Merge pull request #2148 from sinkuu/proc_macro

needless_pass_by_value false-positive in annotation

Author: oli-obk

clippy_lints/src/needless_pass_by_value.rs

@@ -121,6 +121,11 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for NeedlessPassByValue {
             .zip(&body.arguments)
             .enumerate()
         {
+            // All spans generated from a proc-macro invocation are the same...
+            if span == input.span {
+                return;
+            }
+
             // * Exclude a type that is specifically bounded by `Borrow`.
             // * Exclude a type whose reference also fulfills its bound.
             //   (e.g. `std::convert::AsRef`, `serde::Serialize`)

mini-macro/src/lib.rs

@@ -1,21 +1,39 @@
-#![feature(plugin_registrar, rustc_private)]
+#![feature(plugin_registrar, rustc_private, quote)]
 
 extern crate rustc_plugin;
 extern crate syntax;
 
+use rustc_plugin::Registry;
+use syntax::ast::MetaItem;
 use syntax::codemap::Span;
-use syntax::tokenstream::TokenTree;
-use syntax::ext::base::{ExtCtxt, MacEager, MacResult};
+use syntax::ext::base::{Annotatable, ExtCtxt, MacEager, MacResult, SyntaxExtension};
 use syntax::ext::build::AstBuilder; // trait for expr_usize
-use rustc_plugin::Registry;
+use syntax::symbol::Symbol;
+use syntax::tokenstream::TokenTree;
 
 fn expand_macro(cx: &mut ExtCtxt, sp: Span, _: &[TokenTree]) -> Box<MacResult + 'static> {
     let e = cx.expr_usize(sp, 42);
     let e = cx.expr_mut_addr_of(sp, e);
     MacEager::expr(cx.expr_mut_addr_of(sp, e))
 }
 
+fn expand_attr_macro(cx: &mut ExtCtxt, _: Span, _: &MetaItem, annotated: Annotatable) -> Vec<Annotatable> {
+    vec![
+        Annotatable::Item(
+            quote_item!(
+                cx,
+                #[allow(unused)] fn needless_take_by_value(s: String) { println!("{}", s.len()); }
+            ).unwrap()
+        ),
+        annotated,
+    ]
+}
+
 #[plugin_registrar]
 pub fn plugin_registrar(reg: &mut Registry) {
     reg.register_macro("mini_macro", expand_macro);
+    reg.register_syntax_extension(
+        Symbol::intern("mini_macro_attr"),
+        SyntaxExtension::MultiModifier(Box::new(expand_attr_macro)),
+    );
 }

tests/run-pass/procedural_macro.rs

@@ -2,6 +2,7 @@
 #![plugin(clippy_mini_macro_test)]
 
 #[deny(warnings)]
+#[mini_macro_attr]
 fn main() {
     let _ = mini_macro!();
 }