Implementation of the const_static_lifetime lint.

clippy_lints/src/const_static_lifetime.rs

@@ -0,0 +1,82 @@
+use syntax::ast::{Item, ItemKind, TyKind, Ty};
+use rustc::lint::{LintPass, EarlyLintPass, LintArray, EarlyContext};
+use utils::{span_help_and_lint, in_macro};
+
+/// **What it does:** Checks for constants with an explicit `'static` lifetime.
+///
+/// **Why is this bad?** Adding `'static` to every reference can create very complicated types.
+///
+/// **Known problems:** None.
+///
+/// **Example:**
+/// ```rust
+///  const FOO: &'static [(&'static str, &'static str, fn(&Bar) -> bool)] = &[..]
+/// ```
+/// This code can be rewritten as
+/// ```rust
+///  const FOO: &[(&str, &str, fn(&Bar) -> bool)] = &[...]
+/// ```
+
+declare_lint! {
+    pub CONST_STATIC_LIFETIME, 
+    Warn,
+    "Using explicit `'static` lifetime for constants when elision rules would allow omitting them."
+}
+
+pub struct StaticConst;
+
+impl LintPass for StaticConst {
+    fn get_lints(&self) -> LintArray {
+        lint_array!(CONST_STATIC_LIFETIME)
+    }
+}
+
+impl StaticConst {
+    // Recursively visit types
+    fn visit_type(&mut self, ty: &Ty, cx: &EarlyContext) {
+        match ty.node {
+            // Be carefull of nested structures (arrays and tuples)
+            TyKind::Array(ref ty, _) => {
+                println!("array");
+                self.visit_type(&*ty, cx);
+            },
+            TyKind::Tup(ref tup) => {
+                for tup_ty in tup {
+                    self.visit_type(&*tup_ty, cx);
+                }
+            },
+            // This is what we are looking for !
+            TyKind::Rptr(ref optional_lifetime, ref borrow_type) => {
+                // Match the 'static lifetime
+                if let Some(lifetime) = *optional_lifetime {
+                    if let TyKind::Path(_, _) = borrow_type.ty.node {
+                        // Verify that the path is a str
+                        if lifetime.ident.name == "'static" {
+                            span_help_and_lint(cx,
+                                               CONST_STATIC_LIFETIME,
+                                               lifetime.span,
+                                               "Constants have by default a `'static` lifetime",
+                                               "consider removing `'static`");
+                        }
+                    }
+                }
+                self.visit_type(&*borrow_type.ty, cx);
+            },
+            TyKind::Slice(ref ty) => {
+                self.visit_type(&ty, cx);
+            },
+            _ => {},
+        }
+    }
+}
+
+impl EarlyLintPass for StaticConst {
+    fn check_item(&mut self, cx: &EarlyContext, item: &Item) {
+        if !in_macro(item.span) {
+            // Match only constants...
+            if let ItemKind::Const(ref var_type, _) = item.node {
+                self.visit_type(var_type, cx);
+            }
+        }
+    }
+}

clippy_lints/src/lib.rs

@@ -76,6 +76,7 @@ pub mod block_in_if_condition;
 pub mod booleans;
 pub mod bytecount;
 pub mod collapsible_if;
+pub mod const_static_lifetime;
 pub mod copies;
 pub mod cyclomatic_complexity;
 pub mod derive;
@@ -339,6 +340,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
     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);
+    reg.register_early_lint_pass(box const_static_lifetime::StaticConst);
 
     reg.register_lint_group("clippy_restrictions", vec![
         arithmetic::FLOAT_ARITHMETIC,
@@ -349,6 +351,7 @@ pub fn register_plugins(reg: &mut rustc_plugin::Registry) {
 
     reg.register_lint_group("clippy_pedantic", vec![
         booleans::NONMINIMAL_BOOL,
+        const_static_lifetime::CONST_STATIC_LIFETIME,
         empty_enum::EMPTY_ENUM,
         enum_glob_use::ENUM_GLOB_USE,
         enum_variants::PUB_ENUM_VARIANT_NAMES,