Fix #2079

Author: Gerrit0

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Unreleased
 
+### Bug Fixes
+
+-   Fixed conversion of intrinsic string mapping types when converting without a type node, #2079.
+
 ## v0.23.17 (2022-10-18)
 
 ### Features

src/lib/converter/types.ts

@@ -644,7 +644,7 @@ const queryConverter: TypeConverter<ts.TypeQueryNode> = {
 
 const referenceConverter: TypeConverter<
     ts.TypeReferenceNode,
-    ts.TypeReference
+    ts.TypeReference | ts.StringMappingType
 > = {
     kind: [ts.SyntaxKind.TypeReference],
     convert(context, node) {
@@ -688,9 +688,17 @@ const referenceConverter: TypeConverter<
             context.resolveAliasedSymbol(symbol),
             context
         );
-        ref.typeArguments = (
-            type.aliasSymbol ? type.aliasTypeArguments : type.typeArguments
-        )?.map((ref) => convertType(context, ref));
+        if (type.flags & ts.TypeFlags.StringMapping) {
+            ref.typeArguments = [
+                convertType(context, (type as ts.StringMappingType).type),
+            ];
+        } else {
+            ref.typeArguments = (
+                type.aliasSymbol
+                    ? type.aliasTypeArguments
+                    : (type as ts.TypeReference).typeArguments
+            )?.map((ref) => convertType(context, ref));
+        }
         return ref;
     },
 };

src/test/converter2/issues/gh2079.ts

@@ -0,0 +1,5 @@
+export function capitalize<T extends string>(string: T) {
+    return (
+        string === "" ? "" : string[0].toUpperCase() + string.slice(1)
+    ) as Capitalize<T>;
+}

src/test/issueTests.ts

@@ -803,4 +803,10 @@ export const issueTests: {
     gh2064(project) {
         query(project, "PrivateCtorDecl.x");
     },
+
+    gh2079(project) {
+        const cap = query(project, "capitalize");
+        const sig = cap.signatures![0];
+        equal(sig.type?.toString(), "Capitalize<T>");
+    },
 };