Improve syntax error for class fields in ambient context (#12108)

* Improve error messages for ambient context class fields

* Modify switching state.isDeclareContext for class fields with declare

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

@@ -68,7 +68,7 @@ const TSErrors = Object.freeze({
   ConstructorHasTypeParameters:
     "Type parameters cannot appear on a constructor declaration.",
   DeclareClassFieldHasInitializer:
-    "'declare' class fields cannot have an initializer",
+    "Initializers are not allowed in ambient contexts.",
   DeclareFunctionHasImplementation:
     "An implementation cannot be declared in ambient contexts.",
   DuplicateModifier: "Duplicate modifier: '%0'",
@@ -1478,10 +1478,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         kind = "let";
       }
 
-      const oldIsDeclareContext = this.state.isDeclareContext;
+      return this.tsInDeclareContext(() => {
-      this.state.isDeclareContext = true;
-
-      try {
         switch (starttype) {
           case tt._function:
             nany.declare = true;
@@ -1519,9 +1516,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
             }
           }
         }
-      } finally {
+      });
-        this.state.isDeclareContext = oldIsDeclareContext;
-      }
     }
 
     // Note: this won't be called unless the keyword is allowed in `shouldParseExportDeclaration`.
@@ -2081,7 +2076,19 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       if (accessibility) member.accessibility = accessibility;
       this.tsParseModifiers(member, ["declare"]);
 
-      super.parseClassMember(classBody, member, state, constructorAllowsSuper);
+      const callParseClassMember = () => {
+        super.parseClassMember(
+          classBody,
+          member,
+          state,
+          constructorAllowsSuper,
+        );
+      };
+      if (member.declare) {
+        this.tsInDeclareContext(callParseClassMember);
+      } else {
+        callParseClassMember();
+      }
     }
 
     parseClassMemberWithIsStatic(
@@ -2294,7 +2301,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
     parseClassProperty(node: N.ClassProperty): N.ClassProperty {
       this.parseClassPropertyAnnotation(node);
 
-      if (node.declare && this.match(tt.eq)) {
+      if (this.state.isDeclareContext && this.match(tt.eq)) {
         this.raise(this.state.start, TSErrors.DeclareClassFieldHasInitializer);
       }
 
@@ -2781,4 +2788,14 @@ export default (superClass: Class<Parser>): Class<Parser> =>
 
       return param;
     }
+
+    tsInDeclareContext<T>(cb: () => T): T {
+      const oldIsDeclareContext = this.state.isDeclareContext;
+      this.state.isDeclareContext = true;
+      try {
+        return cb();
+      } finally {
+        this.state.isDeclareContext = oldIsDeclareContext;
+      }
+    }
   };

packages/babel-parser/test/fixtures/typescript/class/declare-field-initializer/output.json

@@ -2,7 +2,7 @@
   "type": "File",
   "start":0,"end":43,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
   "errors": [
-    "SyntaxError: 'declare' class fields cannot have an initializer (2:22)"
+    "SyntaxError: Initializers are not allowed in ambient contexts. (2:22)"
   ],
   "program": {
     "type": "Program",

packages/babel-parser/test/fixtures/typescript/class/declare-initializer/input.ts

@@ -0,0 +1,3 @@
+declare class C {
+  field = "field";
+}

packages/babel-parser/test/fixtures/typescript/class/declare-initializer/output.json

@@ -0,0 +1,53 @@
+{
+  "type": "File",
+  "start":0,"end":38,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+  "errors": [
+    "SyntaxError: Initializers are not allowed in ambient contexts. (2:8)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":38,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ClassDeclaration",
+        "start":0,"end":38,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+        "declare": true,
+        "id": {
+          "type": "Identifier",
+          "start":14,"end":15,"loc":{"start":{"line":1,"column":14},"end":{"line":1,"column":15},"identifierName":"C"},
+          "name": "C"
+        },
+        "superClass": null,
+        "body": {
+          "type": "ClassBody",
+          "start":16,"end":38,"loc":{"start":{"line":1,"column":16},"end":{"line":3,"column":1}},
+          "body": [
+            {
+              "type": "ClassProperty",
+              "start":20,"end":36,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":18}},
+              "static": false,
+              "key": {
+                "type": "Identifier",
+                "start":20,"end":25,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":7},"identifierName":"field"},
+                "name": "field"
+              },
+              "computed": false,
+              "value": {
+                "type": "StringLiteral",
+                "start":28,"end":35,"loc":{"start":{"line":2,"column":10},"end":{"line":2,"column":17}},
+                "extra": {
+                  "rawValue": "field",
+                  "raw": "\"field\""
+                },
+                "value": "field"
+              }
+            }
+          ]
+        }
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/typescript/declare/module-class/input.ts

@@ -0,0 +1,5 @@
+declare module m {
+  class C {
+    field = "field";
+  }
+}

packages/babel-parser/test/fixtures/typescript/declare/module-class/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": ["typescript", "classProperties"]
+}

packages/babel-parser/test/fixtures/typescript/declare/module-class/output.json

@@ -0,0 +1,68 @@
+{
+  "type": "File",
+  "start":0,"end":57,"loc":{"start":{"line":1,"column":0},"end":{"line":5,"column":1}},
+  "errors": [
+    "SyntaxError: Initializers are not allowed in ambient contexts. (3:10)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":57,"loc":{"start":{"line":1,"column":0},"end":{"line":5,"column":1}},
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "TSModuleDeclaration",
+        "start":0,"end":57,"loc":{"start":{"line":1,"column":0},"end":{"line":5,"column":1}},
+        "id": {
+          "type": "Identifier",
+          "start":15,"end":16,"loc":{"start":{"line":1,"column":15},"end":{"line":1,"column":16},"identifierName":"m"},
+          "name": "m"
+        },
+        "body": {
+          "type": "TSModuleBlock",
+          "start":17,"end":57,"loc":{"start":{"line":1,"column":17},"end":{"line":5,"column":1}},
+          "body": [
+            {
+              "type": "ClassDeclaration",
+              "start":21,"end":55,"loc":{"start":{"line":2,"column":2},"end":{"line":4,"column":3}},
+              "id": {
+                "type": "Identifier",
+                "start":27,"end":28,"loc":{"start":{"line":2,"column":8},"end":{"line":2,"column":9},"identifierName":"C"},
+                "name": "C"
+              },
+              "superClass": null,
+              "body": {
+                "type": "ClassBody",
+                "start":29,"end":55,"loc":{"start":{"line":2,"column":10},"end":{"line":4,"column":3}},
+                "body": [
+                  {
+                    "type": "ClassProperty",
+                    "start":35,"end":51,"loc":{"start":{"line":3,"column":4},"end":{"line":3,"column":20}},
+                    "static": false,
+                    "key": {
+                      "type": "Identifier",
+                      "start":35,"end":40,"loc":{"start":{"line":3,"column":4},"end":{"line":3,"column":9},"identifierName":"field"},
+                      "name": "field"
+                    },
+                    "computed": false,
+                    "value": {
+                      "type": "StringLiteral",
+                      "start":43,"end":50,"loc":{"start":{"line":3,"column":12},"end":{"line":3,"column":19}},
+                      "extra": {
+                        "rawValue": "field",
+                        "raw": "\"field\""
+                      },
+                      "value": "field"
+                    }
+                  }
+                ]
+              }
+            }
+          ]
+        },
+        "declare": true
+      }
+    ],
+    "directives": []
+  }
+}

packages/babel-parser/test/fixtures/typescript/declare/namespace-class/input.ts

@@ -0,0 +1,6 @@
+declare namespace m {
+  class C {
+    field = "field";
+  }
+}
+  

packages/babel-parser/test/fixtures/typescript/declare/namespace-class/options.json

@@ -0,0 +1,3 @@
+{
+  "plugins": ["typescript", "classProperties"]
+}

packages/babel-parser/test/fixtures/typescript/declare/namespace-class/output.json

@@ -0,0 +1,68 @@
+{
+  "type": "File",
+  "start":0,"end":60,"loc":{"start":{"line":1,"column":0},"end":{"line":5,"column":1}},
+  "errors": [
+    "SyntaxError: Initializers are not allowed in ambient contexts. (3:10)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":60,"loc":{"start":{"line":1,"column":0},"end":{"line":5,"column":1}},
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "TSModuleDeclaration",
+        "start":0,"end":60,"loc":{"start":{"line":1,"column":0},"end":{"line":5,"column":1}},
+        "id": {
+          "type": "Identifier",
+          "start":18,"end":19,"loc":{"start":{"line":1,"column":18},"end":{"line":1,"column":19},"identifierName":"m"},
+          "name": "m"
+        },
+        "body": {
+          "type": "TSModuleBlock",
+          "start":20,"end":60,"loc":{"start":{"line":1,"column":20},"end":{"line":5,"column":1}},
+          "body": [
+            {
+              "type": "ClassDeclaration",
+              "start":24,"end":58,"loc":{"start":{"line":2,"column":2},"end":{"line":4,"column":3}},
+              "id": {
+                "type": "Identifier",
+                "start":30,"end":31,"loc":{"start":{"line":2,"column":8},"end":{"line":2,"column":9},"identifierName":"C"},
+                "name": "C"
+              },
+              "superClass": null,
+              "body": {
+                "type": "ClassBody",
+                "start":32,"end":58,"loc":{"start":{"line":2,"column":10},"end":{"line":4,"column":3}},
+                "body": [
+                  {
+                    "type": "ClassProperty",
+                    "start":38,"end":54,"loc":{"start":{"line":3,"column":4},"end":{"line":3,"column":20}},
+                    "static": false,
+                    "key": {
+                      "type": "Identifier",
+                      "start":38,"end":43,"loc":{"start":{"line":3,"column":4},"end":{"line":3,"column":9},"identifierName":"field"},
+                      "name": "field"
+                    },
+                    "computed": false,
+                    "value": {
+                      "type": "StringLiteral",
+                      "start":46,"end":53,"loc":{"start":{"line":3,"column":12},"end":{"line":3,"column":19}},
+                      "extra": {
+                        "rawValue": "field",
+                        "raw": "\"field\""
+                      },
+                      "value": "field"
+                    }
+                  }
+                ]
+              }
+            }
+          ]
+        },
+        "declare": true
+      }
+    ],
+    "directives": []
+  }
+}