[flow][parser] add support for const type parameter

Summary: Adds support for parsing a `const` modifier in type parameters: ``` function foo<const T>(x: T): void {} ``` Typing won't be supported for now; any instance of `const` type param is an unsupported-syntax error. `const` won't be a valid name for a type parameter anymore, so the following will now be parsing errors: ``` function foo<const>(): void {}; type T<const> = {}; class C<const> {}; ``` Changelog: [internal] Reviewed By: SamChou19815 Differential Revision: D66669559 fbshipit-source-id: 17e33fb421f4e626c66c0db679b7816305c23bd5
facebook · Dec 4, 2024 · f0cfd43 · f0cfd43
1 parent 638aa1c
commit f0cfd43
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Showing 31 changed files with 971 additions and 10 deletions.
diff --git a/packages/flow-parser/test/custom_ast_types.js b/packages/flow-parser/test/custom_ast_types.js
@@ -359,11 +359,14 @@ function custom_ast_types(fork) {
     .bases('FlowType')
     .build('argument')
     .field('argument', def('FlowType'));
-  def('TypeParameter').field('usesExtendsBound', or(undefined, Boolean));
+  def('TypeParameter')
+    .field('usesExtendsBound', or(undefined, Boolean))
+    .field('const', or(def('ConstModifier'), null), defaults['null']);
   def('Variance').field(
     'kind',
     or('plus', 'minus', 'readonly', 'in', 'out', 'in-out'),
   );
+  def('ConstModifier').bases('Node');
   def('AsExpression')
     .bases('Expression')
     .build('expression', 'typeAnnotation')

diff --git a/src/analysis/scope_builder.ml b/src/analysis/scope_builder.ml
@@ -630,7 +630,7 @@ module Make (L : Loc_sig.S) (Api : Scope_api_sig.S with module L = L) :
         in
         let rec loop tps =
           match tps with
-          | (loc, { name; bound; bound_kind = _; variance; default }) :: next ->
+          | (loc, { name; bound; bound_kind = _; variance; default; const = _ }) :: next ->
             hoist_op (fun () -> ignore @@ this#type_annotation_hint bound);
             ignore @@ this#variance_opt variance;
             hoist_op (fun () -> ignore @@ Base.Option.map ~f:this#type_ default);

diff --git a/src/common/ty/ty_serializer.ml b/src/common/ty/ty_serializer.ml
@@ -156,6 +156,7 @@ let type_ options =
             bound_kind = T.TypeParam.Extends;
             variance = None;
             default = None;
+            const = None;
           }
       in
       just (T.Infer { T.Infer.tparam; comments = None })
@@ -491,6 +492,7 @@ let type_ options =
         bound_kind = T.TypeParam.Colon;
         variance = variance_ tp.tp_polarity;
         default;
+        const = None;
       }
     )
   and type_arguments ts =

diff --git a/src/parser/estree_translator.ml b/src/parser/estree_translator.ml
@@ -2187,6 +2187,7 @@ with type t = Impl.t = struct
             bound_kind;
             variance = tp_var;
             default;
+            const;
           }
         ) =
       node
@@ -2201,6 +2202,9 @@ with type t = Impl.t = struct
            ("variance", option variance tp_var);
            ("default", option _type default);
          ]
+        @ (match const with
+          | Some (loc, comments) -> [("const", node ?comments "ConstModifier" loc [])]
+          | None -> [])
         @
         match bound_kind with
         | Type.TypeParam.Colon -> []

diff --git a/src/parser/flow_ast.ml b/src/parser/flow_ast.ml
@@ -618,6 +618,10 @@ and Type : sig
       | Extends
     [@@deriving show]
 
+    module ConstModifier : sig
+      type 'M t = 'M * ('M, unit) Syntax.t option [@@deriving show]
+    end
+
     type ('M, 'T) t = 'M * ('M, 'T) t'
 
     and ('M, 'T) t' = {
@@ -626,6 +630,7 @@ and Type : sig
       bound_kind: bound_kind;
       variance: 'M Variance.t option;
       default: ('M, 'T) Type.t option;
+      const: 'M ConstModifier.t option;
     }
     [@@deriving show]
   end

diff --git a/src/parser/flow_ast_mapper.ml b/src/parser/flow_ast_mapper.ml
@@ -1547,6 +1547,14 @@ class ['loc] mapper =
 
     method variance_opt (opt : 'loc Ast.Variance.t option) = map_opt this#variance opt
 
+    method tparam_const_modifier (c : 'loc Ast.Type.TypeParam.ConstModifier.t) =
+      let (loc, comments) = c in
+      let comments' = this#syntax_opt comments in
+      if comments == comments' then
+        c
+      else
+        (loc, comments')
+
     method type_args (targs : ('loc, 'loc) Ast.Type.TypeArgs.t) =
       let open Ast.Type.TypeArgs in
       let (loc, { arguments; comments }) = targs in
@@ -1569,15 +1577,31 @@ class ['loc] mapper =
 
     method type_param (tparam : ('loc, 'loc) Ast.Type.TypeParam.t) =
       let open Ast.Type.TypeParam in
-      let (loc, { name; bound; bound_kind; variance; default }) = tparam in
+      let (loc, { name; bound; bound_kind; variance; default; const }) = tparam in
       let bound' = this#type_annotation_hint bound in
       let variance' = this#variance_opt variance in
       let default' = map_opt this#type_ default in
+      let const' = map_opt this#tparam_const_modifier const in
       let name' = this#binding_type_identifier name in
-      if name' == name && bound' == bound && variance' == variance && default' == default then
+      if
+        name' == name
+        && bound' == bound
+        && variance' == variance
+        && default' == default
+        && const' == const
+      then
         tparam
       else
-        (loc, { name = name'; bound = bound'; bound_kind; variance = variance'; default = default' })
+        ( loc,
+          {
+            name = name';
+            bound = bound';
+            bound_kind;
+            variance = variance';
+            default = default';
+            const = const';
+          }
+        )
 
     method generic_type _loc (gt : ('loc, 'loc) Ast.Type.Generic.t) =
       let open Ast.Type.Generic in

diff --git a/src/parser/flow_lexer.ml b/src/parser/flow_lexer.ml
@@ -1785,6 +1785,7 @@ let type_token env lexbuf =
     | "bigint" -> Token (env, T_BIGINT_TYPE)
     | "bool" -> Token (env, T_BOOLEAN_TYPE BOOL)
     | "boolean" -> Token (env, T_BOOLEAN_TYPE BOOLEAN)
+    | "const" -> Token (env, T_CONST)
     | "empty" -> Token (env, T_EMPTY_TYPE)
     | "extends" -> Token (env, T_EXTENDS)
     | "false" -> Token (env, T_FALSE)

diff --git a/src/parser/parser_env.ml b/src/parser/parser_env.ml
@@ -661,6 +661,7 @@ let is_reserved_type str_val =
   | "bigint"
   | "bool"
   | "boolean"
+  | "const"
   | "empty"
   | "extends"
   | "false"
@@ -691,6 +692,7 @@ let token_is_reserved_type t =
   | T_ANY_TYPE
   | T_BIGINT_TYPE
   | T_BOOLEAN_TYPE _
+  | T_CONST
   | T_EMPTY_TYPE
   | T_EXTENDS
   | T_FALSE

diff --git a/src/parser/test/flow/types/mapped_types/invalid_const_tparam.js b/src/parser/test/flow/types/mapped_types/invalid_const_tparam.js
@@ -0,0 +1 @@
+let x: {[const key in keyof O]?: T};
diff --git a/src/parser/test/flow/types/mapped_types/invalid_const_tparam.tree.json b/src/parser/test/flow/types/mapped_types/invalid_const_tparam.tree.json
@@ -0,0 +1,193 @@
+{
+  "errors":[
+    {
+      "loc":{"source":null,"start":{"line":1,"column":9},"end":{"line":1,"column":14}},
+      "message":"Unexpected token `const`, expected a type"
+    },
+    {
+      "loc":{"source":null,"start":{"line":1,"column":9},"end":{"line":1,"column":14}},
+      "message":"Unexpected token `const`, expected the token `]`"
+    },
+    {
+      "loc":{"source":null,"start":{"line":1,"column":15},"end":{"line":1,"column":18}},
+      "message":"Unexpected identifier, expected the token `:`"
+    },
+    {
+      "loc":{"source":null,"start":{"line":1,"column":22},"end":{"line":1,"column":27}},
+      "message":"Unexpected token `keyof`, expected the token `,`"
+    },
+    {
+      "loc":{"source":null,"start":{"line":1,"column":28},"end":{"line":1,"column":29}},
+      "message":"Unexpected identifier, expected the token `:`"
+    },
+    {
+      "loc":{"source":null,"start":{"line":1,"column":28},"end":{"line":1,"column":29}},
+      "message":"Unexpected identifier, expected the token `,`"
+    },
+    {
+      "loc":{"source":null,"start":{"line":1,"column":29},"end":{"line":1,"column":30}},
+      "message":"Unexpected token `]`, expected the token `:`"
+    },
+    {
+      "loc":{"source":null,"start":{"line":1,"column":29},"end":{"line":1,"column":30}},
+      "message":"Unexpected token `]`, expected the token `,`"
+    },
+    {
+      "loc":{"source":null,"start":{"line":1,"column":29},"end":{"line":1,"column":30}},
+      "message":"Unexpected token `]`, expected an identifier"
+    }
+  ],
+  "type":"Program",
+  "loc":{"source":null,"start":{"line":1,"column":0},"end":{"line":1,"column":36}},
+  "range":[0,36],
+  "body":[
+    {
+      "type":"VariableDeclaration",
+      "loc":{"source":null,"start":{"line":1,"column":0},"end":{"line":1,"column":36}},
+      "range":[0,36],
+      "declarations":[
+        {
+          "type":"VariableDeclarator",
+          "loc":{"source":null,"start":{"line":1,"column":4},"end":{"line":1,"column":35}},
+          "range":[4,35],
+          "id":{
+            "type":"Identifier",
+            "loc":{"source":null,"start":{"line":1,"column":4},"end":{"line":1,"column":35}},
+            "range":[4,35],
+            "name":"x",
+            "typeAnnotation":{
+              "type":"TypeAnnotation",
+              "loc":{"source":null,"start":{"line":1,"column":5},"end":{"line":1,"column":35}},
+              "range":[5,35],
+              "typeAnnotation":{
+                "type":"ObjectTypeAnnotation",
+                "loc":{"source":null,"start":{"line":1,"column":7},"end":{"line":1,"column":35}},
+                "range":[7,35],
+                "inexact":false,
+                "exact":false,
+                "properties":[
+                  {
+                    "type":"ObjectTypeProperty",
+                    "loc":{"source":null,"start":{"line":1,"column":22},"end":{"line":1,"column":27}},
+                    "range":[22,27],
+                    "key":{
+                      "type":"Identifier",
+                      "loc":{"source":null,"start":{"line":1,"column":22},"end":{"line":1,"column":27}},
+                      "range":[22,27],
+                      "name":"keyof",
+                      "typeAnnotation":null,
+                      "optional":false
+                    },
+                    "value":{
+                      "type":"AnyTypeAnnotation",
+                      "loc":{"source":null,"start":{"line":1,"column":22},"end":{"line":1,"column":27}},
+                      "range":[22,27]
+                    },
+                    "method":false,
+                    "optional":false,
+                    "static":false,
+                    "proto":false,
+                    "variance":null,
+                    "kind":"init"
+                  },
+                  {
+                    "type":"ObjectTypeProperty",
+                    "loc":{"source":null,"start":{"line":1,"column":28},"end":{"line":1,"column":29}},
+                    "range":[28,29],
+                    "key":{
+                      "type":"Identifier",
+                      "loc":{"source":null,"start":{"line":1,"column":28},"end":{"line":1,"column":29}},
+                      "range":[28,29],
+                      "name":"O",
+                      "typeAnnotation":null,
+                      "optional":false
+                    },
+                    "value":{
+                      "type":"AnyTypeAnnotation",
+                      "loc":{"source":null,"start":{"line":1,"column":28},"end":{"line":1,"column":29}},
+                      "range":[28,29]
+                    },
+                    "method":false,
+                    "optional":false,
+                    "static":false,
+                    "proto":false,
+                    "variance":null,
+                    "kind":"init"
+                  },
+                  {
+                    "type":"ObjectTypeProperty",
+                    "loc":{"source":null,"start":{"line":1,"column":29},"end":{"line":1,"column":34}},
+                    "range":[29,34],
+                    "key":{
+                      "type":"Identifier",
+                      "loc":{"source":null,"start":{"line":1,"column":29},"end":{"line":1,"column":30}},
+                      "range":[29,30],
+                      "name":"",
+                      "typeAnnotation":null,
+                      "optional":false
+                    },
+                    "value":{
+                      "type":"GenericTypeAnnotation",
+                      "loc":{"source":null,"start":{"line":1,"column":33},"end":{"line":1,"column":34}},
+                      "range":[33,34],
+                      "id":{
+                        "type":"Identifier",
+                        "loc":{"source":null,"start":{"line":1,"column":33},"end":{"line":1,"column":34}},
+                        "range":[33,34],
+                        "name":"T",
+                        "typeAnnotation":null,
+                        "optional":false
+                      },
+                      "typeParameters":null
+                    },
+                    "method":false,
+                    "optional":true,
+                    "static":false,
+                    "proto":false,
+                    "variance":null,
+                    "kind":"init"
+                  }
+                ],
+                "indexers":[
+                  {
+                    "type":"ObjectTypeIndexer",
+                    "loc":{"source":null,"start":{"line":1,"column":8},"end":{"line":1,"column":21}},
+                    "range":[8,21],
+                    "id":null,
+                    "key":{
+                      "type":"AnyTypeAnnotation",
+                      "loc":{"source":null,"start":{"line":1,"column":9},"end":{"line":1,"column":14}},
+                      "range":[9,14]
+                    },
+                    "value":{
+                      "type":"GenericTypeAnnotation",
+                      "loc":{"source":null,"start":{"line":1,"column":19},"end":{"line":1,"column":21}},
+                      "range":[19,21],
+                      "id":{
+                        "type":"Identifier",
+                        "loc":{"source":null,"start":{"line":1,"column":19},"end":{"line":1,"column":21}},
+                        "range":[19,21],
+                        "name":"in",
+                        "typeAnnotation":null,
+                        "optional":false
+                      },
+                      "typeParameters":null
+                    },
+                    "static":false,
+                    "variance":null
+                  }
+                ],
+                "callProperties":[],
+                "internalSlots":[]
+              }
+            },
+            "optional":false
+          },
+          "init":null
+        }
+      ],
+      "kind":"let"
+    }
+  ],
+  "comments":[]
+}
diff --git a/src/parser/test/flow/types/type_params/function_const_params.js b/src/parser/test/flow/types/type_params/function_const_params.js
@@ -0,0 +1,6 @@
+function f1<const X>(): void {}
+function f2<const X, Y>(): void {}
+function f3<X, const Y>(): void {}
+function f4<const Y = T>(): void {}
+function f5<const Y : T>(): void {}
+function f6 < /* comment 1 */ const /* comment 2 */ Y /* comment 3 */ : /* comment 4 */ T /* comment 5 */ >(): void {}
diff --git a/src/parser/test/flow/types/type_params/function_const_params.options.json b/src/parser/test/flow/types/type_params/function_const_params.options.json
@@ -0,0 +1,3 @@
+{
+  "intern_comments": true
+}