Update upstream source from tag 'upstream/1.52.1+dfsg1'

[rustc.git] / src / tools / clippy / clippy_lints / src / redundant_static_lifetimes.rs

diff --git a/src/tools/clippy/clippy_lints/src/redundant_static_lifetimes.rs b/src/tools/clippy/clippy_lints/src/redundant_static_lifetimes.rs
new file mode 100644 (file)
index 0000000..fcfa3c1
--- /dev/null
+++ b/src/tools/clippy/clippy_lints/src/redundant_static_lifetimes.rs
@@ -0,0 +1,119 @@
+use crate::utils::{meets_msrv, snippet, span_lint_and_then};
+use rustc_ast::ast::{Item, ItemKind, Ty, TyKind};
+use rustc_errors::Applicability;
+use rustc_lint::{EarlyContext, EarlyLintPass};
+use rustc_semver::RustcVersion;
+use rustc_session::{declare_tool_lint, impl_lint_pass};
+
+const REDUNDANT_STATIC_LIFETIMES_MSRV: RustcVersion = RustcVersion::new(1, 17, 0);
+
+declare_clippy_lint! {
+    /// **What it does:** Checks for constants and statics with an explicit `'static` lifetime.
+    ///
+    /// **Why is this bad?** Adding `'static` to every reference can create very
+    /// complicated types.
+    ///
+    /// **Known problems:** None.
+    ///
+    /// **Example:**
+    /// ```ignore
+    /// const FOO: &'static [(&'static str, &'static str, fn(&Bar) -> bool)] =
+    /// &[...]
+    /// static FOO: &'static [(&'static str, &'static str, fn(&Bar) -> bool)] =
+    /// &[...]
+    /// ```
+    /// This code can be rewritten as
+    /// ```ignore
+    ///  const FOO: &[(&str, &str, fn(&Bar) -> bool)] = &[...]
+    ///  static FOO: &[(&str, &str, fn(&Bar) -> bool)] = &[...]
+    /// ```
+    pub REDUNDANT_STATIC_LIFETIMES,
+    style,
+    "Using explicit `'static` lifetime for constants or statics when elision rules would allow omitting them."
+}
+
+pub struct RedundantStaticLifetimes {
+    msrv: Option<RustcVersion>,
+}
+
+impl RedundantStaticLifetimes {
+    #[must_use]
+    pub fn new(msrv: Option<RustcVersion>) -> Self {
+        Self { msrv }
+    }
+}
+
+impl_lint_pass!(RedundantStaticLifetimes => [REDUNDANT_STATIC_LIFETIMES]);
+
+impl RedundantStaticLifetimes {
+    // Recursively visit types
+    fn visit_type(&mut self, ty: &Ty, cx: &EarlyContext<'_>, reason: &str) {
+        match ty.kind {
+            // Be careful of nested structures (arrays and tuples)
+            TyKind::Array(ref ty, _) => {
+                self.visit_type(&*ty, cx, reason);
+            },
+            TyKind::Tup(ref tup) => {
+                for tup_ty in tup {
+                    self.visit_type(&*tup_ty, cx, reason);
+                }
+            },
+            // 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 {
+                    match borrow_type.ty.kind {
+                        TyKind::Path(..) | TyKind::Slice(..) | TyKind::Array(..) | TyKind::Tup(..) => {
+                            if lifetime.ident.name == rustc_span::symbol::kw::StaticLifetime {
+                                let snip = snippet(cx, borrow_type.ty.span, "<type>");
+                                let sugg = format!("&{}", snip);
+                                span_lint_and_then(
+                                    cx,
+                                    REDUNDANT_STATIC_LIFETIMES,
+                                    lifetime.ident.span,
+                                    reason,
+                                    |diag| {
+                                        diag.span_suggestion(
+                                            ty.span,
+                                            "consider removing `'static`",
+                                            sugg,
+                                            Applicability::MachineApplicable, //snippet
+                                        );
+                                    },
+                                );
+                            }
+                        },
+                        _ => {},
+                    }
+                }
+                self.visit_type(&*borrow_type.ty, cx, reason);
+            },
+            TyKind::Slice(ref ty) => {
+                self.visit_type(ty, cx, reason);
+            },
+            _ => {},
+        }
+    }
+}
+
+impl EarlyLintPass for RedundantStaticLifetimes {
+    fn check_item(&mut self, cx: &EarlyContext<'_>, item: &Item) {
+        if !meets_msrv(self.msrv.as_ref(), &REDUNDANT_STATIC_LIFETIMES_MSRV) {
+            return;
+        }
+
+        if !item.span.from_expansion() {
+            if let ItemKind::Const(_, ref var_type, _) = item.kind {
+                self.visit_type(var_type, cx, "constants have by default a `'static` lifetime");
+                // Don't check associated consts because `'static` cannot be elided on those (issue
+                // #2438)
+            }
+
+            if let ItemKind::Static(ref var_type, _, _) = item.kind {
+                self.visit_type(var_type, cx, "statics have by default a `'static` lifetime");
+            }
+        }
+    }
+
+    extract_msrv_attr!(EarlyContext);
+}