, `TypeParameterInstantiation`. This is reminiscent of `Type`'s `ParameterInstantiation`, except that instead of a list of `Type.t`s, it contains a list of `Implicit of Loc.t | Explicit of Type.t`. When parsing `New` and `Call` type arguments, we parse `_` as an `Implicit` and all other types `t` as `Explicit t`. Creating the new ast node comes with a number of benefits: 1. External consumers of our AST currently consume `ParameterInstantiation` as it was originally designed: for type arguments to polymorphic types. Creating a new AST node makes sure we don't need to update all of those external consumers. 2. This new AST node allows OCaml to enforce the invariant that `_` can only appear in `Call` and `New`. 3. Related to 2., this more faithfully models the structure of our AST. `Call` and `New` have type arguments, but the fact that we used the same representation as we did for `Type` was just because they happened to have the same internal representation. These types are types we come across when parsing an expression, not a type annotation. We also now say that `_` is a reserved keyword when it's found in type positions, so it cannot be used unless it means implicit instantiation. We need to update babel to consider "_" to be a reserved identifier in type positions and to parse `_` as an `ImplicitInstantiationAnnotation`. Reviewed By: samwgoldman Differential Revision: D10105957 fbshipit-source-id: 3003b0cadbb1f9163a07bae1957710e9fbdeccdd
1 parent d2b32ea commit fb23b93

28 files changed

Lines changed: 887 additions & 27 deletions

‎src/parser/estree_translator.ml‎

Lines changed: 14 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -450,7 +450,7 @@ end with type t = Impl.t) = struct
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| loc, New _new -> New.(
451451
node "NewExpression" loc [
452452
"callee", expression _new.callee;
453-
"typeArguments", option type_parameter_instantiation _new.targs;
453+
"typeArguments", option type_parameter_instantiation_with_implicit _new.targs;
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"arguments", array_of_list expression_or_spread _new.arguments;
455455
]
456456
)
@@ -1030,6 +1030,13 @@ end with type t = Impl.t) = struct
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| Exists -> exists_type loc
10311031
)
10321032

1033+
and implicit loc = generic_type (loc,
1034+
{Type.Generic.id = Type.Generic.Identifier.Unqualified (loc, "_"); targs = None})
1035+
1036+
and explicit_or_implicit_targ x = match x with
1037+
| Expression.TypeParameterInstantiation.Explicit t -> _type t
1038+
| Expression.TypeParameterInstantiation.Implicit loc -> implicit loc
1039+
10331040
and any_type loc = node "AnyTypeAnnotation" loc []
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and mixed_type loc = node "MixedTypeAnnotation" loc []
@@ -1273,6 +1280,11 @@ end with type t = Impl.t) = struct
12731280
"params", array_of_list _type targs;
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]
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1283+
and type_parameter_instantiation_with_implicit (loc, targs) =
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node "TypeParameterInstantiation" loc [
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"params", array_of_list explicit_or_implicit_targ targs;
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]
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12761288
and jsx_element (loc, (element: (Loc.t, Loc.t) JSX.element)) = JSX.(
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node "JSXElement" loc [
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"openingElement", jsx_opening element.openingElement;
@@ -1458,7 +1470,7 @@ end with type t = Impl.t) = struct
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and call_node_properties call = Expression.Call.([
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"callee", expression call.callee;
1461-
"typeArguments", option type_parameter_instantiation call.targs;
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"typeArguments", option type_parameter_instantiation_with_implicit call.targs;
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"arguments", array_of_list expression_or_spread call.arguments;
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])
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‎src/parser/expression_parser.ml‎

Lines changed: 31 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -572,7 +572,7 @@ module Expression
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(* Parameterized call syntax is ambiguous, so we fall back to
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standard parsing if it fails. *)
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Try.or_else env ~fallback:left (fun env ->
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let targs = Type.type_parameter_instantiation env in
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let targs = type_parameter_instantiation env in
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arguments ?targs env
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)
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| _ -> left
@@ -622,7 +622,7 @@ module Expression
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standard parsing if it fails. *)
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let error_callback _ _ = raise Try.Rollback in
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let env = env |> with_error_callback error_callback in
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Try.or_else env ~fallback:None Type.type_parameter_instantiation
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Try.or_else env ~fallback:None type_parameter_instantiation
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else
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None
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in
@@ -637,6 +637,35 @@ module Expression
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arguments;
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}))
639639

640+
and type_parameter_instantiation =
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let args env acc =
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let rec args_helper env acc =
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match Peek.token env with
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| T_EOF
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| T_GREATER_THAN -> List.rev acc
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| _ ->
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let t = match Peek.token env with
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| T_IDENTIFIER {value = "_"; _} ->
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let loc = Peek.loc env in
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Expect.identifier env "_";
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Expression.TypeParameterInstantiation.Implicit loc
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| _ -> Expression.TypeParameterInstantiation.Explicit(Type._type env)
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in
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let acc = t::acc in
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if Peek.token env <> T_GREATER_THAN
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then Expect.token env T_COMMA;
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args_helper env acc
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in args_helper env acc
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in fun env -> if Peek.token env = T_LESS_THAN then
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Some (with_loc (fun env ->
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Expect.token env T_LESS_THAN;
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let args = args env [] in
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Expect.token env T_GREATER_THAN;
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args
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) env)
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else None
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and arguments =
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let argument env =
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match Peek.token env with

‎src/parser/flow_ast.ml‎

Lines changed: 11 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -249,6 +249,7 @@ and Type : sig
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and ('M, 'T) t' = ('M, 'T) TypeParam.t list
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[@@deriving show]
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end
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252253
module ParameterInstantiation : sig
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type ('M, 'T) t = 'M * ('M, 'T) t'
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and ('M, 'T) t' = ('M, 'T) Type.t list
@@ -627,6 +628,14 @@ and Statement : sig
627628
end = Statement
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629630
and Expression : sig
631+
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module TypeParameterInstantiation : sig
633+
type ('M, 'T) t = 'M * ('M, 'T) t'
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and ('M, 'T) type_parameter_instantiation = Explicit of ('M, 'T) Type.t | Implicit of 'T
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and ('M, 'T) t' = ('M, 'T) type_parameter_instantiation list
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[@@deriving show]
637+
end
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630639
module SpreadElement : sig
631640
type ('M, 'T) t = 'M * ('M, 'T) t'
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and ('M, 'T) t' = {
@@ -838,15 +847,15 @@ and Expression : sig
838847
module New : sig
839848
type ('M, 'T) t = {
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callee: ('M, 'T) Expression.t;
841-
targs: ('M, 'T) Type.ParameterInstantiation.t option;
850+
targs: ('M, 'T) Expression.TypeParameterInstantiation.t option;
842851
arguments: ('M, 'T) expression_or_spread list;
843852
}
844853
[@@deriving show]
845854
end
846855
module Call : sig
847856
type ('M, 'T) t = {
848857
callee: ('M, 'T) Expression.t;
849-
targs: ('M, 'T) Type.ParameterInstantiation.t option;
858+
targs: ('M, 'T) Expression.TypeParameterInstantiation.t option;
850859
arguments: ('M, 'T) expression_or_spread list;
851860
}
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[@@deriving show]

‎src/parser/parser_env.ml‎

Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -440,7 +440,7 @@ let is_reserved str_val =
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let is_reserved_type str_val =
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match str_val with
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| "any" | "bool" | "boolean" | "empty" | "false" | "mixed" | "null" | "number"
443-
| "static" | "string" | "true" | "typeof" | "void" | "interface" | "extends"
443+
| "static" | "string" | "true" | "typeof" | "void" | "interface" | "extends" | "_"
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-> true
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| _ -> false
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‎src/parser/test/flow/types/annotations/underscore_is_allowed_trailing_commas.js‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,7 @@
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test<
2+
_,
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_,
4+
number,
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_,
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_,
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>();

‎src/parser/test/flow/types/annotations/underscore_is_allowed_trailing_commas.tree.json‎

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,96 @@
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{
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"type":"Program",
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"loc":{"source":null,"start":{"line":1,"column":0},"end":{"line":7,"column":4}},
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"range":[0,40],
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"body":[
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{
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"type":"ExpressionStatement",
8+
"loc":{"source":null,"start":{"line":1,"column":0},"end":{"line":7,"column":4}},
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"range":[0,40],
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"expression":{
11+
"type":"CallExpression",
12+
"loc":{"source":null,"start":{"line":1,"column":0},"end":{"line":7,"column":3}},
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"range":[0,39],
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"callee":{
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"type":"Identifier",
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"loc":{"source":null,"start":{"line":1,"column":0},"end":{"line":1,"column":4}},
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"range":[0,4],
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"name":"test",
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"typeAnnotation":null,
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"optional":false
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},
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"typeArguments":{
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"type":"TypeParameterInstantiation",
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"loc":{"source":null,"start":{"line":1,"column":4},"end":{"line":7,"column":1}},
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"range":[4,37],
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"params":[
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{
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"type":"GenericTypeAnnotation",
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"loc":{"source":null,"start":{"line":2,"column":2},"end":{"line":2,"column":3}},
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"range":[8,9],
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"id":{
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"type":"Identifier",
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"loc":{"source":null,"start":{"line":2,"column":2},"end":{"line":2,"column":3}},
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"range":[8,9],
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"name":"_",
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"typeAnnotation":null,
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"optional":false
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},
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"typeParameters":null
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},
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{
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"type":"GenericTypeAnnotation",
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"loc":{"source":null,"start":{"line":3,"column":2},"end":{"line":3,"column":3}},
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"range":[13,14],
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"id":{
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"type":"Identifier",
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"loc":{"source":null,"start":{"line":3,"column":2},"end":{"line":3,"column":3}},
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"range":[13,14],
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"name":"_",
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"typeAnnotation":null,
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"optional":false
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},
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"typeParameters":null
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},
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{
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"type":"NumberTypeAnnotation",
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"loc":{"source":null,"start":{"line":4,"column":2},"end":{"line":4,"column":8}},
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"range":[18,24]
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},
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{
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"type":"GenericTypeAnnotation",
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"loc":{"source":null,"start":{"line":5,"column":2},"end":{"line":5,"column":3}},
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"range":[28,29],
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"id":{
65+
"type":"Identifier",
66+
"loc":{"source":null,"start":{"line":5,"column":2},"end":{"line":5,"column":3}},
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"range":[28,29],
68+
"name":"_",
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"typeAnnotation":null,
70+
"optional":false
71+
},
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"typeParameters":null
73+
},
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{
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"type":"GenericTypeAnnotation",
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"loc":{"source":null,"start":{"line":6,"column":2},"end":{"line":6,"column":3}},
77+
"range":[33,34],
78+
"id":{
79+
"type":"Identifier",
80+
"loc":{"source":null,"start":{"line":6,"column":2},"end":{"line":6,"column":3}},
81+
"range":[33,34],
82+
"name":"_",
83+
"typeAnnotation":null,
84+
"optional":false
85+
},
86+
"typeParameters":null
87+
}
88+
]
89+
},
90+
"arguments":[]
91+
},
92+
"directive":null
93+
}
94+
],
95+
"comments":[]
96+
}

‎src/parser/test/flow/types/annotations/underscore_is_implicit_anywhere_in_list.js‎

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1 @@
1+
test<number, _, string, _, _, _, Foo, Bar, Baz>();

‎src/parser/test/flow/types/annotations/underscore_is_implicit_anywhere_in_list.tree.json‎

Lines changed: 143 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,143 @@
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{
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"type":"Program",
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"loc":{"source":null,"start":{"line":1,"column":0},"end":{"line":1,"column":50}},
4+
"range":[0,50],
5+
"body":[
6+
{
7+
"type":"ExpressionStatement",
8+
"loc":{"source":null,"start":{"line":1,"column":0},"end":{"line":1,"column":50}},
9+
"range":[0,50],
10+
"expression":{
11+
"type":"CallExpression",
12+
"loc":{"source":null,"start":{"line":1,"column":0},"end":{"line":1,"column":49}},
13+
"range":[0,49],
14+
"callee":{
15+
"type":"Identifier",
16+
"loc":{"source":null,"start":{"line":1,"column":0},"end":{"line":1,"column":4}},
17+
"range":[0,4],
18+
"name":"test",
19+
"typeAnnotation":null,
20+
"optional":false
21+
},
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"typeArguments":{
23+
"type":"TypeParameterInstantiation",
24+
"loc":{"source":null,"start":{"line":1,"column":4},"end":{"line":1,"column":47}},
25+
"range":[4,47],
26+
"params":[
27+
{
28+
"type":"NumberTypeAnnotation",
29+
"loc":{"source":null,"start":{"line":1,"column":5},"end":{"line":1,"column":11}},
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"range":[5,11]
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},
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{
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"type":"GenericTypeAnnotation",
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"loc":{"source":null,"start":{"line":1,"column":13},"end":{"line":1,"column":14}},
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"range":[13,14],
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"id":{
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"type":"Identifier",
38+
"loc":{"source":null,"start":{"line":1,"column":13},"end":{"line":1,"column":14}},
39+
"range":[13,14],
40+
"name":"_",
41+
"typeAnnotation":null,
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"optional":false
43+
},
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"typeParameters":null
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},
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{
47+
"type":"StringTypeAnnotation",
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"loc":{"source":null,"start":{"line":1,"column":16},"end":{"line":1,"column":22}},
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"range":[16,22]
50+
},
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{
52+
"type":"GenericTypeAnnotation",
53+
"loc":{"source":null,"start":{"line":1,"column":24},"end":{"line":1,"column":25}},
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"range":[24,25],
55+
"id":{
56+
"type":"Identifier",
57+
"loc":{"source":null,"start":{"line":1,"column":24},"end":{"line":1,"column":25}},
58+
"range":[24,25],
59+
"name":"_",
60+
"typeAnnotation":null,
61+
"optional":false
62+
},
63+
"typeParameters":null
64+
},
65+
{
66+
"type":"GenericTypeAnnotation",
67+
"loc":{"source":null,"start":{"line":1,"column":27},"end":{"line":1,"column":28}},
68+
"range":[27,28],
69+
"id":{
70+
"type":"Identifier",
71+
"loc":{"source":null,"start":{"line":1,"column":27},"end":{"line":1,"column":28}},
72+
"range":[27,28],
73+
"name":"_",
74+
"typeAnnotation":null,
75+
"optional":false
76+
},
77+
"typeParameters":null
78+
},
79+
{
80+
"type":"GenericTypeAnnotation",
81+
"loc":{"source":null,"start":{"line":1,"column":30},"end":{"line":1,"column":31}},
82+
"range":[30,31],
83+
"id":{
84+
"type":"Identifier",
85+
"loc":{"source":null,"start":{"line":1,"column":30},"end":{"line":1,"column":31}},
86+
"range":[30,31],
87+
"name":"_",
88+
"typeAnnotation":null,
89+
"optional":false
90+
},
91+
"typeParameters":null
92+
},
93+
{
94+
"type":"GenericTypeAnnotation",
95+
"loc":{"source":null,"start":{"line":1,"column":33},"end":{"line":1,"column":36}},
96+
"range":[33,36],
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"id":{
98+
"type":"Identifier",
99+
"loc":{"source":null,"start":{"line":1,"column":33},"end":{"line":1,"column":36}},
100+
"range":[33,36],
101+
"name":"Foo",
102+
"typeAnnotation":null,
103+
"optional":false
104+
},
105+
"typeParameters":null
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},
107+
{
108+
"type":"GenericTypeAnnotation",
109+
"loc":{"source":null,"start":{"line":1,"column":38},"end":{"line":1,"column":41}},
110+
"range":[38,41],
111+
"id":{
112+
"type":"Identifier",
113+
"loc":{"source":null,"start":{"line":1,"column":38},"end":{"line":1,"column":41}},
114+
"range":[38,41],
115+
"name":"Bar",
116+
"typeAnnotation":null,
117+
"optional":false
118+
},
119+
"typeParameters":null
120+
},
121+
{
122+
"type":"GenericTypeAnnotation",
123+
"loc":{"source":null,"start":{"line":1,"column":43},"end":{"line":1,"column":46}},
124+
"range":[43,46],
125+
"id":{
126+
"type":"Identifier",
127+
"loc":{"source":null,"start":{"line":1,"column":43},"end":{"line":1,"column":46}},
128+
"range":[43,46],
129+
"name":"Baz",
130+
"typeAnnotation":null,
131+
"optional":false
132+
},
133+
"typeParameters":null
134+
}
135+
]
136+
},
137+
"arguments":[]
138+
},
139+
"directive":null
140+
}
141+
],
142+
"comments":[]
143+
}

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