Address review comment

packages/babel-parser/src/parser/expression.js

@@ -2101,6 +2101,8 @@ export default class ExpressionParser extends LValParser {
     node: N.BodilessFunctionOrMethodBase,
     type: string,
     isMethod?: boolean = false,
+    // eslint-disable-next-line no-unused-vars -- this is used in /plugins/typescript
+    isDeclare?: boolean = false,
   ): void {
     // $FlowIgnore (node is not bodiless if we get here)
     this.parseFunctionBody(node, false, isMethod);

packages/babel-parser/src/parser/statement.js

@@ -144,14 +144,22 @@ export default class StatementParser extends ExpressionParser {
   // https://tc39.es/ecma262/#prod-Statement
   // ImportDeclaration and ExportDeclaration are also handled here so we can throw recoverable errors
   // when they are not at the top level
-  parseStatement(context: ?string, topLevel?: boolean): N.Statement {
+  parseStatement(
+    context: ?string,
+    topLevel?: boolean,
+    isDeclare?: boolean = false,
+  ): N.Statement {
     if (this.match(tt.at)) {
       this.parseDecorators(true);
     }
-    return this.parseStatementContent(context, topLevel);
+    return this.parseStatementContent(context, topLevel, isDeclare);
   }
 
-  parseStatementContent(context: ?string, topLevel: ?boolean): N.Statement {
+  parseStatementContent(
+    context: ?string,
+    topLevel: ?boolean,
+    isDeclare?: boolean = false,
+  ): N.Statement {
     let starttype = this.state.type;
     const node = this.startNode();
     let kind;
@@ -185,7 +193,7 @@ export default class StatementParser extends ExpressionParser {
             this.raise(this.state.start, Errors.SloppyFunction);
           }
         }
-        return this.parseFunctionStatement(node, false, !context);
+        return this.parseFunctionStatement(node, false, !context, isDeclare);
 
       case tt._class:
         if (context) this.unexpected();
@@ -541,12 +549,14 @@ export default class StatementParser extends ExpressionParser {
     node: N.FunctionDeclaration,
     isAsync?: boolean,
     declarationPosition?: boolean,
+    isDeclare?: boolean = false,
   ): N.FunctionDeclaration {
     this.next();
     return this.parseFunction(
       node,
       FUNC_STATEMENT | (declarationPosition ? 0 : FUNC_HANGING_STATEMENT),
       isAsync,
+      isDeclare,
     );
   }
 
@@ -856,6 +866,7 @@ export default class StatementParser extends ExpressionParser {
     topLevel: boolean,
     end: TokenType,
     afterBlockParse?: (hasStrictModeDirective: boolean) => void,
+    isDeclare?: boolean = false,
   ): void {
     const octalPositions = [];
     const oldStrict = this.state.strict;
@@ -868,7 +879,7 @@ export default class StatementParser extends ExpressionParser {
         octalPositions.push(...this.state.octalPositions);
       }
 
-      const stmt = this.parseStatement(null, topLevel);
+      const stmt = this.parseStatement(null, topLevel, isDeclare);
 
       if (directives && !parsedNonDirective && this.isValidDirective(stmt)) {
         const directive = this.stmtToDirective(stmt);
@@ -1054,6 +1065,7 @@ export default class StatementParser extends ExpressionParser {
     node: T,
     statement?: number = FUNC_NO_FLAGS,
     isAsync?: boolean = false,
+    isDeclare?: boolean = false,
   ): T {
     const isStatement = statement & FUNC_STATEMENT;
     const isHangingStatement = statement & FUNC_HANGING_STATEMENT;
@@ -1093,6 +1105,8 @@ export default class StatementParser extends ExpressionParser {
       this.parseFunctionBodyAndFinish(
         node,
         isStatement ? "FunctionDeclaration" : "FunctionExpression",
+        /* method */ false,
+        isDeclare,
       );
     });
 

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

@@ -1314,7 +1314,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       return this.finishNode(node, "TSEnumDeclaration");
     }
 
-    tsParseModuleBlock(): N.TsModuleBlock {
+    tsParseModuleBlock(isDeclare?: boolean = false): N.TsModuleBlock {
       const node: N.TsModuleBlock = this.startNode();
       this.scope.enter(SCOPE_OTHER);
 
@@ -1325,6 +1325,8 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         /* directives */ undefined,
         /* topLevel */ true,
         /* end */ tt.braceR,
+        /* afterBlockParse */ undefined,
+        /* declare */ isDeclare,
       );
       this.scope.exit();
       return this.finishNode(node, "TSModuleBlock");
@@ -1333,6 +1335,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
     tsParseModuleOrNamespaceDeclaration(
       node: N.TsModuleDeclaration,
       nested?: boolean = false,
+      isDeclare?: boolean = false,
     ): N.TsModuleDeclaration {
       node.id = this.parseIdentifier();
 
@@ -1352,7 +1355,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       } else {
         this.scope.enter(SCOPE_TS_MODULE);
         this.prodParam.enter(PARAM);
-        node.body = this.tsParseModuleBlock();
+        node.body = this.tsParseModuleBlock(isDeclare);
         this.prodParam.exit();
         this.scope.exit();
       }
@@ -1474,6 +1477,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
             nany,
             /* async */ false,
             /* declarationPosition */ true,
+            /* declare */ true,
           );
         case tt._class:
           // While this is also set by tsParseExpressionStatement, we need to set it
@@ -1500,7 +1504,12 @@ export default (superClass: Class<Parser>): Class<Parser> =>
           if (value === "global") {
             return this.tsParseAmbientExternalModuleDeclaration(nany);
           } else {
-            return this.tsParseDeclaration(nany, value, /* next */ true);
+            return this.tsParseDeclaration(
+              nany,
+              value,
+              /* next */ true,
+              /* declare */ true,
+            );
           }
         }
       }
@@ -1551,6 +1560,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       node: any,
       value: string,
       next: boolean,
+      isDeclare?: boolean = false,
     ): ?N.Declaration {
       switch (value) {
         case "abstract":
@@ -1597,7 +1607,11 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         case "namespace":
           if (this.tsCheckLineTerminatorAndMatch(tt.name, next)) {
             if (next) this.next();
-            return this.tsParseModuleOrNamespaceDeclaration(node);
+            return this.tsParseModuleOrNamespaceDeclaration(
+              node,
+              /* nested */ false,
+              isDeclare,
+            );
           }
           break;
 
@@ -1745,6 +1759,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       node: N.BodilessFunctionOrMethodBase,
       type: string,
       isMethod?: boolean = false,
+      isDeclare?: boolean = false,
     ): void {
       if (this.match(tt.colon)) {
         node.returnType = this.tsParseTypeOrTypePredicateAnnotation(tt.colon);
@@ -1760,14 +1775,15 @@ export default (superClass: Class<Parser>): Class<Parser> =>
         this.finishNode(node, bodilessType);
         return;
       }
-      if (
-        bodilessType === "TSDeclareFunction" &&
-        // $FlowIgnore
-        node.declare
-      ) {
+      if (bodilessType === "TSDeclareFunction" && isDeclare) {
         this.raise(node.start, TSErrors.DeclareFunctionHasImplementation);
-        this.finishNode(node, bodilessType);
-        return;
+        if (
+          // $FlowIgnore
+          node.declare
+        ) {
+          this.finishNode(node, bodilessType);
+          return;
+        }
       }
 
       super.parseFunctionBodyAndFinish(node, type, isMethod);
@@ -2028,7 +2044,11 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       return super.parseExportDefaultExpression();
     }
 
-    parseStatementContent(context: ?string, topLevel: ?boolean): N.Statement {
+    parseStatementContent(
+      context: ?string,
+      topLevel: ?boolean,
+      isDeclare?: boolean = false,
+    ): N.Statement {
       if (this.state.type === tt._const) {
         const ahead = this.lookahead();
         if (ahead.type === tt.name && ahead.value === "enum") {
@@ -2038,7 +2058,7 @@ export default (superClass: Class<Parser>): Class<Parser> =>
           return this.tsParseEnumDeclaration(node, /* isConst */ true);
         }
       }
-      return super.parseStatementContent(context, topLevel);
+      return super.parseStatementContent(context, topLevel, isDeclare);
     }
 
     parseAccessModifier(): ?N.Accessibility {

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": []
+  }
+}