Support parsing Flow's Indexed Access Types

packages/babel-generator/src/generators/flow.ts

@@ -738,3 +738,10 @@ export function Variance(this: Printer, node: t.Variance) {
 export function VoidTypeAnnotation(this: Printer) {
   this.word("void");
 }
+
+export function IndexedAccessType(this: Printer, node: t.IndexedAccessType) {
+  this.print(node.objectType, node);
+  this.token("[");
+  this.print(node.indexType, node);
+  this.token("]");
+}

packages/babel-generator/test/fixtures/flow/indexed-access-types/input.js

@@ -0,0 +1,9 @@
+type A = Obj['a'];
+
+type B = Array<string>[number];
+
+type C = Obj['bar'][foo]['boz'];
+
+type D = (Obj['bar'])['baz'];
+
+type E = Obj['bar'][];

packages/babel-generator/test/fixtures/flow/indexed-access-types/output.js

@@ -0,0 +1,5 @@
+type A = Obj['a'];
+type B = Array<string>[number];
+type C = Obj['bar'][foo]['boz'];
+type D = Obj['bar']['baz'];
+type E = Obj['bar'][];

packages/babel-parser/src/plugins/flow/index.js

@@ -1624,10 +1624,20 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       let type = this.flowParsePrimaryType();
       while (this.match(tt.bracketL) && !this.canInsertSemicolon()) {
         const node = this.startNodeAt(startPos, startLoc);
-        node.elementType = type;
         this.expect(tt.bracketL);
-        this.expect(tt.bracketR);
-        type = this.finishNode(node, "ArrayTypeAnnotation");
+        if (this.match(tt.bracketR)) {
+          node.elementType = type;
+          this.next(); // eat `]`
+          type = this.finishNode(node, "ArrayTypeAnnotation");
+        } else {
+          node.objectType = type;
+          node.indexType = this.flowParseType();
+          this.expect(tt.bracketR);
+          type = this.finishNode<N.FlowIndexedAccessType>(
+            node,
+            "IndexedAccessType",
+          );
+        }
       }
       return type;
     }

packages/babel-parser/src/types.js

@@ -1050,6 +1050,12 @@ export type FlowInterfaceType = NodeBase & {
   body: FlowObjectTypeAnnotation,
 };
 
+export type FlowIndexedAccessType = Node & {
+  type: "IndexedAccessType",
+  objectType: FlowType,
+  indexType: FlowType,
+};
+
 // ESTree
 
 export type EstreeProperty = NodeBase & {

packages/babel-parser/test/fixtures/flow/indexed-access-types/1/input.js

@@ -0,0 +1,9 @@
+type A = Obj['a'];
+
+type B = Array<string>[number];
+
+type C = Obj['bar'][foo]['boz'];
+
+type D = (Obj['bar'])['baz'];
+
+type E = Obj['bar'][];

packages/babel-parser/test/fixtures/flow/indexed-access-types/1/output.json

@@ -0,0 +1,226 @@
+{
+  "type": "File",
+  "start":0,"end":140,"loc":{"start":{"line":1,"column":0},"end":{"line":9,"column":22}},
+  "program": {
+    "type": "Program",
+    "start":0,"end":140,"loc":{"start":{"line":1,"column":0},"end":{"line":9,"column":22}},
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "TypeAlias",
+        "start":0,"end":18,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":18}},
+        "id": {
+          "type": "Identifier",
+          "start":5,"end":6,"loc":{"start":{"line":1,"column":5},"end":{"line":1,"column":6},"identifierName":"A"},
+          "name": "A"
+        },
+        "typeParameters": null,
+        "right": {
+          "type": "IndexedAccessType",
+          "start":9,"end":17,"loc":{"start":{"line":1,"column":9},"end":{"line":1,"column":17}},
+          "objectType": {
+            "type": "GenericTypeAnnotation",
+            "start":9,"end":12,"loc":{"start":{"line":1,"column":9},"end":{"line":1,"column":12}},
+            "typeParameters": null,
+            "id": {
+              "type": "Identifier",
+              "start":9,"end":12,"loc":{"start":{"line":1,"column":9},"end":{"line":1,"column":12},"identifierName":"Obj"},
+              "name": "Obj"
+            }
+          },
+          "indexType": {
+            "type": "StringLiteralTypeAnnotation",
+            "start":13,"end":16,"loc":{"start":{"line":1,"column":13},"end":{"line":1,"column":16}},
+            "extra": {
+              "rawValue": "a",
+              "raw": "'a'"
+            },
+            "value": "a"
+          }
+        }
+      },
+      {
+        "type": "TypeAlias",
+        "start":20,"end":51,"loc":{"start":{"line":3,"column":0},"end":{"line":3,"column":31}},
+        "id": {
+          "type": "Identifier",
+          "start":25,"end":26,"loc":{"start":{"line":3,"column":5},"end":{"line":3,"column":6},"identifierName":"B"},
+          "name": "B"
+        },
+        "typeParameters": null,
+        "right": {
+          "type": "IndexedAccessType",
+          "start":29,"end":50,"loc":{"start":{"line":3,"column":9},"end":{"line":3,"column":30}},
+          "objectType": {
+            "type": "GenericTypeAnnotation",
+            "start":29,"end":42,"loc":{"start":{"line":3,"column":9},"end":{"line":3,"column":22}},
+            "typeParameters": {
+              "type": "TypeParameterInstantiation",
+              "start":34,"end":42,"loc":{"start":{"line":3,"column":14},"end":{"line":3,"column":22}},
+              "params": [
+                {
+                  "type": "StringTypeAnnotation",
+                  "start":35,"end":41,"loc":{"start":{"line":3,"column":15},"end":{"line":3,"column":21}}
+                }
+              ]
+            },
+            "id": {
+              "type": "Identifier",
+              "start":29,"end":34,"loc":{"start":{"line":3,"column":9},"end":{"line":3,"column":14},"identifierName":"Array"},
+              "name": "Array"
+            }
+          },
+          "indexType": {
+            "type": "NumberTypeAnnotation",
+            "start":43,"end":49,"loc":{"start":{"line":3,"column":23},"end":{"line":3,"column":29}}
+          }
+        }
+      },
+      {
+        "type": "TypeAlias",
+        "start":53,"end":85,"loc":{"start":{"line":5,"column":0},"end":{"line":5,"column":32}},
+        "id": {
+          "type": "Identifier",
+          "start":58,"end":59,"loc":{"start":{"line":5,"column":5},"end":{"line":5,"column":6},"identifierName":"C"},
+          "name": "C"
+        },
+        "typeParameters": null,
+        "right": {
+          "type": "IndexedAccessType",
+          "start":62,"end":84,"loc":{"start":{"line":5,"column":9},"end":{"line":5,"column":31}},
+          "objectType": {
+            "type": "IndexedAccessType",
+            "start":62,"end":77,"loc":{"start":{"line":5,"column":9},"end":{"line":5,"column":24}},
+            "objectType": {
+              "type": "IndexedAccessType",
+              "start":62,"end":72,"loc":{"start":{"line":5,"column":9},"end":{"line":5,"column":19}},
+              "objectType": {
+                "type": "GenericTypeAnnotation",
+                "start":62,"end":65,"loc":{"start":{"line":5,"column":9},"end":{"line":5,"column":12}},
+                "typeParameters": null,
+                "id": {
+                  "type": "Identifier",
+                  "start":62,"end":65,"loc":{"start":{"line":5,"column":9},"end":{"line":5,"column":12},"identifierName":"Obj"},
+                  "name": "Obj"
+                }
+              },
+              "indexType": {
+                "type": "StringLiteralTypeAnnotation",
+                "start":66,"end":71,"loc":{"start":{"line":5,"column":13},"end":{"line":5,"column":18}},
+                "extra": {
+                  "rawValue": "bar",
+                  "raw": "'bar'"
+                },
+                "value": "bar"
+              }
+            },
+            "indexType": {
+              "type": "GenericTypeAnnotation",
+              "start":73,"end":76,"loc":{"start":{"line":5,"column":20},"end":{"line":5,"column":23}},
+              "typeParameters": null,
+              "id": {
+                "type": "Identifier",
+                "start":73,"end":76,"loc":{"start":{"line":5,"column":20},"end":{"line":5,"column":23},"identifierName":"foo"},
+                "name": "foo"
+              }
+            }
+          },
+          "indexType": {
+            "type": "StringLiteralTypeAnnotation",
+            "start":78,"end":83,"loc":{"start":{"line":5,"column":25},"end":{"line":5,"column":30}},
+            "extra": {
+              "rawValue": "boz",
+              "raw": "'boz'"
+            },
+            "value": "boz"
+          }
+        }
+      },
+      {
+        "type": "TypeAlias",
+        "start":87,"end":116,"loc":{"start":{"line":7,"column":0},"end":{"line":7,"column":29}},
+        "id": {
+          "type": "Identifier",
+          "start":92,"end":93,"loc":{"start":{"line":7,"column":5},"end":{"line":7,"column":6},"identifierName":"D"},
+          "name": "D"
+        },
+        "typeParameters": null,
+        "right": {
+          "type": "IndexedAccessType",
+          "start":96,"end":115,"loc":{"start":{"line":7,"column":9},"end":{"line":7,"column":28}},
+          "objectType": {
+            "type": "IndexedAccessType",
+            "start":97,"end":107,"loc":{"start":{"line":7,"column":10},"end":{"line":7,"column":20}},
+            "objectType": {
+              "type": "GenericTypeAnnotation",
+              "start":97,"end":100,"loc":{"start":{"line":7,"column":10},"end":{"line":7,"column":13}},
+              "typeParameters": null,
+              "id": {
+                "type": "Identifier",
+                "start":97,"end":100,"loc":{"start":{"line":7,"column":10},"end":{"line":7,"column":13},"identifierName":"Obj"},
+                "name": "Obj"
+              }
+            },
+            "indexType": {
+              "type": "StringLiteralTypeAnnotation",
+              "start":101,"end":106,"loc":{"start":{"line":7,"column":14},"end":{"line":7,"column":19}},
+              "extra": {
+                "rawValue": "bar",
+                "raw": "'bar'"
+              },
+              "value": "bar"
+            }
+          },
+          "indexType": {
+            "type": "StringLiteralTypeAnnotation",
+            "start":109,"end":114,"loc":{"start":{"line":7,"column":22},"end":{"line":7,"column":27}},
+            "extra": {
+              "rawValue": "baz",
+              "raw": "'baz'"
+            },
+            "value": "baz"
+          }
+        }
+      },
+      {
+        "type": "TypeAlias",
+        "start":118,"end":140,"loc":{"start":{"line":9,"column":0},"end":{"line":9,"column":22}},
+        "id": {
+          "type": "Identifier",
+          "start":123,"end":124,"loc":{"start":{"line":9,"column":5},"end":{"line":9,"column":6},"identifierName":"E"},
+          "name": "E"
+        },
+        "typeParameters": null,
+        "right": {
+          "type": "ArrayTypeAnnotation",
+          "start":127,"end":139,"loc":{"start":{"line":9,"column":9},"end":{"line":9,"column":21}},
+          "elementType": {
+            "type": "IndexedAccessType",
+            "start":127,"end":137,"loc":{"start":{"line":9,"column":9},"end":{"line":9,"column":19}},
+            "objectType": {
+              "type": "GenericTypeAnnotation",
+              "start":127,"end":130,"loc":{"start":{"line":9,"column":9},"end":{"line":9,"column":12}},
+              "typeParameters": null,
+              "id": {
+                "type": "Identifier",
+                "start":127,"end":130,"loc":{"start":{"line":9,"column":9},"end":{"line":9,"column":12},"identifierName":"Obj"},
+                "name": "Obj"
+              }
+            },
+            "indexType": {
+              "type": "StringLiteralTypeAnnotation",
+              "start":131,"end":136,"loc":{"start":{"line":9,"column":13},"end":{"line":9,"column":18}},
+              "extra": {
+                "rawValue": "bar",
+                "raw": "'bar'"
+              },
+              "value": "bar"
+            }
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-traverse/src/path/generated/asserts.ts

@@ -257,6 +257,9 @@ export interface NodePathAssetions {
   assertImportSpecifier(
     opts?: object,
   ): asserts this is NodePath<t.ImportSpecifier>;
+  assertIndexedAccessType(
+    opts?: object,
+  ): asserts this is NodePath<t.IndexedAccessType>;
   assertInferredPredicate(
     opts?: object,
   ): asserts this is NodePath<t.InferredPredicate>;

packages/babel-traverse/src/path/generated/validators.ts

@@ -149,6 +149,7 @@ export interface NodePathValidators {
     opts?: object,
   ): this is NodePath<t.ImportNamespaceSpecifier>;
   isImportSpecifier(opts?: object): this is NodePath<t.ImportSpecifier>;
+  isIndexedAccessType(opts?: object): this is NodePath<t.IndexedAccessType>;
   isInferredPredicate(opts?: object): this is NodePath<t.InferredPredicate>;
   isInterfaceDeclaration(
     opts?: object,

packages/babel-types/src/asserts/generated/index.ts

@@ -878,6 +878,12 @@ export function assertEnumDefaultedMember(
 ): asserts node is t.EnumDefaultedMember {
   assert("EnumDefaultedMember", node, opts);
 }
+export function assertIndexedAccessType(
+  node: object | null | undefined,
+  opts?: object | null,
+): asserts node is t.IndexedAccessType {
+  assert("IndexedAccessType", node, opts);
+}
 export function assertJSXAttribute(
   node: object | null | undefined,
   opts?: object | null,

packages/babel-types/src/ast-types/generated/index.ts

@@ -151,6 +151,7 @@ export type Node =
   | ImportDefaultSpecifier
   | ImportNamespaceSpecifier
   | ImportSpecifier
+  | IndexedAccessType
   | InferredPredicate
   | InterfaceDeclaration
   | InterfaceExtends
@@ -1387,6 +1388,12 @@ export interface EnumDefaultedMember extends BaseNode {
   id: Identifier;
 }
 
+export interface IndexedAccessType extends BaseNode {
+  type: "IndexedAccessType";
+  objectType: FlowType;
+  indexType: FlowType;
+}
+
 export interface JSXAttribute extends BaseNode {
   type: "JSXAttribute";
   name: JSXIdentifier | JSXNamespacedName;

packages/babel-types/src/builders/generated/index.ts

@@ -854,6 +854,12 @@ export function enumStringMember(
 export function enumDefaultedMember(id: t.Identifier): t.EnumDefaultedMember {
   return builder("EnumDefaultedMember", ...arguments);
 }
+export function indexedAccessType(
+  objectType: t.FlowType,
+  indexType: t.FlowType,
+): t.IndexedAccessType {
+  return builder("IndexedAccessType", ...arguments);
+}
 export function jsxAttribute(
   name: t.JSXIdentifier | t.JSXNamespacedName,
   value?:

packages/babel-types/src/builders/generated/uppercase.js

@@ -153,6 +153,7 @@ export {
   enumNumberMember as EnumNumberMember,
   enumStringMember as EnumStringMember,
   enumDefaultedMember as EnumDefaultedMember,
+  indexedAccessType as IndexedAccessType,
   jsxAttribute as JSXAttribute,
   jsxClosingElement as JSXClosingElement,
   jsxElement as JSXElement,

packages/babel-types/src/definitions/flow.ts

@@ -559,3 +559,11 @@ defineType("EnumDefaultedMember", {
     id: validateType("Identifier"),
   },
 });
+
+defineType("IndexedAccessType", {
+  visitor: ["objectType", "indexType"],
+  fields: {
+    objectType: validateType("FlowType"),
+    indexType: validateType("FlowType"),
+  },
+});