From 57b6256b780cd8813addeb169ccccefcbdfea8c1 Mon Sep 17 00:00:00 2001
From: IdanArye <IdanArye@gmail.com>
Date: Fri, 22 Sep 2023 01:33:32 +0300
Subject: [PATCH] Fix #118: Use generics with the constructor in `build` method

---
 CHANGELOG.md                           |  3 +++
 tests/tests.rs                         | 21 +++++++++++++++++++++
 typed-builder-macro/src/struct_info.rs |  8 +++++++-
 3 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9220d555..2eee9600 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,9 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ## [Unreleased]
 
+### Fixed
+- Use generics with the constructor in `build` method (see issue #118)
+
 ## 0.16.1 - 2023-09-18
 ### Fixed
 - Add `#[allow(clippy::exhaustive_enums)]` to generated empty enums used for
diff --git a/tests/tests.rs b/tests/tests.rs
index 0a84be96..44cba043 100644
--- a/tests/tests.rs
+++ b/tests/tests.rs
@@ -779,3 +779,24 @@ fn test_prefix_and_suffix() {
     let foo = Foo::builder().with_x_value(1).with_y_value(2).build();
     assert_eq!(foo, Foo { x: 1, y: 2 })
 }
+
+#[test]
+fn test_issue_118() {
+    #[derive(TypedBuilder)]
+    #[builder(build_method(into=Bar))]
+    struct Foo<T> {
+        #[builder(default, setter(skip))]
+        #[allow(dead_code)]
+        foo: Option<T>,
+    }
+
+    struct Bar;
+
+    impl<T> From<Foo<T>> for Bar {
+        fn from(_value: Foo<T>) -> Self {
+            Self
+        }
+    }
+
+    let _ = Foo::<u32>::builder().build();
+}
diff --git a/typed-builder-macro/src/struct_info.rs b/typed-builder-macro/src/struct_info.rs
index b245d22c..c77c9754 100644
--- a/typed-builder-macro/src/struct_info.rs
+++ b/typed-builder-macro/src/struct_info.rs
@@ -483,6 +483,12 @@ impl<'a> StructInfo<'a> {
         } else {
             quote!()
         };
+
+        let type_constructor = {
+            let ty_generics = ty_generics.as_turbofish();
+            quote!(#name #ty_generics)
+        };
+
         let (build_method_generic, output_type, build_method_where_clause) = match &self.builder_attr.build_method.into {
             IntoSetting::NoConversion => (None, quote!(#name #ty_generics), None),
             IntoSetting::GenericConversion => (
@@ -504,7 +510,7 @@ impl<'a> StructInfo<'a> {
                     #( #assignments )*
 
                     #[allow(deprecated)]
-                    #name {
+                    #type_constructor {
                         #( #field_names ),*
                     }.into()
                 }