Lint for trait methods without bodies

CHANGELOG.md

@@ -583,6 +583,7 @@ All notable changes to this project will be documented in this file.
 [`ineffective_bit_mask`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#ineffective_bit_mask
 [`infinite_iter`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#infinite_iter
 [`inline_always`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#inline_always
+[`inline_fn_without_body`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#inline_fn_without_body
 [`int_plus_one`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#int_plus_one
 [`integer_arithmetic`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#integer_arithmetic
 [`invalid_ref`]: https://rust-lang-nursery.github.io/rust-clippy/master/index.html#invalid_ref

clippy_lints/src/inline_fn_without_body.rs

@@ -0,0 +1,65 @@
+//! checks for `#[inline]` on trait methods without bodies
+
+use rustc::lint::*;
+use rustc::hir::*;
+use syntax::ast::{Attribute, Name};
+use utils::span_lint_and_then;
+use utils::sugg::DiagnosticBuilderExt;
+
+/// **What it does:** Checks for `#[inline]` on trait methods without bodies
+///
+/// **Why is this bad?** Only implementations of trait methods may be inlined.
+/// The inline attribute is ignored for trait methods without bodies.
+///
+/// **Known problems:** None.
+///
+/// **Example:**
+/// ```rust
+/// trait Animal {
+///     #[inline]
+///     fn name(&self) -> &'static str;
+/// }
+/// ```
+declare_lint! {
+    pub INLINE_FN_WITHOUT_BODY,
+    Warn,
+    "use of `#[inline]` on trait methods without bodies"
+}
+
+#[derive(Copy, Clone)]
+pub struct Pass;
+
+impl LintPass for Pass {
+    fn get_lints(&self) -> LintArray {
+        lint_array!(INLINE_FN_WITHOUT_BODY)
+    }
+}
+
+impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Pass {
+    fn check_trait_item(&mut self, cx: &LateContext<'a, 'tcx>, item: &'tcx TraitItem) {
+        match item.node {
+            TraitItemKind::Method(_, TraitMethod::Required(_)) => {
+                check_attrs(cx, &item.name, &item.attrs);
+            },
+            _ => {},
+        }
+    }
+}
+
+fn check_attrs(cx: &LateContext, name: &Name, attrs: &[Attribute]) {
+    for attr in attrs {
+        if attr.name().map_or(true, |n| n != "inline") {
+            continue;
+        }
+
+        span_lint_and_then(
+            cx,
+            INLINE_FN_WITHOUT_BODY,
+            attr.span,
+            &format!("use of `#[inline]` on trait method `{}` which has no body", name),
+            |db| {
+                db.suggest_remove_item(cx, attr.span, "remove");
+            },
+        );
+    }
+}

clippy_lints/src/lib.rs

@@ -109,6 +109,7 @@ pub mod identity_op;
 pub mod if_let_redundant_pattern_matching;
 pub mod if_not_else;
 pub mod infinite_iter;
+pub mod inline_fn_without_body;
 pub mod int_plus_one;
 pub mod invalid_ref;
 pub mod is_unit_expr;
@@ -359,6 +360,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
     reg.register_late_lint_pass(box use_self::UseSelf);
     reg.register_late_lint_pass(box bytecount::ByteCount);
     reg.register_late_lint_pass(box infinite_iter::Pass);
+    reg.register_late_lint_pass(box inline_fn_without_body::Pass);
     reg.register_late_lint_pass(box invalid_ref::InvalidRef);
     reg.register_late_lint_pass(box identity_conversion::IdentityConversion::default());
     reg.register_late_lint_pass(box types::ImplicitHasher);
@@ -477,6 +479,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
         identity_op::IDENTITY_OP,
         if_let_redundant_pattern_matching::IF_LET_REDUNDANT_PATTERN_MATCHING,
         infinite_iter::INFINITE_ITER,
+        inline_fn_without_body::INLINE_FN_WITHOUT_BODY,
         invalid_ref::INVALID_REF,
         is_unit_expr::UNIT_EXPR,
         large_enum_variant::LARGE_ENUM_VARIANT,

clippy_lints/src/utils/sugg.rs

@@ -15,6 +15,7 @@ use syntax::print::pprust::token_to_string;
 use syntax::util::parser::AssocOp;
 use syntax::ast;
 use utils::{higher, snippet, snippet_opt};
+use syntax_pos::{BytePos, Pos};
 
 /// A helper type to build suggestion correctly handling parenthesis.
 pub enum Sugg<'a> {
@@ -454,6 +455,19 @@ pub trait DiagnosticBuilderExt<'a, T: LintContext<'a>> {
     /// }");
     /// ```
     fn suggest_prepend_item(&mut self, cx: &T, item: Span, msg: &str, new_item: &str);
+
+    /// Suggest to completely remove an item.
+    ///
+    /// This will remove an item and all following whitespace until the next non-whitespace
+    /// character. This should work correctly if item is on the same indentation level as the
+    /// following item.
+    ///
+    /// # Example
+    ///
+    /// ```rust,ignore
+    /// db.suggest_remove_item(cx, item, "remove this")
+    /// ```
+    fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str);
 }
 
 impl<'a, 'b, 'c, T: LintContext<'c>> DiagnosticBuilderExt<'c, T> for rustc_errors::DiagnosticBuilder<'b> {
@@ -485,4 +499,21 @@ impl<'a, 'b, 'c, T: LintContext<'c>> DiagnosticBuilderExt<'c, T> for rustc_error
             self.span_suggestion(span, msg, format!("{}\n{}", new_item, indent));
         }
     }
+
+    fn suggest_remove_item(&mut self, cx: &T, item: Span, msg: &str) {
+        let mut remove_span = item;
+        let fmpos = cx.sess()
+            .codemap()
+            .lookup_byte_offset(remove_span.next_point().hi());
+
+        if let Some(ref src) = fmpos.fm.src {
+            let non_whitespace_offset = src[fmpos.pos.to_usize()..].find(|c| c != ' ' && c != '\t' && c != '\n');
+
+            if let Some(non_whitespace_offset) = non_whitespace_offset {
+                remove_span = remove_span.with_hi(remove_span.hi() + BytePos(non_whitespace_offset as u32))
+            }
+        }
+
+        self.span_suggestion(remove_span, msg, String::new());
+    }
 }

tests/ui/inline_fn_without_body.rs

@@ -0,0 +1,23 @@
+
+
+
+#![warn(inline_fn_without_body)]
+#![allow(inline_always)]
+
+trait Foo {
+    #[inline]
+    fn default_inline();
+
+    #[inline(always)]fn always_inline();
+
+    #[inline(never)]
+
+    fn never_inline();
+
+    #[inline]
+    fn has_body() {
+    }
+}
+
+fn main() {
+}

tests/ui/inline_fn_without_body.stderr

@@ -0,0 +1,27 @@
+error: use of `#[inline]` on trait method `default_inline` which has no body
+ --> $DIR/inline_fn_without_body.rs:8:5
+  |
+8 |       #[inline]
+  |  _____-^^^^^^^^
+9 | |     fn default_inline();
+  | |____- help: remove
+  |
+  = note: `-D inline-fn-without-body` implied by `-D warnings`
+
+error: use of `#[inline]` on trait method `always_inline` which has no body
+  --> $DIR/inline_fn_without_body.rs:11:5
+   |
+11 |     #[inline(always)]fn always_inline();
+   |     ^^^^^^^^^^^^^^^^^ help: remove
+
+error: use of `#[inline]` on trait method `never_inline` which has no body
+  --> $DIR/inline_fn_without_body.rs:13:5
+   |
+13 |       #[inline(never)]
+   |  _____-^^^^^^^^^^^^^^^
+14 | |
+15 | |     fn never_inline();
+   | |____- help: remove
+
+error: aborting due to 3 previous errors
+