From b4ea47d23e88b6bd9859b10daf3f482290379a90 Mon Sep 17 00:00:00 2001
From: sinkuu <sinkuu@sinkuu.xyz>
Date: Wed, 18 Oct 2017 07:29:47 +0900
Subject: [PATCH 1/2] Detect proc-macro in needless_pass_by_value

Fixes #1876
---
 clippy_lints/src/needless_pass_by_value.rs | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/clippy_lints/src/needless_pass_by_value.rs b/clippy_lints/src/needless_pass_by_value.rs
index 3c1f6ef2c4bc..bc54d4ebe5fb 100644
--- a/clippy_lints/src/needless_pass_by_value.rs
+++ b/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`)

From 9221bd9c97047d9eac21867f5a11651080e2b88f Mon Sep 17 00:00:00 2001
From: sinkuu <sinkuu@sinkuu.xyz>
Date: Wed, 18 Oct 2017 14:06:38 +0900
Subject: [PATCH 2/2] Add test

---
 mini-macro/src/lib.rs              | 28 +++++++++++++++++++++++-----
 tests/run-pass/procedural_macro.rs |  1 +
 2 files changed, 24 insertions(+), 5 deletions(-)

diff --git a/mini-macro/src/lib.rs b/mini-macro/src/lib.rs
index fda167b69c70..67337afd3e70 100644
--- a/mini-macro/src/lib.rs
+++ b/mini-macro/src/lib.rs
@@ -1,13 +1,15 @@
-#![feature(plugin_registrar, rustc_private)]
+#![feature(plugin_registrar, rustc_private, quote)]
 
 extern crate rustc_plugin;
 extern crate syntax;
 
-use syntax::codemap::Span;
-use syntax::tokenstream::TokenTree;
-use syntax::ext::base::{ExtCtxt, MacEager, MacResult};
-use syntax::ext::build::AstBuilder; // trait for expr_usize
 use rustc_plugin::Registry;
+use syntax::ast::MetaItem;
+use syntax::codemap::Span;
+use syntax::ext::base::{Annotatable, ExtCtxt, MacEager, MacResult, SyntaxExtension};
+use syntax::ext::build::AstBuilder; // trait for expr_usize
+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);
@@ -15,7 +17,23 @@ fn expand_macro(cx: &mut ExtCtxt, sp: Span, _: &[TokenTree]) -> Box<MacResult +
     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)),
+    );
 }
diff --git a/tests/run-pass/procedural_macro.rs b/tests/run-pass/procedural_macro.rs
index b185f6dc4277..f52c778a49dc 100644
--- a/tests/run-pass/procedural_macro.rs
+++ b/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!();
 }