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use proc_macro2::Span;
use proc_macro2::TokenStream as TokenStream2;
use quote::ToTokens;
use syn;
pub struct Codegen;
impl Codegen {
fn extract_printable_args<'a>(pat: &'a syn::Pat, extract_target: &mut Vec<&'a syn::Ident>) {
match pat {
syn::Pat::Wild(_) => {
// ignore args without a name
}
syn::Pat::Path(_)
| syn::Pat::Box(_)
| syn::Pat::Ref(_)
| syn::Pat::Lit(_)
| syn::Pat::Range(_)
| syn::Pat::Verbatim(_)
| syn::Pat::Macro(_) => panic!("Unexpected argument pattern: {:?}", pat),
syn::Pat::Ident(ref ident) => {
if ident.ident.to_string() != "self" {
extract_target.push(&ident.ident);
}
}
syn::Pat::TupleStruct(ref tuple_struct) => {
for pat in tuple_struct.pat.front.iter() {
Self::extract_printable_args(pat, extract_target);
}
for pat in tuple_struct.pat.back.iter() {
Self::extract_printable_args(pat, extract_target);
}
}
syn::Pat::Tuple(ref tuple) => {
for pat in tuple.front.iter() {
Self::extract_printable_args(pat, extract_target);
}
for pat in tuple.back.iter() {
Self::extract_printable_args(pat, extract_target);
}
}
syn::Pat::Struct(ref structure) => {
for pat in structure.fields.iter() {
Self::extract_printable_args(&*pat.pat, extract_target);
}
}
syn::Pat::Slice(ref slice) => {
for pat in slice.front.iter() {
Self::extract_printable_args(pat, extract_target);
}
if let Some(ref pat) = slice.middle {
Self::extract_printable_args(&*pat, extract_target);
}
for pat in slice.back.iter() {
Self::extract_printable_args(pat, extract_target);
}
}
}
}
/// Build begin trace statement.
///
/// Output sample:
///
/// ```ignore
/// trace!("{} {}::foo(arg1: {:?}, arg2: {:?})", ">".repeat(..), module_path!(), arg1, arg2);
/// ```
fn build_begin_trace_statement(fn_decl: &syn::FnDecl, fn_name: &str) -> TokenStream2 {
let mut args = vec![];
for fn_arg in fn_decl.inputs.iter() {
match fn_arg {
syn::FnArg::SelfRef(_) | syn::FnArg::SelfValue(_) => {
// ignore self arg
}
syn::FnArg::Captured(ref arg) => {
Self::extract_printable_args(&arg.pat, &mut args);
}
syn::FnArg::Inferred(ref arg_pat) => {
Self::extract_printable_args(arg_pat, &mut args);
}
syn::FnArg::Ignored(_) => {
// ignore ignored arg
}
}
}
let format_args = args
.iter()
.map(|arg_ident| format!("{}: {{:?}}", arg_ident))
.collect::<Vec<_>>()
.join(", ");
let format = format!("{{}} {{}}::{}({})", fn_name, format_args);
quote! {
trace!(#format, ">".repeat(__level * 4), module_path!(), #(#args),*)
}
}
/// Build end trace statement.
///
/// Output sample:
///
/// ```ignore
/// trace!("{} {}::foo = {:?}", "<".repeat(..), module_path!(), __ret);
/// ```
fn build_end_trace_statement(fn_name: &str) -> TokenStream2 {
let format = format!("{{}} {{}}::{} = {{:?}}", fn_name);
quote! {
trace!(#format, "<".repeat(__level * 4), module_path!(), __ret)
}
}
/// Build the return type of the inner closure.
///
/// We should provide type as much as possible to eliminate type inference failure.
fn build_return_type(fn_decl: &syn::FnDecl) -> TokenStream2 {
let ret_type = match &fn_decl.output {
syn::ReturnType::Default => None,
syn::ReturnType::Type(_, ref ret_type) => match **ret_type {
// We don't write the type if the return type is impl trait.
syn::Type::ImplTrait(_) => None,
_ => Some(ret_type),
},
};
match ret_type {
None => syn::token::Underscore::new(Span::call_site()).into_token_stream(),
Some(t) => t.clone().into_token_stream(),
}
}
/// Transform and build a function block.
///
/// Suppose we receive:
/// ```ignore
/// (pub) fn foo<T>(arg1: T, arg2: foo) -> bool where T: bar {
/// ...
/// }
/// ```
///
/// This function will transform it into:
/// ```ignore
/// (pub) fn foo<T>(&self, arg1: T, arg2: foo) -> bool where T: bar {
/// trace!("{} foo(arg1: {:?}, arg2: {:?})", ">".repeat(..), arg1, arg2);
/// let mut __inner = move || {
/// let __inner_ret: bool = {
/// ...
/// };
/// #[allow(unreachable_code)]
/// __inner_ret
/// };
/// let __ret = __inner();
/// trace!("{} foo = {:?}", ">".repeat(..), __ret);
/// __ret
/// }
/// ```
pub fn build_block(decl: &syn::FnDecl, ident: &syn::Ident, impl_type: Option<&syn::Type>, block: &syn::Block) -> TokenStream2 {
let fn_name = {
let impl_type_str = match impl_type {
None => "".to_owned(),
Some(impl_type) => {
format!("{}::", quote!(#impl_type))
}
};
format!("{}{}", impl_type_str, ident)
};
let begin_trace = Self::build_begin_trace_statement(decl, &fn_name);
let end_trace = Self::build_end_trace_statement(&fn_name);
let return_type = Self::build_return_type(decl);
quote! {
{
use trace2;
trace2::FUNC_CALL_LEVEL.with(|level| {
let mut __level = level.get();
__level = __level.saturating_add(1);
level.set(__level);
#begin_trace;
});
let mut __inner = move || {
// Explicitly give types, so that Box<..> can be correctly inferred.
let __inner_ret: #return_type = #block;
#[allow(unreachable_code)]
// This line might be unreachable, mute the warning. See unreachable test.
__inner_ret
};
let __ret = __inner();
trace2::FUNC_CALL_LEVEL.with(|level| {
let mut __level = level.get();
#end_trace;
__level = __level.saturating_sub(1);
level.set(__level);
});
__ret
}
}
}
}