-use rustc::hir;
-use rustc::hir::{Body, FnDecl, Constness};
-use rustc::hir::intravisit::FnKind;
-// use rustc::mir::*;
-use syntax::ast::{NodeId, Attribute};
-use syntax_pos::Span;
-use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
-use rustc::{declare_tool_lint, lint_array};
-use rustc_mir::transform::qualify_min_const_fn::is_min_const_fn;
-use crate::utils::{span_lint, is_entrypoint_fn};
+use clippy_utils::diagnostics::span_lint;
+use clippy_utils::qualify_min_const_fn::is_min_const_fn;
+use clippy_utils::ty::has_drop;
+use clippy_utils::{fn_has_unsatisfiable_preds, is_entrypoint_fn, meets_msrv, msrvs, 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;
-/// **What it does:**
-///
-/// Suggests the use of `const` in functions and methods where possible
-///
-/// **Why is this bad?**
-/// Not using `const` is a missed optimization. Instead of having the function execute at runtime,
-/// when using `const`, it's evaluated at compiletime.
-///
-/// **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_lint_pass!(MissingConstForFn => [MISSING_CONST_FOR_FN]);
-impl LintPass for MissingConstForFn {
- fn get_lints(&self) -> LintArray {
- lint_array!(MISSING_CONST_FOR_FN)
- }
+pub struct MissingConstForFn {
+ msrv: Option<RustcVersion>,
+}
- fn name(&self) -> &'static str {
- "MissingConstForFn"
+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,
- node_id: NodeId
+ hir_id: HirId,
) {
- let def_id = cx.tcx.hir().local_def_id(node_id);
+ if !meets_msrv(self.msrv.as_ref(), &msrvs::CONST_IF_MATCH) {
+ return;
+ }
+
+ 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(_, 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)
+ || method_accepts_dropable(cx, sig.decl.inputs)
+ {
+ return;
+ }
+ },
+ FnKind::Closure => return,
+ }
+
let mir = cx.tcx.optimized_mir(def_id);
- if let Ok(_) = is_min_const_fn(cx.tcx, def_id, &mir) {
- match kind {
- FnKind::ItemFn(name, _generics, header, _vis, attrs) => {
- if !can_be_const_fn(&name.as_str(), header, attrs) {
- return;
- }
- },
- FnKind::Method(ident, sig, _vis, attrs) => {
- let header = sig.header;
- let name = ident.name.as_str();
- if !can_be_const_fn(&name, header, attrs) {
- return;
- }
- },
- _ => return
+
+ if let Err((span, err)) = is_min_const_fn(cx.tcx, mir, self.msrv.as_ref()) {
+ if cx.tcx.is_const_fn_raw(def_id.to_def_id()) {
+ cx.tcx.sess.span_err(span, &err);
}
- span_lint(cx, MISSING_CONST_FOR_FN, span, "this could be a const_fn");
+ } else {
+ span_lint(cx, MISSING_CONST_FOR_FN, span, "this could be a `const fn`");
}
}
+ extract_msrv_attr!(LateContext);
}
-fn can_be_const_fn(name: &str, header: hir::FnHeader, attrs: &[Attribute]) -> bool {
- // Main and custom entrypoints can't be `const`
- if is_entrypoint_fn(name, attrs) { return false }
+/// 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`
- if header.constness == Constness::Const { return false }
- true
+// 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
}
projects / rust.git / blobdiff