(ts) Raise syntax error for abstract methods with a body (#12687)

Co-authored-by: Nicolò Ribaudo <nicolo.ribaudo@gmail.com>

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

@@ -60,6 +60,8 @@ type ParsingContext =
   | "TypeParametersOrArguments";
 
 const TSErrors = Object.freeze({
+  AbstractMethodHasImplementation:
+    "Method '%0' cannot have an implementation because it is marked abstract.",
   ClassMethodHasDeclare: "Class methods cannot have the 'declare' modifier",
   ClassMethodHasReadonly: "Class methods cannot have the 'readonly' modifier",
   ConstructorHasTypeParameters:
@@ -2933,4 +2935,24 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         this.unexpected(null, tt._class);
       }
     }
+
+    parseMethod(...args: any[]) {
+      const method = super.parseMethod(...args);
+      if (method.abstract) {
+        const hasBody = this.hasPlugin("estree")
+          ? !!method.value.body
+          : !!method.body;
+        if (hasBody) {
+          const { key } = method;
+          this.raise(
+            method.start,
+            TSErrors.AbstractMethodHasImplementation,
+            key.type === "Identifier"
+              ? key.name
+              : `[${this.input.slice(key.start, key.end)}]`,
+          );
+        }
+      }
+      return method;
+    }
   };

packages/babel-parser/test/fixtures/typescript/class/abstract-method-with-body-computed/input.ts

@@ -0,0 +1,3 @@
+abstract class Foo {
+  abstract [foo()]() {}
+}

packages/babel-parser/test/fixtures/typescript/class/abstract-method-with-body-computed/output.json

@@ -0,0 +1,61 @@
+{
+  "type": "File",
+  "start":0,"end":46,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+  "errors": [
+    "SyntaxError: Method '[foo()]' cannot have an implementation because it is marked abstract. (2:2)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":46,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start":0,"end":46,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+        "abstract": true,
+        "id": {
+          "type": "Identifier",
+          "start":15,"end":18,"loc":{"start":{"line":1,"column":15},"end":{"line":1,"column":18},"identifierName":"Foo"},
+          "name": "Foo"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start":19,"end":46,"loc":{"start":{"line":1,"column":19},"end":{"line":3,"column":1}},
+          "body": [
+            {
+              "type": "ClassMethod",
+              "start":23,"end":44,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":23}},
+              "abstract": true,
+              "static": false,
+              "computed": true,
+              "key": {
+                "type": "CallExpression",
+                "start":33,"end":38,"loc":{"start":{"line":2,"column":12},"end":{"line":2,"column":17}},
+                "callee": {
+                  "type": "Identifier",
+                  "start":33,"end":36,"loc":{"start":{"line":2,"column":12},"end":{"line":2,"column":15},"identifierName":"foo"},
+                  "name": "foo"
+                },
+                "arguments": []
+              },
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start":42,"end":44,"loc":{"start":{"line":2,"column":21},"end":{"line":2,"column":23}},
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/typescript/class/abstract-method-with-body/input.ts

@@ -0,0 +1,3 @@
+abstract class Foo {
+  abstract method() {}
+}

packages/babel-parser/test/fixtures/typescript/class/abstract-method-with-body/output.json

@@ -0,0 +1,56 @@
+{
+  "type": "File",
+  "start":0,"end":45,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+  "errors": [
+    "SyntaxError: Method 'method' cannot have an implementation because it is marked abstract. (2:2)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":45,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start":0,"end":45,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+        "abstract": true,
+        "id": {
+          "type": "Identifier",
+          "start":15,"end":18,"loc":{"start":{"line":1,"column":15},"end":{"line":1,"column":18},"identifierName":"Foo"},
+          "name": "Foo"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start":19,"end":45,"loc":{"start":{"line":1,"column":19},"end":{"line":3,"column":1}},
+          "body": [
+            {
+              "type": "ClassMethod",
+              "start":23,"end":43,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":22}},
+              "abstract": true,
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":32,"end":38,"loc":{"start":{"line":2,"column":11},"end":{"line":2,"column":17},"identifierName":"method"},
+                "name": "method"
+              },
+              "computed": false,
+              "kind": "method",
+              "id": null,
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start":41,"end":43,"loc":{"start":{"line":2,"column":20},"end":{"line":2,"column":22}},
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/typescript/class/generator-method-with-modifiers/output.json

@@ -2,7 +2,8 @@
   "type": "File",
   "start":0,"end":139,"loc":{"start":{"line":1,"column":0},"end":{"line":9,"column":1}},
   "errors": [
-    "SyntaxError: Abstract methods can only appear within an abstract class. (5:2)"
+    "SyntaxError: Abstract methods can only appear within an abstract class. (5:2)",
+    "SyntaxError: Method 'd' cannot have an implementation because it is marked abstract. (5:2)"
   ],
   "program": {
     "type": "Program",