-use crate::utils::{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::{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 syntax_pos::Span;
+use crate::utils::qualify_min_const_fn::is_min_const_fn;
+use crate::utils::{
+ fn_has_unsatisfiable_preds, has_drop, is_entrypoint_fn, meets_msrv, span_lint, trait_ref_of_method,
+};
+use rustc_hir as hir;
+use rustc_hir::intravisit::FnKind;
+use rustc_hir::{Body, Constness, FnDecl, GenericParamKind, HirId};
+use rustc_lint::{LateContext, LateLintPass, LintContext};
+use rustc_middle::lint::in_external_macro;
+use rustc_semver::RustcVersion;
+use rustc_session::{declare_tool_lint, impl_lint_pass};
+use rustc_span::Span;
+use rustc_typeck::hir_ty_to_ty;
+
+const MISSING_CONST_FOR_FN_MSRV: RustcVersion = RustcVersion::new(1, 37, 0);
declare_clippy_lint! {
/// **What it does:**
/// **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`"
}
-declare_lint_pass!(MissingConstForFn => [MISSING_CONST_FOR_FN]);
+impl_lint_pass!(MissingConstForFn => [MISSING_CONST_FOR_FN]);
+
+pub struct MissingConstForFn {
+ msrv: Option<RustcVersion>,
+}
+
+impl MissingConstForFn {
+ #[must_use]
+ pub fn new(msrv: Option<RustcVersion>) -> Self {
+ Self { msrv }
+ }
+}
-impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MissingConstForFn {
+impl<'tcx> LateLintPass<'tcx> for MissingConstForFn {
fn check_fn(
&mut self,
- cx: &LateContext<'_, '_>,
+ cx: &LateContext<'_>,
kind: FnKind<'_>,
- _: &FnDecl,
- _: &Body,
+ _: &FnDecl<'_>,
+ _: &Body<'_>,
span: Span,
hir_id: HirId,
) {
- let def_id = cx.tcx.hir().local_def_id_from_hir_id(hir_id);
+ if !meets_msrv(self.msrv.as_ref(), &MISSING_CONST_FOR_FN_MSRV) {
+ return;
+ }
- if in_external_macro(cx.tcx.sess, span) || is_entrypoint_fn(cx, def_id) {
+ let def_id = cx.tcx.hir().local_def_id(hir_id);
+
+ if in_external_macro(cx.tcx.sess, span) || is_entrypoint_fn(cx, def_id.to_def_id()) {
+ return;
+ }
+
+ // Building MIR for `fn`s with unsatisfiable preds results in ICE.
+ if fn_has_unsatisfiable_preds(cx, def_id.to_def_id()) {
return;
}
// Perform some preliminary checks that rule out constness on the Clippy side. This way we
// can skip the actual const check and return early.
match kind {
- FnKind::ItemFn(_, _, header, ..) => {
- if already_const(header) {
+ FnKind::ItemFn(_, generics, header, ..) => {
+ let has_const_generic_params = generics
+ .params
+ .iter()
+ .any(|param| matches!(param.kind, GenericParamKind::Const { .. }));
+
+ if already_const(header) || has_const_generic_params {
return;
}
},
FnKind::Method(_, sig, ..) => {
- if trait_ref_of_method(cx, hir_id).is_some() || 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;
}
},
- _ => return,
+ FnKind::Closure => return,
}
let mir = cx.tcx.optimized_mir(def_id);
- if let Err((span, err)) = is_min_const_fn(cx.tcx, def_id, &mir) {
- if cx.tcx.is_min_const_fn(def_id) {
+ if let Err((span, err)) = is_min_const_fn(cx.tcx, &mir) {
+ if rustc_mir::const_eval::is_min_const_fn(cx.tcx, def_id.to_def_id()) {
cx.tcx.sess.span_err(span, &err);
}
} else {
- span_lint(cx, MISSING_CONST_FOR_FN, span, "this could be a const_fn");
+ span_lint(cx, MISSING_CONST_FOR_FN, span, "this could be a `const fn`");
}
}
+ extract_msrv_attr!(LateContext);
+}
+
+/// 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: &[hir::Ty<'_>]) -> bool {
+ // If any of the params are droppable, 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`
+#[must_use]
fn already_const(header: hir::FnHeader) -> bool {
header.constness == Constness::Const
}