1 // SPDX-License-Identifier: Apache-2.0 OR MIT 2 3 use proc_macro2::TokenStream; 4 use quote::quote; 5 use syn::{parse::Nothing, parse_quote, spanned::Spanned, ImplItem, ItemImpl, Token}; 6 7 use crate::diagnostics::{DiagCtxt, ErrorGuaranteed}; 8 9 pub(crate) fn pinned_drop( 10 _args: Nothing, 11 mut input: ItemImpl, 12 dcx: &mut DiagCtxt, 13 ) -> Result<TokenStream, ErrorGuaranteed> { 14 if let Some(unsafety) = input.unsafety { 15 dcx.error(unsafety, "implementing `PinnedDrop` is safe"); 16 } 17 input.unsafety = Some(Token); 18 match &mut input.trait_ { 19 Some((not, path, _for)) => { 20 if let Some(not) = not { 21 dcx.error(not, "cannot implement `!PinnedDrop`"); 22 } 23 for (seg, expected) in path 24 .segments 25 .iter() 26 .rev() 27 .zip(["PinnedDrop", "pin_init", ""]) 28 { 29 if expected.is_empty() || seg.ident != expected { 30 dcx.error(seg, "bad import path for `PinnedDrop`"); 31 } 32 if !seg.arguments.is_none() { 33 dcx.error(&seg.arguments, "unexpected arguments for `PinnedDrop` path"); 34 } 35 } 36 *path = parse_quote!(::pin_init::PinnedDrop); 37 } 38 None => { 39 let span = input 40 .impl_token 41 .span 42 .join(input.self_ty.span()) 43 .unwrap_or(input.impl_token.span); 44 dcx.error( 45 span, 46 "expected `impl ... PinnedDrop for ...`, got inherent impl", 47 ); 48 } 49 } 50 for item in &mut input.items { 51 if let ImplItem::Fn(fn_item) = item { 52 if fn_item.sig.ident == "drop" { 53 fn_item 54 .sig 55 .inputs 56 .push(parse_quote!(_: ::pin_init::__internal::OnlyCallFromDrop)); 57 } 58 } 59 } 60 Ok(quote!(#input)) 61 } 62