Throw a syntax error for a declare function with a body (#12054)

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

@@ -69,6 +69,8 @@ const TSErrors = Object.freeze({
     "Type parameters cannot appear on a constructor declaration.",
   DeclareClassFieldHasInitializer:
     "'declare' class fields cannot have an initializer",
+  DeclareFunctionHasImplementation:
+    "An implementation cannot be declared in ambient contexts.",
   DuplicateModifier: "Duplicate modifier: '%0'",
   EmptyHeritageClauseType: "'%0' list cannot be empty.",
   IndexSignatureHasAbstract:
@@ -1469,8 +1471,13 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         kind = "let";
       }
 
+      const oldIsDeclareContext = this.state.isDeclareContext;
+      this.state.isDeclareContext = true;
+
+      try {
         switch (starttype) {
           case tt._function:
+            nany.declare = true;
             return this.parseFunctionStatement(
               nany,
               /* async */ false,
@@ -1505,6 +1512,9 @@ 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`.
@@ -1764,6 +1774,16 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         this.finishNode(node, bodilessType);
         return;
       }
+      if (bodilessType === "TSDeclareFunction" && this.state.isDeclareContext) {
+        this.raise(node.start, TSErrors.DeclareFunctionHasImplementation);
+        if (
+          // $FlowIgnore
+          node.declare
+        ) {
+          super.parseFunctionBodyAndFinish(node, bodilessType, isMethod);
+          return;
+        }
+      }
 
       super.parseFunctionBodyAndFinish(node, type, isMethod);
     }

packages/babel-parser/src/tokenizer/state.js

@@ -70,6 +70,7 @@ export default class State {
   inPropertyName: boolean = false;
   hasFlowComment: boolean = false;
   isIterator: boolean = false;
+  isDeclareContext: boolean = false;
 
   // For the smartPipelines plugin:
   topicContext: TopicContextState = {

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

@@ -0,0 +1 @@
+declare function foo() {}

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

@@ -0,0 +1,35 @@
+{
+  "type": "File",
+  "start":0,"end":25,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":25}},
+  "errors": [
+    "SyntaxError: An implementation cannot be declared in ambient contexts. (1:0)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":25,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":25}},
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "TSDeclareFunction",
+        "start":0,"end":25,"loc":{"start":{"line":1,"column":0},"end":{"line":1,"column":25}},
+        "declare": true,
+        "id": {
+          "type": "Identifier",
+          "start":17,"end":20,"loc":{"start":{"line":1,"column":17},"end":{"line":1,"column":20},"identifierName":"foo"},
+          "name": "foo"
+        },
+        "generator": false,
+        "async": false,
+        "params": [],
+        "body": {
+          "type": "BlockStatement",
+          "start":23,"end":25,"loc":{"start":{"line":1,"column":23},"end":{"line":1,"column":25}},
+          "body": [],
+          "directives": []
+        }
+      }
+    ],
+    "directives": []
+  }
+}

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

@@ -0,0 +1,3 @@
+declare module m {
+  function foo() {}
+}

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

@@ -0,0 +1,50 @@
+{
+  "type": "File",
+  "start":0,"end":40,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+  "errors": [
+    "SyntaxError: An implementation cannot be declared in ambient contexts. (2:2)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":40,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "TSModuleDeclaration",
+        "start":0,"end":40,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"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":40,"loc":{"start":{"line":1,"column":17},"end":{"line":3,"column":1}},
+          "body": [
+            {
+              "type": "FunctionDeclaration",
+              "start":21,"end":38,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":19}},
+              "id": {
+                "type": "Identifier",
+                "start":30,"end":33,"loc":{"start":{"line":2,"column":11},"end":{"line":2,"column":14},"identifierName":"foo"},
+                "name": "foo"
+              },
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start":36,"end":38,"loc":{"start":{"line":2,"column":17},"end":{"line":2,"column":19}},
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        },
+        "declare": true
+      }
+    ],
+    "directives": []
+  }
+}

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

@@ -0,0 +1,3 @@
+declare namespace n {
+  function foo() {}
+}

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

@@ -0,0 +1,50 @@
+{
+  "type": "File",
+  "start":0,"end":43,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+  "errors": [
+    "SyntaxError: An implementation cannot be declared in ambient contexts. (2:2)"
+  ],
+  "program": {
+    "type": "Program",
+    "start":0,"end":43,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+    "sourceType": "module",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "TSModuleDeclaration",
+        "start":0,"end":43,"loc":{"start":{"line":1,"column":0},"end":{"line":3,"column":1}},
+        "id": {
+          "type": "Identifier",
+          "start":18,"end":19,"loc":{"start":{"line":1,"column":18},"end":{"line":1,"column":19},"identifierName":"n"},
+          "name": "n"
+        },
+        "body": {
+          "type": "TSModuleBlock",
+          "start":20,"end":43,"loc":{"start":{"line":1,"column":20},"end":{"line":3,"column":1}},
+          "body": [
+            {
+              "type": "FunctionDeclaration",
+              "start":24,"end":41,"loc":{"start":{"line":2,"column":2},"end":{"line":2,"column":19}},
+              "id": {
+                "type": "Identifier",
+                "start":33,"end":36,"loc":{"start":{"line":2,"column":11},"end":{"line":2,"column":14},"identifierName":"foo"},
+                "name": "foo"
+              },
+              "generator": false,
+              "async": false,
+              "params": [],
+              "body": {
+                "type": "BlockStatement",
+                "start":39,"end":41,"loc":{"start":{"line":2,"column":17},"end":{"line":2,"column":19}},
+                "body": [],
+                "directives": []
+              }
+            }
+          ]
+        },
+        "declare": true
+      }
+    ],
+    "directives": []
+  }
+}