Implementation of the const_static_lifetime lint.

Author: gbip

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;
@@ -337,6 +338,7 @@ 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,
@@ -347,6 +349,7 @@ 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,

tests/ui/const_static_lifetime.rs

@@ -0,0 +1,33 @@
+#![feature(plugin)]
+
+#[derive(Debug)]
+struct Foo {}
+
+const VAR_ONE: &'static str = "Test constant #1"; // ERROR Consider removing 'static.
+
+const VAR_TWO: &str = "Test constant #2"; // This line should not raise a warning.
+
+const VAR_THREE: &[&'static str] = &["one", "two"]; // ERROR Consider removing 'static
+
+const VAR_FOUR: (&str, (&str, &'static str), &'static str) = ("on", ("th", "th"), "on"); // ERROR Consider removing 'static
+
+const VAR_FIVE: &'static [&[&'static str]] = &[&["test"], &["other one"]]; // ERROR Consider removing 'static
+
+const VAR_SIX: &'static u8 = &5;
+
+const VAR_SEVEN: &[&(&str, &'static [&'static str])] = &[&("one", &["other one"])];
+
+const VAR_HEIGHT: &'static Foo = &Foo {};
+
+fn main() {
+    let false_positive: &'static str = "test";
+    println!("{}", VAR_ONE);
+    println!("{}", VAR_TWO);
+    println!("{:?}", VAR_THREE);
+    println!("{:?}", VAR_FOUR);
+    println!("{:?}", VAR_FIVE);
+    println!("{:?}", VAR_SIX);
+    println!("{:?}", VAR_SEVEN);
+    println!("{:?}", VAR_HEIGHT);
+    println!("{}", false_positive);
+}

tests/ui/regex.rs

@@ -9,8 +9,8 @@ extern crate regex;
 use regex::{Regex, RegexSet, RegexBuilder};
 use regex::bytes::{Regex as BRegex, RegexSet as BRegexSet, RegexBuilder as BRegexBuilder};
 
-const OPENING_PAREN : &'static str = "(";
-const NOT_A_REAL_REGEX : &'static str = "foobar";
+const OPENING_PAREN: &str = "(";
+const NOT_A_REAL_REGEX: &str = "foobar";
 
 fn syntax_error() {
     let pipe_in_wrong_position = Regex::new("|");
@@ -27,23 +27,11 @@ fn syntax_error() {
     let closing_paren = ")";
     let not_linted = Regex::new(closing_paren);
 
-    let set = RegexSet::new(&[
-        r"[a-z]+@[a-z]+\.(com|org|net)",
-        r"[a-z]+\.(com|org|net)",
-    ]);
-    let bset = BRegexSet::new(&[
-        r"[a-z]+@[a-z]+\.(com|org|net)",
-        r"[a-z]+\.(com|org|net)",
-    ]);
-
-    let set_error = RegexSet::new(&[
-        OPENING_PAREN,
-        r"[a-z]+\.(com|org|net)",
-    ]);
-    let bset_error = BRegexSet::new(&[
-        OPENING_PAREN,
-        r"[a-z]+\.(com|org|net)",
-    ]);
+    let set = RegexSet::new(&[r"[a-z]+@[a-z]+\.(com|org|net)", r"[a-z]+\.(com|org|net)"]);
+    let bset = BRegexSet::new(&[r"[a-z]+@[a-z]+\.(com|org|net)", r"[a-z]+\.(com|org|net)"]);
+
+    let set_error = RegexSet::new(&[OPENING_PAREN, r"[a-z]+\.(com|org|net)"]);
+    let bset_error = BRegexSet::new(&[OPENING_PAREN, r"[a-z]+\.(com|org|net)"]);
 }
 
 fn trivial_regex() {