Merge #37

37: Remove support of if-let expressions from #[project] attribute r=taiki-e a=taiki-e

This has many limitations.

cc #36

Co-authored-by: Taiki Endo <[email protected]>

pin-project-internal/src/project.rs

@@ -46,7 +46,6 @@ impl Replace for Local {
 impl Replace for Expr {
     fn replace(&mut self, register: &mut Register) {
         match self {
-            Expr::If(expr) => expr.replace(register),
             Expr::ForLoop(ExprForLoop { pat, .. }) => pat.replace(register),
             Expr::Let(ExprLet { pats, .. }) => pats.replace(register),
 
@@ -73,16 +72,6 @@ impl Replace for Expr {
     }
 }
 
-impl Replace for ExprIf {
-    fn replace(&mut self, register: &mut Register) {
-        self.cond.replace(register);
-
-        if let Some(Expr::If(expr)) = self.else_branch.as_mut().map(|(_, expr)| &mut **expr) {
-            expr.replace(register);
-        }
-    }
-}
-
 impl Replace for Punctuated<Pat, Or> {
     fn replace(&mut self, register: &mut Register) {
         self.iter_mut().for_each(|pat| pat.replace(register));

src/lib.rs

@@ -157,6 +157,8 @@
 ///
 /// ## Examples
 ///
+/// The following two syntaxes are supported.
+///
 /// ### `let` bindings
 ///
 /// ```rust
@@ -212,37 +214,6 @@
 ///     }
 /// }
 /// ```
-///
-/// ### `if let` expressions
-///
-/// When used against `if let` expressions, the `#[project]` attribute records
-/// the name of the structure destructed with the first `if let`. Destructing
-/// different structures in the after second times will not generate wrong code.
-///
-/// ```rust
-/// use pin_project::{project, pin_projectable};
-/// # use std::pin::Pin;
-///
-/// #[pin_projectable]
-/// enum Foo<A, B, C> {
-///     Tuple(#[pin] A, B),
-///     Struct { field: C },
-///     Unit,
-/// }
-///
-/// impl<A, B, C> Foo<A, B, C> {
-///     #[project] // Nightly does not need a dummy attribute to the function.
-///     fn baz(self: Pin<&mut Self>) {
-///         #[project]
-///         {
-///             if let Foo::Tuple(x, y) = self.project() {
-///                 let _: Pin<&mut A> = x;
-///                 let _: &mut B = y;
-///             }
-///         }
-///     }
-/// }
-/// ```
 #[cfg(feature = "project_attr")]
 #[doc(inline)]
 pub use pin_project_internal::project;

tests/project.rs

@@ -79,17 +79,4 @@ fn test_project_attr() {
         }
         Baz::None => {}
     }
-
-    #[project]
-    {
-        if let Baz::Variant1(x, y) = baz {
-            let x: Pin<&mut i32> = x;
-            assert_eq!(*x, 1);
-
-            let y: &mut i32 = y;
-            assert_eq!(*y, 2);
-        } else if let Option::Some(_) = Some(1) {
-            // Check that don't replace different types by mistake
-        }
-    }
 }