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Fix manual_map false positives #6801

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merged 4 commits into from
Mar 2, 2021
Merged

Fix manual_map false positives #6801

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ef87e58
Fix `manual_map`: don't lint when partially moved values are used.
Jarcho Feb 26, 2021
09a827a
Revert #6796: Downgrade manual_map to nursery
Jarcho Feb 26, 2021
a3278a1
Fix `manual_map`: do not expand macros in suggestions
Jarcho Feb 28, 2021
2c485e3
Don't move `yield` or inline assembly into closure
Jarcho Mar 1, 2021
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3 changes: 2 additions & 1 deletion clippy_lints/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -1540,6 +1540,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
LintId::of(&loops::WHILE_LET_ON_ITERATOR),
LintId::of(&main_recursion::MAIN_RECURSION),
LintId::of(&manual_async_fn::MANUAL_ASYNC_FN),
LintId::of(&manual_map::MANUAL_MAP),
LintId::of(&manual_non_exhaustive::MANUAL_NON_EXHAUSTIVE),
LintId::of(&manual_strip::MANUAL_STRIP),
LintId::of(&manual_unwrap_or::MANUAL_UNWRAP_OR),
Expand Down Expand Up @@ -1770,6 +1771,7 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
LintId::of(&loops::WHILE_LET_ON_ITERATOR),
LintId::of(&main_recursion::MAIN_RECURSION),
LintId::of(&manual_async_fn::MANUAL_ASYNC_FN),
LintId::of(&manual_map::MANUAL_MAP),
LintId::of(&manual_non_exhaustive::MANUAL_NON_EXHAUSTIVE),
LintId::of(&map_clone::MAP_CLONE),
LintId::of(&matches::INFALLIBLE_DESTRUCTURING_MATCH),
Expand Down Expand Up @@ -2045,7 +2047,6 @@ pub fn register_plugins(store: &mut rustc_lint::LintStore, sess: &Session, conf:
LintId::of(&floating_point_arithmetic::SUBOPTIMAL_FLOPS),
LintId::of(&future_not_send::FUTURE_NOT_SEND),
LintId::of(&let_if_seq::USELESS_LET_IF_SEQ),
LintId::of(&manual_map::MANUAL_MAP),
LintId::of(&missing_const_for_fn::MISSING_CONST_FOR_FN),
LintId::of(&mutable_debug_assertion::DEBUG_ASSERT_WITH_MUT_CALL),
LintId::of(&mutex_atomic::MUTEX_INTEGER),
Expand Down
210 changes: 137 additions & 73 deletions clippy_lints/src/manual_map.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2,24 +2,32 @@ use crate::{
map_unit_fn::OPTION_MAP_UNIT_FN,
matches::MATCH_AS_REF,
utils::{
is_allowed, is_type_diagnostic_item, match_def_path, match_var, paths, peel_hir_expr_refs,
peel_mid_ty_refs_is_mutable, snippet_with_applicability, span_lint_and_sugg,
can_partially_move_ty, is_allowed, is_type_diagnostic_item, match_def_path, match_var, paths,
peel_hir_expr_refs, peel_mid_ty_refs_is_mutable, snippet_with_applicability, snippet_with_context,
span_lint_and_sugg,
},
};
use rustc_ast::util::parser::PREC_POSTFIX;
use rustc_errors::Applicability;
use rustc_hir::{Arm, BindingAnnotation, Block, Expr, ExprKind, Mutability, Pat, PatKind, QPath};
use rustc_hir::{
def::Res,
intravisit::{walk_expr, ErasedMap, NestedVisitorMap, Visitor},
Arm, BindingAnnotation, Block, Expr, ExprKind, Mutability, Pat, PatKind, Path, QPath,
};
use rustc_lint::{LateContext, LateLintPass, LintContext};
use rustc_middle::lint::in_external_macro;
use rustc_session::{declare_lint_pass, declare_tool_lint};
use rustc_span::symbol::{sym, Ident};
use rustc_span::{
symbol::{sym, Ident},
SyntaxContext,
};

declare_clippy_lint! {
/// **What it does:** Checks for usages of `match` which could be implemented using `map`
///
/// **Why is this bad?** Using the `map` method is clearer and more concise.
///
/// **Known problems:** `map` is not capable of representing some control flow which works fine in `match`.
/// **Known problems:** None.
///
/// **Example:**
///
Expand All @@ -34,7 +42,7 @@ declare_clippy_lint! {
/// Some(0).map(|x| x + 1);
/// ```
pub MANUAL_MAP,
nursery,
style,
"reimplementation of `map`"
}

Expand All @@ -52,43 +60,46 @@ impl LateLintPass<'_> for ManualMap {
{
let (scrutinee_ty, ty_ref_count, ty_mutability) =
peel_mid_ty_refs_is_mutable(cx.typeck_results().expr_ty(scrutinee));
if !is_type_diagnostic_item(cx, scrutinee_ty, sym::option_type)
|| !is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(expr), sym::option_type)
if !(is_type_diagnostic_item(cx, scrutinee_ty, sym::option_type)
&& is_type_diagnostic_item(cx, cx.typeck_results().expr_ty(expr), sym::option_type))
{
return;
}

let (some_expr, some_pat, pat_ref_count, is_wild_none) =
match (try_parse_pattern(cx, arm1.pat), try_parse_pattern(cx, arm2.pat)) {
(Some(OptionPat::Wild), Some(OptionPat::Some { pattern, ref_count }))
if is_none_expr(cx, arm1.body) =>
{
(arm2.body, pattern, ref_count, true)
},
(Some(OptionPat::None), Some(OptionPat::Some { pattern, ref_count }))
if is_none_expr(cx, arm1.body) =>
{
(arm2.body, pattern, ref_count, false)
},
(Some(OptionPat::Some { pattern, ref_count }), Some(OptionPat::Wild))
if is_none_expr(cx, arm2.body) =>
{
(arm1.body, pattern, ref_count, true)
},
(Some(OptionPat::Some { pattern, ref_count }), Some(OptionPat::None))
if is_none_expr(cx, arm2.body) =>
{
(arm1.body, pattern, ref_count, false)
},
_ => return,
};
let expr_ctxt = expr.span.ctxt();
let (some_expr, some_pat, pat_ref_count, is_wild_none) = match (
try_parse_pattern(cx, arm1.pat, expr_ctxt),
try_parse_pattern(cx, arm2.pat, expr_ctxt),
) {
(Some(OptionPat::Wild), Some(OptionPat::Some { pattern, ref_count }))
if is_none_expr(cx, arm1.body) =>
{
(arm2.body, pattern, ref_count, true)
},
(Some(OptionPat::None), Some(OptionPat::Some { pattern, ref_count }))
if is_none_expr(cx, arm1.body) =>
{
(arm2.body, pattern, ref_count, false)
},
(Some(OptionPat::Some { pattern, ref_count }), Some(OptionPat::Wild))
if is_none_expr(cx, arm2.body) =>
{
(arm1.body, pattern, ref_count, true)
},
(Some(OptionPat::Some { pattern, ref_count }), Some(OptionPat::None))
if is_none_expr(cx, arm2.body) =>
{
(arm1.body, pattern, ref_count, false)
},
_ => return,
};

// Top level or patterns aren't allowed in closures.
if matches!(some_pat.kind, PatKind::Or(_)) {
return;
}

let some_expr = match get_some_expr(cx, some_expr) {
let some_expr = match get_some_expr(cx, some_expr, expr_ctxt) {
Some(expr) => expr,
None => return,
};
Expand All @@ -99,6 +110,10 @@ impl LateLintPass<'_> for ManualMap {
return;
}

if !can_move_expr_to_closure(cx, some_expr) {
return;
}

// Determine which binding mode to use.
let explicit_ref = some_pat.contains_explicit_ref_binding();
let binding_ref = explicit_ref.or_else(|| (ty_ref_count != pat_ref_count).then(|| ty_mutability));
Expand All @@ -111,47 +126,50 @@ impl LateLintPass<'_> for ManualMap {

let mut app = Applicability::MachineApplicable;

// Remove address-of expressions from the scrutinee. `as_ref` will be called,
// the type is copyable, or the option is being passed by value.
// Remove address-of expressions from the scrutinee. Either `as_ref` will be called, or
// it's being passed by value.
let scrutinee = peel_hir_expr_refs(scrutinee).0;
let scrutinee_str = snippet_with_applicability(cx, scrutinee.span, "_", &mut app);
let scrutinee_str = if expr.precedence().order() < PREC_POSTFIX {
// Parens are needed to chain method calls.
format!("({})", scrutinee_str)
} else {
scrutinee_str.into()
};
let scrutinee_str = snippet_with_context(cx, scrutinee.span, expr_ctxt, "..", &mut app);
let scrutinee_str =
if scrutinee.span.ctxt() == expr.span.ctxt() && scrutinee.precedence().order() < PREC_POSTFIX {
format!("({})", scrutinee_str)
} else {
scrutinee_str.into()
};

let body_str = if let PatKind::Binding(annotation, _, some_binding, None) = some_pat.kind {
if let Some(func) = can_pass_as_func(cx, some_binding, some_expr) {
snippet_with_applicability(cx, func.span, "..", &mut app).into_owned()
} else {
if match_var(some_expr, some_binding.name)
&& !is_allowed(cx, MATCH_AS_REF, expr.hir_id)
&& binding_ref.is_some()
{
return;
}
match can_pass_as_func(cx, some_binding, some_expr) {
Some(func) if func.span.ctxt() == some_expr.span.ctxt() => {
snippet_with_applicability(cx, func.span, "..", &mut app).into_owned()
},
_ => {
if match_var(some_expr, some_binding.name)
&& !is_allowed(cx, MATCH_AS_REF, expr.hir_id)
&& binding_ref.is_some()
{
return;
}

// `ref` and `ref mut` annotations were handled earlier.
let annotation = if matches!(annotation, BindingAnnotation::Mutable) {
"mut "
} else {
""
};
format!(
"|{}{}| {}",
annotation,
some_binding,
snippet_with_applicability(cx, some_expr.span, "..", &mut app)
)
// `ref` and `ref mut` annotations were handled earlier.
let annotation = if matches!(annotation, BindingAnnotation::Mutable) {
"mut "
} else {
""
};
format!(
"|{}{}| {}",
annotation,
some_binding,
snippet_with_context(cx, some_expr.span, expr_ctxt, "..", &mut app)
)
},
}
} else if !is_wild_none && explicit_ref.is_none() {
// TODO: handle explicit reference annotations.
format!(
"|{}| {}",
snippet_with_applicability(cx, some_pat.span, "..", &mut app),
snippet_with_applicability(cx, some_expr.span, "..", &mut app)
snippet_with_context(cx, some_pat.span, expr_ctxt, "..", &mut app),
snippet_with_context(cx, some_expr.span, expr_ctxt, "..", &mut app)
)
} else {
// Refutable bindings and mixed reference annotations can't be handled by `map`.
Expand All @@ -171,6 +189,51 @@ impl LateLintPass<'_> for ManualMap {
}
}

// Checks if the expression can be moved into a closure as is.
fn can_move_expr_to_closure(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> bool {
struct V<'cx, 'tcx> {
cx: &'cx LateContext<'tcx>,
make_closure: bool,
}
impl Visitor<'tcx> for V<'_, 'tcx> {
type Map = ErasedMap<'tcx>;
fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
NestedVisitorMap::None
}

fn visit_expr(&mut self, e: &'tcx Expr<'_>) {
match e.kind {
ExprKind::Break(..)
| ExprKind::Continue(_)
| ExprKind::Ret(_)
| ExprKind::Yield(..)
| ExprKind::InlineAsm(_)
| ExprKind::LlvmInlineAsm(_) => {
self.make_closure = false;
},
// Accessing a field of a local value can only be done if the type isn't
// partially moved.
ExprKind::Field(base_expr, _)
if matches!(
base_expr.kind,
ExprKind::Path(QPath::Resolved(_, Path { res: Res::Local(_), .. }))
) && can_partially_move_ty(self.cx, self.cx.typeck_results().expr_ty(base_expr)) =>
{
// TODO: check if the local has been partially moved. Assume it has for now.
self.make_closure = false;
return;
}
_ => (),
};
walk_expr(self, e);
}
}

let mut v = V { cx, make_closure: true };
v.visit_expr(expr);
v.make_closure
}

// Checks whether the expression could be passed as a function, or whether a closure is needed.
// Returns the function to be passed to `map` if it exists.
fn can_pass_as_func(cx: &LateContext<'tcx>, binding: Ident, expr: &'tcx Expr<'_>) -> Option<&'tcx Expr<'tcx>> {
Expand Down Expand Up @@ -198,11 +261,11 @@ enum OptionPat<'a> {

// Try to parse into a recognized `Option` pattern.
// i.e. `_`, `None`, `Some(..)`, or a reference to any of those.
fn try_parse_pattern(cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>) -> Option<OptionPat<'tcx>> {
fn f(cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>, ref_count: usize) -> Option<OptionPat<'tcx>> {
fn try_parse_pattern(cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>, ctxt: SyntaxContext) -> Option<OptionPat<'tcx>> {
fn f(cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>, ref_count: usize, ctxt: SyntaxContext) -> Option<OptionPat<'tcx>> {
match pat.kind {
PatKind::Wild => Some(OptionPat::Wild),
PatKind::Ref(pat, _) => f(cx, pat, ref_count + 1),
PatKind::Ref(pat, _) => f(cx, pat, ref_count + 1, ctxt),
PatKind::Path(QPath::Resolved(None, path))
if path
.res
Expand All @@ -215,18 +278,19 @@ fn try_parse_pattern(cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>) -> Option<Optio
if path
.res
.opt_def_id()
.map_or(false, |id| match_def_path(cx, id, &paths::OPTION_SOME)) =>
.map_or(false, |id| match_def_path(cx, id, &paths::OPTION_SOME))
&& pat.span.ctxt() == ctxt =>
{
Some(OptionPat::Some { pattern, ref_count })
},
_ => None,
}
}
f(cx, pat, 0)
f(cx, pat, 0, ctxt)
}

// Checks for an expression wrapped by the `Some` constructor. Returns the contained expression.
fn get_some_expr(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<&'tcx Expr<'tcx>> {
fn get_some_expr(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>, ctxt: SyntaxContext) -> Option<&'tcx Expr<'tcx>> {
// TODO: Allow more complex expressions.
match expr.kind {
ExprKind::Call(
Expand All @@ -235,7 +299,7 @@ fn get_some_expr(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<&'tcx E
..
},
[arg],
) => {
) if ctxt == expr.span.ctxt() => {
if match_def_path(cx, path.res.opt_def_id()?, &paths::OPTION_SOME) {
Some(arg)
} else {
Expand All @@ -249,7 +313,7 @@ fn get_some_expr(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) -> Option<&'tcx E
..
},
_,
) => get_some_expr(cx, expr),
) => get_some_expr(cx, expr, ctxt),
_ => None,
}
}
Expand Down
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