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annotate #[allow(unreachable_code)] to tail expr #43

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annotate #[allow(unreachable_code)] to tail expr #43

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58eb203
annotate #[allow(unreachable_code)] to tail expr
ubnt-intrepid Apr 18, 2020
f3ab630
keep attributes when the tail expr is explicit
ubnt-intrepid Apr 18, 2020
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57 changes: 51 additions & 6 deletions fehler-macros/src/throws.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -102,7 +102,7 @@ impl Fold for Throws {
fn fold_expr_return(&mut self, i: syn::ExprReturn) -> syn::ExprReturn {
let ok = match &i.expr {
Some(expr) => ok(expr),
None => ok_unit(),
None => ok_unit(false),
};
syn::ExprReturn { expr: Some(Box::new(ok)), ..i }
}
Expand All @@ -117,13 +117,30 @@ fn modify_tail(is_unit_fn: bool, stmts: &mut Vec<syn::Stmt>) {
let new = syn::parse2(quote::quote!(#e;)).unwrap();
stmts.pop();
stmts.push(new);
stmts.push(syn::Stmt::Expr(ok_unit()));
stmts.push(syn::Stmt::Expr(ok_unit(true)));
}
Some(syn::Stmt::Expr(e)) => {
*e = ok(e);
// In this case, it is necessary to keep the original attributes
// before wrapping the expression. The generated code will have
// attributes attached outside of Ok-wrapping as follows:
//
// // from
// #[allow(unreachable_code, ...)]
// tail_expr
//
// // to
// #[allow(unreachable_code, ...)]
// <_ as ::fehler::__internal::_Succeed>::from_ok(tail_expr)
//
let attrs = take_attrs(e);
let ok = ok(e);
*e = syn::Expr::Verbatim(quote::quote! {
#(#attrs)*
#ok
});
}
_ if is_unit_fn => {
stmts.push(syn::Stmt::Expr(ok_unit()));
stmts.push(syn::Stmt::Expr(ok_unit(true)));
}
_ => { }
}
Expand All @@ -145,6 +162,34 @@ fn ok(expr: &syn::Expr) -> syn::Expr {
syn::parse2(quote::quote!(<_ as ::fehler::__internal::_Succeed>::from_ok(#expr))).unwrap()
}

fn ok_unit() -> syn::Expr {
syn::parse2(quote::quote!(<_ as ::fehler::__internal::_Succeed>::from_ok(()))).unwrap()
fn ok_unit(with_attr: bool) -> syn::Expr {
let attr = if with_attr {
Some(quote::quote!( #[allow(unreachable_code)] ))
} else {
None
};
syn::parse2(quote::quote! {
#attr
<_ as ::fehler::__internal::_Succeed>::from_ok(())
}).unwrap()
}

fn take_attrs(e: &mut syn::Expr) -> Vec<syn::Attribute> {
macro_rules! body {
($($Variant:ident),*) => {
match e {
$(
syn::Expr::$Variant(e) => e.attrs.drain(..).collect(),
)*
_ => unreachable!(),
}
}
}
body!(
Array, Assign, AssignOp, Async, Await, Binary, Block,
Box, Break, Call, Cast, Closure, Continue, Field, ForLoop,
Group, If, Index, Let, Lit, Loop, Macro, Match, MethodCall,
Paren, Path, Range, Reference, Repeat, Return, Struct,
Try, TryBlock, Tuple, Type, Unary, Unsafe, While, Yield
)
}