Fix nested type indexing in the windows-metadata reader (#3799)

Author: kennykerr

crates/libs/metadata/src/reader/type_index.rs

@@ -35,8 +35,8 @@ impl TypeIndex {
             }
 
             for map in file.NestedClass() {
-                let inner = file.usize(map, TypeDef::TABLE, 0);
-                let outer = file.usize(map, TypeDef::TABLE, 1);
+                let inner = file.usize(map, NestedClass::TABLE, 0) - 1;
+                let outer = file.usize(map, NestedClass::TABLE, 1) - 1;
                 nested.entry((file_pos, outer)).or_default().push(inner);
             }
         }

crates/tests/libs/metadata/tests/reader.rs

@@ -72,3 +72,44 @@ fn array() {
 
     assert_eq!(field.ty(), Type::ArrayFixed(Box::new(Type::U8), 512));
 }
+
+#[test]
+fn nested() {
+    let index =
+        reader::TypeIndex::read("../../../libs/bindgen/default/Windows.Win32.winmd").unwrap();
+
+    let def = index
+        .types()
+        .find(|def| def.name() == "D3D10_BUFFER_RTV")
+        .unwrap();
+
+    let fields: Vec<reader::Field> = def.fields().collect();
+    assert_eq!(fields.len(), 2);
+
+    assert_eq!(fields[0].name(), "Anonymous1");
+    assert_eq!(fields[1].name(), "Anonymous2");
+
+    assert_eq!(fields[0].ty(), Type::named("", "_Anonymous1_e__Union"));
+    assert_eq!(fields[1].ty(), Type::named("", "_Anonymous2_e__Union"));
+
+    let types: Vec<reader::TypeDef> = index.nested(def).collect();
+    assert_eq!(types.len(), 2);
+
+    assert_eq!(types[0].namespace(), "");
+    assert_eq!(types[1].namespace(), "");
+
+    assert_eq!(types[0].name(), "_Anonymous1_e__Union");
+    assert_eq!(types[1].name(), "_Anonymous2_e__Union");
+
+    let fields: Vec<reader::Field> = types[0].fields().collect();
+    assert_eq!(fields.len(), 2);
+
+    assert_eq!(fields[0].name(), "FirstElement");
+    assert_eq!(fields[1].name(), "ElementOffset");
+
+    let fields: Vec<reader::Field> = types[1].fields().collect();
+    assert_eq!(fields.len(), 2);
+
+    assert_eq!(fields[0].name(), "NumElements");
+    assert_eq!(fields[1].name(), "ElementWidth");
+}