-use crate::utils::{is_entrypoint_fn, span_lint};
+use crate::utils::{has_drop, is_entrypoint_fn, span_lint, trait_ref_of_method};
use rustc::hir;
use rustc::hir::intravisit::FnKind;
-use rustc::hir::{Body, Constness, FnDecl, HirId};
-use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
-use rustc::{declare_tool_lint, lint_array};
+use rustc::hir::{Body, Constness, FnDecl, HirId, HirVec};
+use rustc::lint::{in_external_macro, LateContext, LateLintPass, LintArray, LintPass};
+use rustc::{declare_lint_pass, declare_tool_lint};
use rustc_mir::transform::qualify_min_const_fn::is_min_const_fn;
+use rustc_typeck::hir_ty_to_ty;
use syntax_pos::Span;
-/// **What it does:**
-///
-/// Suggests the use of `const` in functions and methods where possible.
-///
-/// **Why is this bad?**
-///
-/// Not having the function const prevents callers of the function from being const as well.
-///
-/// **Known problems:**
-///
-/// Const functions are currently still being worked on, with some features only being available
-/// on nightly. This lint does not consider all edge cases currently and the suggestions may be
-/// incorrect if you are using this lint on stable.
-///
-/// Also, the lint only runs one pass over the code. Consider these two non-const functions:
-///
-/// ```rust
-/// fn a() -> i32 {
-/// 0
-/// }
-/// fn b() -> i32 {
-/// a()
-/// }
-/// ```
-///
-/// When running Clippy, the lint will only suggest to make `a` const, because `b` at this time
-/// can't be const as it calls a non-const function. Making `a` const and running Clippy again,
-/// will suggest to make `b` const, too.
-///
-/// **Example:**
-///
-/// ```rust
-/// fn new() -> Self {
-/// Self { random_number: 42 }
-/// }
-/// ```
-///
-/// Could be a const fn:
-///
-/// ```rust
-/// const fn new() -> Self {
-/// Self { random_number: 42 }
-/// }
-/// ```
declare_clippy_lint! {
+ /// **What it does:**
+ ///
+ /// Suggests the use of `const` in functions and methods where possible.
+ ///
+ /// **Why is this bad?**
+ ///
+ /// Not having the function const prevents callers of the function from being const as well.
+ ///
+ /// **Known problems:**
+ ///
+ /// Const functions are currently still being worked on, with some features only being available
+ /// on nightly. This lint does not consider all edge cases currently and the suggestions may be
+ /// incorrect if you are using this lint on stable.
+ ///
+ /// Also, the lint only runs one pass over the code. Consider these two non-const functions:
+ ///
+ /// ```rust
+ /// fn a() -> i32 {
+ /// 0
+ /// }
+ /// fn b() -> i32 {
+ /// a()
+ /// }
+ /// ```
+ ///
+ /// When running Clippy, the lint will only suggest to make `a` const, because `b` at this time
+ /// can't be const as it calls a non-const function. Making `a` const and running Clippy again,
+ /// will suggest to make `b` const, too.
+ ///
+ /// **Example:**
+ ///
+ /// ```rust
+ /// # struct Foo {
+ /// # random_number: usize,
+ /// # }
+ /// # impl Foo {
+ /// fn new() -> Self {
+ /// Self { random_number: 42 }
+ /// }
+ /// # }
+ /// ```
+ ///
+ /// Could be a const fn:
+ ///
+ /// ```rust
+ /// # struct Foo {
+ /// # random_number: usize,
+ /// # }
+ /// # impl Foo {
+ /// const fn new() -> Self {
+ /// Self { random_number: 42 }
+ /// }
+ /// # }
+ /// ```
pub MISSING_CONST_FOR_FN,
nursery,
"Lint functions definitions that could be made `const fn`"
}
-#[derive(Clone)]
-pub struct MissingConstForFn;
-
-impl LintPass for MissingConstForFn {
- fn get_lints(&self) -> LintArray {
- lint_array!(MISSING_CONST_FOR_FN)
- }
-
- fn name(&self) -> &'static str {
- "MissingConstForFn"
- }
-}
+declare_lint_pass!(MissingConstForFn => [MISSING_CONST_FOR_FN]);
impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingConstForFn {
fn check_fn(
span: Span,
hir_id: HirId,
) {
- let def_id = cx.tcx.hir().local_def_id_from_hir_id(hir_id);
+ let def_id = cx.tcx.hir().local_def_id(hir_id);
- if is_entrypoint_fn(cx, def_id) {
+ if in_external_macro(cx.tcx.sess, span) || is_entrypoint_fn(cx, def_id) {
return;
}
}
},
FnKind::Method(_, sig, ..) => {
- if already_const(sig.header) {
+ if trait_ref_of_method(cx, hir_id).is_some()
+ || already_const(sig.header)
+ || method_accepts_dropable(cx, &sig.decl.inputs)
+ {
return;
}
},
}
}
+/// Returns true if any of the method parameters is a type that implements `Drop`. The method
+/// can't be made const then, because `drop` can't be const-evaluated.
+fn method_accepts_dropable(cx: &LateContext<'_, '_>, param_tys: &HirVec<hir::Ty>) -> bool {
+ // If any of the params are dropable, return true
+ param_tys.iter().any(|hir_ty| {
+ let ty_ty = hir_ty_to_ty(cx.tcx, hir_ty);
+ has_drop(cx, ty_ty)
+ })
+}
+
// We don't have to lint on something that's already `const`
fn already_const(header: hir::FnHeader) -> bool {
header.constness == Constness::Const