use clippy_utils::diagnostics::span_lint_and_then;
+use clippy_utils::get_parent_node;
use clippy_utils::source::snippet_with_macro_callsite;
-use clippy_utils::visitors::for_each_value_source;
+use clippy_utils::visitors::{for_each_local_assignment, for_each_value_source};
use core::ops::ControlFlow;
use rustc_errors::Applicability;
use rustc_hir::def::{DefKind, Res};
-use rustc_hir::{Expr, ExprKind, PatKind, Stmt, StmtKind};
+use rustc_hir::{Expr, ExprKind, HirId, HirIdSet, Local, Node, PatKind, QPath, TyKind};
use rustc_lint::{LateContext, LintContext};
use rustc_middle::lint::in_external_macro;
-use rustc_middle::ty::{self, Ty, TypeFoldable, TypeSuperFoldable, TypeVisitor};
+use rustc_middle::ty;
use super::LET_UNIT_VALUE;
-pub(super) fn check(cx: &LateContext<'_>, stmt: &Stmt<'_>) {
- if let StmtKind::Local(local) = stmt.kind
- && let Some(init) = local.init
+pub(super) fn check<'tcx>(cx: &LateContext<'tcx>, local: &'tcx Local<'_>) {
+ if let Some(init) = local.init
&& !local.pat.span.from_expansion()
- && !in_external_macro(cx.sess(), stmt.span)
+ && !in_external_macro(cx.sess(), local.span)
&& cx.typeck_results().pat_ty(local.pat).is_unit()
{
- let needs_inferred = for_each_value_source(init, &mut |e| if needs_inferred_result_ty(cx, e) {
- ControlFlow::Continue(())
- } else {
- ControlFlow::Break(())
- }).is_continue();
-
- if needs_inferred {
- if !matches!(local.pat.kind, PatKind::Wild) {
+ if (local.ty.map_or(false, |ty| !matches!(ty.kind, TyKind::Infer))
+ || matches!(local.pat.kind, PatKind::Tuple([], None)))
+ && expr_needs_inferred_result(cx, init)
+ {
+ if !matches!(local.pat.kind, PatKind::Wild | PatKind::Tuple([], None)) {
span_lint_and_then(
cx,
LET_UNIT_VALUE,
- stmt.span,
+ local.span,
"this let-binding has unit value",
|diag| {
- diag.span_suggestion(
- local.pat.span,
- "use a wild (`_`) binding",
- "_",
- Applicability::MaybeIncorrect, // snippet
- );
+ diag.span_suggestion(
+ local.pat.span,
+ "use a wild (`_`) binding",
+ "_",
+ Applicability::MaybeIncorrect, // snippet
+ );
},
);
}
span_lint_and_then(
cx,
LET_UNIT_VALUE,
- stmt.span,
+ local.span,
"this let-binding has unit value",
|diag| {
if let Some(expr) = &local.init {
let snip = snippet_with_macro_callsite(cx, expr.span, "()");
diag.span_suggestion(
- stmt.span,
+ local.span,
"omit the `let` binding",
- format!("{};", snip),
+ format!("{snip};"),
Applicability::MachineApplicable, // snippet
);
}
}
}
-fn needs_inferred_result_ty(cx: &LateContext<'_>, e: &Expr<'_>) -> bool {
- let id = match e.kind {
+/// Checks sub-expressions which create the value returned by the given expression for whether
+/// return value inference is needed. This checks through locals to see if they also need inference
+/// at this point.
+///
+/// e.g.
+/// ```rust,ignore
+/// let bar = foo();
+/// let x: u32 = if true { baz() } else { bar };
+/// ```
+/// Here the sources of the value assigned to `x` would be `baz()`, and `foo()` via the
+/// initialization of `bar`. If both `foo` and `baz` have a return type which require type
+/// inference then this function would return `true`.
+fn expr_needs_inferred_result<'tcx>(cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) -> bool {
+ // The locals used for initialization which have yet to be checked.
+ let mut locals_to_check = Vec::new();
+ // All the locals which have been added to `locals_to_check`. Needed to prevent cycles.
+ let mut seen_locals = HirIdSet::default();
+ if !each_value_source_needs_inference(cx, e, &mut locals_to_check, &mut seen_locals) {
+ return false;
+ }
+ while let Some(id) = locals_to_check.pop() {
+ if let Some(Node::Local(l)) = get_parent_node(cx.tcx, id) {
+ if !l.ty.map_or(true, |ty| matches!(ty.kind, TyKind::Infer)) {
+ return false;
+ }
+ if let Some(e) = l.init {
+ if !each_value_source_needs_inference(cx, e, &mut locals_to_check, &mut seen_locals) {
+ return false;
+ }
+ } else if for_each_local_assignment(cx, id, |e| {
+ if each_value_source_needs_inference(cx, e, &mut locals_to_check, &mut seen_locals) {
+ ControlFlow::Continue(())
+ } else {
+ ControlFlow::Break(())
+ }
+ })
+ .is_break()
+ {
+ return false;
+ }
+ }
+ }
+
+ true
+}
+
+fn each_value_source_needs_inference(
+ cx: &LateContext<'_>,
+ e: &Expr<'_>,
+ locals_to_check: &mut Vec<HirId>,
+ seen_locals: &mut HirIdSet,
+) -> bool {
+ for_each_value_source(e, &mut |e| {
+ if needs_inferred_result_ty(cx, e, locals_to_check, seen_locals) {
+ ControlFlow::Continue(())
+ } else {
+ ControlFlow::Break(())
+ }
+ })
+ .is_continue()
+}
+
+fn needs_inferred_result_ty(
+ cx: &LateContext<'_>,
+ e: &Expr<'_>,
+ locals_to_check: &mut Vec<HirId>,
+ seen_locals: &mut HirIdSet,
+) -> bool {
+ let (id, args) = match e.kind {
ExprKind::Call(
Expr {
kind: ExprKind::Path(ref path),
hir_id,
..
},
- _,
+ args,
) => match cx.qpath_res(path, *hir_id) {
- Res::Def(DefKind::AssocFn | DefKind::Fn, id) => id,
+ Res::Def(DefKind::AssocFn | DefKind::Fn, id) => (id, args),
_ => return false,
},
- ExprKind::MethodCall(..) => match cx.typeck_results().type_dependent_def_id(e.hir_id) {
- Some(id) => id,
+ ExprKind::MethodCall(_, args, _) => match cx.typeck_results().type_dependent_def_id(e.hir_id) {
+ Some(id) => (id, args),
None => return false,
},
+ ExprKind::Path(QPath::Resolved(None, path)) => {
+ if let Res::Local(id) = path.res
+ && seen_locals.insert(id)
+ {
+ locals_to_check.push(id);
+ }
+ return true;
+ },
_ => return false,
};
let sig = cx.tcx.fn_sig(id).skip_binder();
if let ty::Param(output_ty) = *sig.output().kind() {
- sig.inputs().iter().all(|&ty| !ty_contains_param(ty, output_ty.index))
+ sig.inputs().iter().zip(args).all(|(&ty, arg)| {
+ !ty.is_param(output_ty.index) || each_value_source_needs_inference(cx, arg, locals_to_check, seen_locals)
+ })
} else {
false
}
}
-
-fn ty_contains_param(ty: Ty<'_>, index: u32) -> bool {
- struct Visitor(u32);
- impl<'tcx> TypeVisitor<'tcx> for Visitor {
- type BreakTy = ();
- fn visit_ty(&mut self, ty: Ty<'tcx>) -> ControlFlow<Self::BreakTy> {
- if let ty::Param(ty) = *ty.kind() {
- if ty.index == self.0 {
- ControlFlow::BREAK
- } else {
- ControlFlow::CONTINUE
- }
- } else {
- ty.super_visit_with(self)
- }
- }
- }
- ty.visit_with(&mut Visitor(index)).is_break()
-}
projects / rustc.git / blobdiff