fix: Types containing comments generate invalid code

packages/babel-generator/src/generators/flow.ts

@@ -11,7 +11,7 @@ export function ArrayTypeAnnotation(
   this: Printer,
   node: t.ArrayTypeAnnotation,
 ) {
-  this.print(node.elementType, node);
+  this.print(node.elementType, node, true);
   this.token("[");
   this.token("]");
 }
@@ -357,7 +357,7 @@ export function FunctionTypeParam(this: Printer, node: t.FunctionTypeParam) {
 
 export function InterfaceExtends(this: Printer, node: t.InterfaceExtends) {
   this.print(node.id, node);
-  this.print(node.typeParameters, node);
+  this.print(node.typeParameters, node, true);
 }
 
 export {
@@ -758,7 +758,7 @@ export function VoidTypeAnnotation(this: Printer) {
 }
 
 export function IndexedAccessType(this: Printer, node: t.IndexedAccessType) {
-  this.print(node.objectType, node);
+  this.print(node.objectType, node, true);
   this.token("[");
   this.print(node.indexType, node);
   this.token("]");

packages/babel-generator/src/generators/methods.ts

@@ -11,15 +11,7 @@ export function _params(
   this._parameters(node.params, node);
   this.token(")");
 
-  if (node.returnType) {
-    if (node.type === "ArrowFunctionExpression") {
-      this._noLineTerminator = true;
-      this.print(node.returnType, node);
-      this._noLineTerminator = false;
-    } else {
-      this.print(node.returnType, node);
-    }
-  }
+  this.print(node.returnType, node, node.type === "ArrowFunctionExpression");
 }
 
 export function _parameters(

packages/babel-generator/src/generators/typescript.ts

@@ -259,8 +259,8 @@ export function tsPrintFunctionOrConstructorType(
 }
 
 export function TSTypeReference(this: Printer, node: t.TSTypeReference) {
-  this.print(node.typeName, node);
-  this.print(node.typeParameters, node);
+  this.print(node.typeName, node, true);
+  this.print(node.typeParameters, node, true);
 }
 
 export function TSTypePredicate(this: Printer, node: t.TSTypePredicate) {
@@ -317,7 +317,8 @@ function tsPrintBraced(printer: Printer, members: t.Node[], node: t.Node) {
 }
 
 export function TSArrayType(this: Printer, node: t.TSArrayType) {
-  this.print(node.elementType, node);
+  this.print(node.elementType, node, true);
+
   this.token("[]");
 }
 
@@ -408,7 +409,7 @@ export function TSIndexedAccessType(
   this: Printer,
   node: t.TSIndexedAccessType,
 ) {
-  this.print(node.objectType, node);
+  this.print(node.objectType, node, true);
   this.token("[");
   this.print(node.indexType, node);
   this.token("]");

packages/babel-generator/src/printer.ts

@@ -1,7 +1,6 @@
 import Buffer from "./buffer";
 import type { Loc } from "./buffer";
 import * as n from "./node";
-import { isProgram, isFile, isEmptyStatement } from "@babel/types";
 import type * as t from "@babel/types";
 import type {
   RecordAndTuplePluginOptions,
@@ -504,45 +503,48 @@ class Printer {
     }
   }
 
-  print(node: t.Node | null, parent?: t.Node) {
+  print(node: t.Node | null, parent?: t.Node, noLineTerminator?: boolean) {
     if (!node) return;
 
-    const oldConcise = this.format.concise;
+    const nodeType = node.type;
+    const format = this.format;
+
+    const oldConcise = format.concise;
     if (
       // @ts-expect-error document _compact AST properties
       node._compact
     ) {
-      this.format.concise = true;
+      format.concise = true;
     }
 
     const printMethod =
       this[
-        node.type as Exclude<
+        nodeType as Exclude<
           t.Node["type"],
           // removed
           | "Noop"
           // renamed
           | t.DeprecatedAliases["type"]
         >
       ];
-    if (!printMethod) {
+    if (printMethod === undefined) {
       throw new ReferenceError(
         `unknown node of type ${JSON.stringify(
-          node.type,
-        )} with constructor ${JSON.stringify(node?.constructor.name)}`,
+          nodeType,
+        )} with constructor ${JSON.stringify(node.constructor.name)}`,
       );
     }
 
     this._printStack.push(node);
 
     const oldInAux = this._insideAux;
-    this._insideAux = !node.loc;
+    this._insideAux = node.loc == undefined;
     this._maybeAddAuxComment(this._insideAux && !oldInAux);
 
     let shouldPrintParens: boolean;
     if (
-      this.format.retainFunctionParens &&
-      node.type === "FunctionExpression" &&
+      format.retainFunctionParens &&
+      nodeType === "FunctionExpression" &&
       node.extra &&
       node.extra.parenthesized
     ) {
@@ -554,18 +556,24 @@ class Printer {
 
     this._printLeadingComments(node);
 
-    const loc = isProgram(node) || isFile(node) ? null : node.loc;
+    const loc = nodeType === "Program" || nodeType === "File" ? null : node.loc;
 
     this.withSource("start", loc, printMethod.bind(this, node, parent));
 
-    this._printTrailingComments(node);
+    if (noLineTerminator && !this._noLineTerminator) {
+      this._noLineTerminator = true;
+      this._printTrailingComments(node);
+      this._noLineTerminator = false;
+    } else {
+      this._printTrailingComments(node);
+    }
 
     if (shouldPrintParens) this.token(")");
 
     // end
     this._printStack.pop();
 
-    this.format.concise = oldConcise;
+    format.concise = oldConcise;
     this._insideAux = oldInAux;
   }
 
@@ -667,7 +675,7 @@ class Printer {
   printBlock(parent: Extract<t.Node, { body: t.Statement }>) {
     const node = parent.body;
 
-    if (!isEmptyStatement(node)) {
+    if (node.type !== "EmptyStatement") {
       this.space();
     }
 

packages/babel-generator/test/fixtures/typescript/types-arrow-return-with-comment/input.js → packages/babel-generator/test/fixtures/flow/type-with-comment/input.js

@@ -1 +1,3 @@
 export default (): void /* hi! */ => {};
+
+const foo: any /* Hi! */[] = [];

packages/babel-generator/test/fixtures/flow/type-with-comment/output.js

@@ -0,0 +1,2 @@
+export default ((): void /* hi! */ => {});
+const foo: any /* Hi! */[] = [];

packages/babel-generator/test/fixtures/typescript/type-with-comment/input.js

@@ -0,0 +1,3 @@
+export default (): void /* hi! */ => {};
+
+const foo: any /* Hi! */[] = [];

packages/babel-generator/test/fixtures/typescript/type-with-comment/output.js

@@ -0,0 +1,2 @@
+export default ((): void /* hi! */ => {});
+const foo: any /* Hi! */[] = [];

packages/babel-generator/test/fixtures/typescript/types-with-comments-retainLines/input.js

@@ -0,0 +1,23 @@
+type T = U.
+/* 1 */
+C /* 2 */ [
+  /* 3 */
+  0];
+
+type T2 = U.
+/* 1 */
+C /* 2 */ [
+  /* 3 */
+];
+
+type T3 = U.
+/* 1 */
+C /* 2 */ <
+  /* 3 */
+  0>;
+
+let f = (x)
+/* 1 */
+:
+/* 2 */
+void /* 3 */ => 1

packages/babel-generator/test/fixtures/typescript/types-with-comments-retainLines/options.json

@@ -0,0 +1,3 @@
+{
+  "retainLines": true
+}

packages/babel-generator/test/fixtures/typescript/types-with-comments-retainLines/output.js

@@ -0,0 +1,23 @@
+type T = U.
+/* 1 */
+C /* 2 */[
+/* 3 */
+0];
+
+type T2 = U.
+/* 1 */
+C /* 2 */[];
+
+
+
+type T3 = U.
+/* 1 */
+C /* 2 */<
+/* 3 */
+0>;
+
+let f = (x)
+/* 1 */
+:
+/* 2 */
+void /* 3 */ => 1;