Stop checking invalid properties

src/language-js/parse/babel.js

@@ -187,7 +187,6 @@ const allowedMessageCodes = new Set([
   "ConstructorHasTypeParameters",
 
   "UnsupportedParameterPropertyKind",
-  "UnexpectedParameterModifier",
 
   "MixedLabeledAndUnlabeledElements",
   "InvalidTupleMemberLabel",

src/language-js/parse/postprocess/typescript.js

@@ -2,11 +2,16 @@ import isNonEmptyArray from "../../../utils/is-non-empty-array.js";
 import visitNode from "./visit-node.js";
 import throwTsSyntaxError from "./throw-ts-syntax-error.js";
 
+/** @type {import("typescript")} */
 let ts;
 
 function getTsNodeLocation(nodeOrToken) {
-  const sourceFile = ts.getSourceFileOfNode(nodeOrToken);
-  const position = ts.rangeOfNode(nodeOrToken);
+  const sourceFile =
+    // @ts-expect-error -- internal?
+    ts.getSourceFileOfNode(nodeOrToken);
+  const position =
+    // @ts-expect-error -- internal?
+    ts.rangeOfNode(nodeOrToken);
   const [start, end] = [position.pos, position.end].map((position) => {
     const { line, character: column } =
       sourceFile.getLineAndCharacterOfPosition(position);
@@ -110,6 +115,24 @@ function throwErrorForInvalidModifier(node) {
       );
     }
 
+    if (
+      (modifier.kind === SyntaxKind.InKeyword ||
+        modifier.kind === SyntaxKind.OutKeyword) &&
+      (node.kind !== SyntaxKind.TypeParameter ||
+        !(
+          ts.isInterfaceDeclaration(node.parent) ||
+          ts.isClassLike(node.parent) ||
+          ts.isTypeAliasDeclaration(node.parent)
+        ))
+    ) {
+      throwErrorOnTsNode(
+        modifier,
+        `'${ts.tokenToString(
+          modifier.kind
+        )}' modifier can only appear on a type parameter of a class, interface or type alias`
+      );
+    }
+
     if (
       modifier.kind === SyntaxKind.ReadonlyKeyword &&
       node.kind !== SyntaxKind.PropertyDeclaration &&
@@ -189,6 +212,45 @@ function throwErrorForInvalidModifier(node) {
     ) {
       throwErrorOnTsNode(modifier, "'async' modifier cannot be used here.");
     }
+
+    // `checkGrammarModifiers` function in `typescript`
+    if (
+      node.kind === SyntaxKind.Parameter &&
+      (modifier.kind === SyntaxKind.StaticKeyword ||
+        modifier.kind === SyntaxKind.ExportKeyword ||
+        modifier.kind === SyntaxKind.DeclareKeyword ||
+        modifier.kind === SyntaxKind.AsyncKeyword)
+    ) {
+      throwErrorOnTsNode(
+        modifier,
+        `'${ts.tokenToString(
+          modifier.kind
+        )}' modifier cannot appear on a parameter.`
+      );
+    }
+
+    // `checkParameter` function in `typescript`
+    if (
+      node.kind === SyntaxKind.Parameter &&
+      // @ts-expect-error -- internal?
+      ts.hasSyntacticModifier(node, ts.ModifierFlags.ParameterPropertyModifier)
+    ) {
+      const func =
+        // @ts-expect-error -- internal?
+        ts.getContainingFunction(node);
+      if (
+        !(
+          func.kind === SyntaxKind.Constructor &&
+          // @ts-expect-error -- internal?
+          ts.nodeIsPresent(func.body)
+        )
+      ) {
+        throwErrorOnTsNode(
+          modifier,
+          "A parameter property is only allowed in a constructor implementation."
+        );
+      }
+    }
   }
 }
 

src/language-js/print/typescript.js

@@ -171,23 +171,14 @@ function printTypescript(path, options, print) {
       ];
 
     case "TSParameterProperty":
-      parts.push(printTypeScriptAccessibilityToken(node));
-      if (node.export) {
-        parts.push("export ");
-      }
-      if (node.static) {
-        parts.push("static ");
-      }
-      if (node.override) {
-        parts.push("override ");
-      }
-      if (node.readonly) {
-        parts.push("readonly ");
-      }
-
-      parts.push(print("parameter"));
+      return [
+        printTypeScriptAccessibilityToken(node),
+        node.static ? "static " : "",
+        node.override ? "override " : "",
+        node.readonly ? "readonly " : "",
+        print("parameter"),
+      ];
 
-      return parts;
     case "TSTypeQuery":
       return ["typeof ", print("exprName"), print("typeParameters")];
     case "TSIndexSignature": {
@@ -212,7 +203,6 @@ function printTypescript(path, options, print) {
       ]);
 
       return [
-        node.export ? "export " : "",
         printTypeScriptAccessibilityToken(node),
         node.static ? "static " : "",
         node.readonly ? "readonly " : "",

src/language-js/traverse/visitor-keys.evaluate.js

@@ -50,6 +50,9 @@ const additionalVisitorKeys = {
 };
 
 const excludeKeys = {
+  // From `tsVisitorKeys`
+  MethodDefinition: ["typeParameters"],
+
   // From `flowVisitorKeys`
   ArrowFunctionExpression: ["id"],
   DeclareOpaqueType: ["impltype"],