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Merge pull request #753 from mystor/patch-1

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Update usage of `syn` in Procedural Macros chapter
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Steve Klabnik
2017-06-07 10:46:27 -04:00
committed by GitHub
parent 7a999ef48f 94946f20ce
commit c507dbb4e5
1 changed files with 5 additions and 5 deletions
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10
first-edition/src/procedural-macros.md
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@@ -153,7 +153,7 @@ In this case, we're keeping it as simple as possible.
Great, so let's write `impl_hello_world(&ast)`.
```rust,ignore
fn impl_hello_world(ast: &syn::MacroInput) -> quote::Tokens {
fn impl_hello_world(ast: &syn::DeriveInput) -> quote::Tokens {
let name = &ast.ident;
quote! {
impl HelloWorld for #name {
@@ -167,7 +167,7 @@ fn impl_hello_world(ast: &syn::MacroInput) -> quote::Tokens {
So this is where quotes comes in. The `ast` argument is a struct that gives us
a representation of our type (which can be either a `struct` or an `enum`).
Check out the [docs](https://docs.rs/syn/0.10.5/syn/struct.MacroInput.html),
Check out the [docs](https://docs.rs/syn/0.11.11/syn/struct.DeriveInput.html),
there is some useful information there. We are able to get the name of the
type using `ast.ident`. The `quote!` macro lets us write up the Rust code
that we wish to return and convert it into `Tokens`. `quote!` lets us use some
@@ -181,8 +181,8 @@ So I think that's it. Oh, well, we do need to add dependencies for `syn` and
```toml
[dependencies]
syn = "0.10.5"
quote = "0.3.10"
syn = "0.11.11"
quote = "0.3.15"
```
That should be it. Let's try to compile `hello-world`.
@@ -254,7 +254,7 @@ But how do we tell the user, that we do not accept enums?
The idiomatic way to report errors in procedural macros is to panic:
```rust,ignore
fn impl_hello_world(ast: &syn::MacroInput) -> quote::Tokens {
fn impl_hello_world(ast: &syn::DeriveInput) -> quote::Tokens {
let name = &ast.ident;
// Check if derive(HelloWorld) was specified for a struct
if let syn::Body::Struct(_) = ast.body {