Suppress clippy::too_many_arguments in generated code

This is generally not something users can do anything to fix. This
commit suppresses it if a generated function as > 5 arguments.

Fixes #2

Author: swlynch99

src/substruct.rs

@@ -185,17 +185,18 @@ impl<'a> Emitter<'a> {
         let name = &substruct.ident;
         let (impl_generics, ty_generics, where_clause) = substruct.generics.split_for_impl();
 
+        let mut attrs = Vec::<syn::Attribute>::new();
         let method = syn::Ident::new(
             &format!("into_{}", self.input.ident.to_string().to_snake_case()),
             Span::call_site(),
         );
-        let doc: syn::Attribute = syn::parse_quote!(
+        attrs.push(syn::parse_quote!(
             #[doc = concat!("Convert `self` into a [`", stringify!(#original), "`].")]
-        );
+        ));
 
         let fields = match &self.input.data {
             syn::Data::Enum(_) => panic!("Attempted to emit conversions for an enum"),
-            // Emitting conversions for an enum doesn't make sense
+            // Emitting conversions for a union doesn't make sense
             syn::Data::Union(_) => return,
             // Unit structs have no fields and so they have no conversions
             syn::Data::Struct(data) if matches!(data.fields, syn::Fields::Unit) => return,
@@ -238,11 +239,15 @@ impl<'a> Emitter<'a> {
             .collect();
         let exc: Vec<_> = excluded.keys().collect();
 
+        if args.len() > 5 {
+            attrs.push(syn::parse_quote!(#[allow(clippy::too_many_arguments)]))
+        }
+
         self.tokens.extend(quote::quote! {
             impl #impl_generics #name #ty_generics
             #where_clause
             {
-                #doc
+                #( #attrs )*
                 pub fn #method(self, #( #args: #types, )*) -> #original #ty_generics {
                     #original {
                         #( #inc_dst: self.#inc_src, )*

tests/trybuild.rs

@@ -1,5 +1,9 @@
 #[test]
 fn trybuild() {
+    // This still compiles the crate normally, it just means that we also get
+    // clippy warnings as well.
+    std::env::set_var("RUSTC_WORKSPACE_WRAPPER", "clippy-driver");
+
     let t = trybuild::TestCases::new();
     t.compile_fail("tests/ui/fail/*.rs");
     t.pass("tests/ui/pass/*.rs");

tests/ui/fail/union-invalid-field.stderr

@@ -6,8 +6,9 @@ error[E0609]: no field `y` on type `C`
    |
 help: a field with a similar name exists
    |
-15 |     value.x = 1;
-   |           ~
+15 -     value.y = 1;
+15 +     value.x = 1;
+   |
 
 error[E0609]: no field `z` on type `C`
   --> tests/ui/fail/union-invalid-field.rs:16:11
@@ -17,5 +18,6 @@ error[E0609]: no field `z` on type `C`
    |
 help: a field with a similar name exists
    |
-16 |     value.x = 1;
-   |           ~
+16 -     value.z = 1;
+16 +     value.x = 1;
+   |

tests/ui/pass/large-struct.rs

@@ -0,0 +1,29 @@
+#![deny(clippy::too_many_arguments)]
+#![allow(dead_code)]
+
+use substruct::substruct;
+
+#[substruct(A, B)]
+struct Large {
+    #[substruct(B)]
+    pub v0: u32,
+    #[substruct(B)]
+    pub v1: u32,
+    #[substruct(B)]
+    pub v2: u32,
+    #[substruct(B)]
+    pub v3: u32,
+    #[substruct(B)]
+    pub v4: u32,
+    #[substruct(B)]
+    pub v5: u32,
+    #[substruct(B)]
+    pub v6: u32,
+    #[substruct(B)]
+    pub v7: u32,
+    #[substruct(B)]
+    pub v8: u32,
+    pub v9: u32,
+}
+
+fn main() {}