Support parsing abstract interface

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

@@ -89,6 +89,8 @@ const TSErrors = Object.freeze({
     "Tuple members must all have names or all not have names.",
   NonAbstractClassHasAbstractMethod:
     "Abstract methods can only appear within an abstract class.",
+  NonClassMethodPropertyHasAbstractModifer:
+    "'abstract' modifier can only appear on a class, method, or property declaration.",
   OptionalTypeBeforeRequired:
     "A required element cannot follow an optional element.",
   PatternIsOptional:
@@ -1585,20 +1587,13 @@ export default (superClass: Class<Parser>): Class<Parser> =>
     ): ?N.Declaration {
       switch (value) {
         case "abstract":
-          if (this.tsCheckLineTerminatorAndMatch(tt._class, next)) {
-            const cls: N.ClassDeclaration = node;
-            cls.abstract = true;
-            if (next) {
-              this.next();
-              if (!this.match(tt._class)) {
-                this.unexpected(null, tt._class);
-              }
-            }
-            return this.parseClass(
-              cls,
-              /* isStatement */ true,
-              /* optionalId */ false,
-            );
+          if (
+            this.tsCheckLineTerminatorAndMatch(tt._class, next) ||
+            // for interface
+            this.tsCheckLineTerminatorAndMatch(tt.name, next)
+          ) {
+            if (next) this.next();
+            return this.tsParseAbstractDeclaration(node);
           }
           break;
 
@@ -2849,4 +2844,31 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         this.state.inAbstractClass = oldInAbstractClass;
       }
     }
+
+    tsParseAbstractDeclaration(
+      node: any,
+    ): N.ClassDeclaration | N.TsInterfaceDeclaration {
+      const isClass = this.match(tt._class);
+      if (!isClass && !this.isContextual("interface")) {
+        this.unexpected(null, tt._class);
+      }
+      node.abstract = true;
+      if (isClass) {
+        return this.parseClass(
+          (node: N.ClassDeclaration),
+          /* isStatement */ true,
+          /* optionalId */ false,
+        );
+      } else {
+        // for invalid abstract interface
+        this.raise(
+          node.start,
+          TSErrors.NonClassMethodPropertyHasAbstractModifer,
+        );
+        this.next();
+        return this.tsParseInterfaceDeclaration(
+          (node: N.TsInterfaceDeclaration),
+        );
+      }
+    }
   };

packages/babel-parser/test/fixtures/typescript/interface/abstract/input.ts

@@ -0,0 +1,3 @@
+abstract interface Foo {
+  foo: string;
+}

packages/babel-parser/test/fixtures/typescript/interface/abstract/output.json

@@ -0,0 +1,50 @@
+{
+  "type": "File",
+  "start":0,"end":41,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+  "errors": [
+    "SyntaxError: 'abstract' modifier can only appear on a class, method, or property declaration. (1:0)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":41,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "TSInterfaceDeclaration",
+        "start":0,"end":41,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+        "abstract": true,
+        "id": {
+          "type": "Identifier",
+          "start":19,"end":22,"loc":{"start":{"line":1,"column":19},"end":{"line":1,"column":22},"identifierName":"Foo"},
+          "name": "Foo"
+        },
+        "body": {
+          "type": "TSInterfaceBody",
+          "start":23,"end":41,"loc":{"start":{"line":1,"column":23},"end":{"line":3,"column":1}},
+          "body": [
+            {
+              "type": "TSPropertySignature",
+              "start":27,"end":39,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":14}},
+              "key": {
+                "type": "Identifier",
+                "start":27,"end":30,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":5},"identifierName":"foo"},
+                "name": "foo"
+              },
+              "computed": false,
+              "typeAnnotation": {
+                "type": "TSTypeAnnotation",
+                "start":30,"end":38,"loc":{"start":{"line":2,"column":5},"end":{"line":2,"column":13}},
+                "typeAnnotation": {
+                  "type": "TSStringKeyword",
+                  "start":32,"end":38,"loc":{"start":{"line":2,"column":7},"end":{"line":2,"column":13}}
+                }
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/typescript/interface/export-abstract-interface/output.json

@@ -0,0 +1,38 @@
+{
+  "type": "File",
+  "start":0,"end":32,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+  "errors": [
+    "SyntaxError: 'abstract' modifier can only appear on a class, method, or property declaration. (1:7)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":32,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ExportNamedDeclaration",
+        "start":0,"end":32,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+        "exportKind": "type",
+        "specifiers": [],
+        "source": null,
+        "declaration": {
+          "type": "TSInterfaceDeclaration",
+          "start":7,"end":32,"loc":{"start":{"line":1,"column":7},"end":{"line":3,"column":1}},
+          "abstract": true,
+          "id": {
+            "type": "Identifier",
+            "start":26,"end":27,"loc":{"start":{"line":1,"column":26},"end":{"line":1,"column":27},"identifierName":"I"},
+            "name": "I"
+          },
+          "body": {
+            "type": "TSInterfaceBody",
+            "start":28,"end":32,"loc":{"start":{"line":1,"column":28},"end":{"line":3,"column":1}},
+            "body": []
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}