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bind the value of tail expr before Ok-wrarpping #46

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Merged
withoutboats merged 1 commit into from
Apr 27, 2020
Merged

bind the value of tail expr before Ok-wrarpping #46

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56 changes: 15 additions & 41 deletions fehler-macros/src/throws.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -37,35 +37,33 @@ impl Throws {
}

impl Fold for Throws {
fn fold_item_fn(&mut self, mut i: syn::ItemFn) -> syn::ItemFn {
fn fold_item_fn(&mut self, i: syn::ItemFn) -> syn::ItemFn {
if !self.outer_fn { return i; }
self.outer_fn = false;

modify_tail(is_unit_fn(&i.sig.output), &mut i.block.stmts);

let sig = syn::Signature {
output: self.fold_return_type(i.sig.output),
..i.sig
};


let block = Box::new(self.fold_block(*i.block));
let inner = self.fold_block(*i.block);
let block = Box::new(make_fn_block(&inner));

syn::ItemFn { sig, block, ..i }
}

fn fold_impl_item_method(&mut self, mut i: syn::ImplItemMethod) -> syn::ImplItemMethod {
fn fold_impl_item_method(&mut self, i: syn::ImplItemMethod) -> syn::ImplItemMethod {
if !self.outer_fn { return i; }
self.outer_fn = false;

modify_tail(is_unit_fn(&i.sig.output), &mut i.block.stmts);

let sig = syn::Signature {
output: self.fold_return_type(i.sig.output),
..i.sig
};

let block = self.fold_block(i.block);
let inner = self.fold_block(i.block);
let block = make_fn_block(&inner);

syn::ImplItemMethod { sig, block, ..i }
}
Expand All @@ -74,9 +72,9 @@ impl Fold for Throws {
if !self.outer_fn { return i; }
self.outer_fn = false;

let default = i.default.take().map(|mut block| {
modify_tail(is_unit_fn(&i.sig.output), &mut block.stmts);
self.fold_block(block)
let default = i.default.take().map(|block| {
let inner = self.fold_block(block);
make_fn_block(&inner)
});

let sig = syn::Signature {
Expand Down Expand Up @@ -108,37 +106,13 @@ impl Fold for Throws {
}
}

fn modify_tail(is_unit_fn: bool, stmts: &mut Vec<syn::Stmt>) {
let last_non_item_stmt = stmts.iter_mut().rev().filter(|s| {
if let syn::Stmt::Item(_) = s { false } else { true }
}).next();
match last_non_item_stmt {
Some(syn::Stmt::Expr(e)) if is_unit_fn => {
let new = syn::parse2(quote::quote!(#e;)).unwrap();
stmts.pop();
stmts.push(new);
stmts.push(syn::Stmt::Expr(ok_unit()));
}
Some(syn::Stmt::Expr(e)) => {
*e = ok(e);
}
_ if is_unit_fn => {
stmts.push(syn::Stmt::Expr(ok_unit()));
}
_ => { }
}
}

fn make_fn_block(inner: &syn::Block) -> syn::Block {
syn::parse2(quote::quote! {{
let __ret = #inner;

fn is_unit_fn(i: &syn::ReturnType) -> bool {
match i {
syn::ReturnType::Default => true,
syn::ReturnType::Type(_, ty) => {
if let syn::Type::Tuple(syn::TypeTuple { elems, .. }) = &**ty {
elems.is_empty()
} else { false }
}
}
#[allow(unreachable_code)]
<_ as ::fehler::__internal::_Succeed>::from_ok(__ret)
}}).unwrap()
}

fn ok(expr: &syn::Expr) -> syn::Expr {
Expand Down