Fall back from globalReadonlyArrayType to globalArrayType when transpiling

src/compiler/checker.ts

@@ -30307,7 +30307,7 @@ namespace ts {
                 autoArrayType = createAnonymousType(undefined, emptySymbols, emptyArray, emptyArray, undefined, undefined);
             }
 
-            globalReadonlyArrayType = <GenericType>getGlobalTypeOrUndefined("ReadonlyArray" as __String, /*arity*/ 1);
+            globalReadonlyArrayType = <GenericType>getGlobalTypeOrUndefined("ReadonlyArray" as __String, /*arity*/ 1) || globalArrayType;
             anyReadonlyArrayType = globalReadonlyArrayType ? createTypeFromGenericGlobalType(globalReadonlyArrayType, [anyType]) : anyArrayType;
             globalThisType = <GenericType>getGlobalTypeOrUndefined("ThisType" as __String, /*arity*/ 1);
 

src/testRunner/unittests/services/transpile.ts

@@ -445,5 +445,13 @@ var x = 0;`, {
                 }
             }
         });
+
+        transpilesCorrectly("Supports readonly keyword for arrays", "let x: readonly string[];", {
+            options: { compilerOptions: { module: ModuleKind.CommonJS } }
+        });
+
+        transpilesCorrectly("Supports 'as const' arrays", `([] as const).forEach(k => console.log(k));`, {
+            options: { compilerOptions: { module: ModuleKind.CommonJS } }
+        });
     });
 }