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add unused_braces, lint anon_const

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This commit is contained in:
Bastian Kauschke 2020-03-27 21:54:52 +01:00
parent e0a08351a2
commit b3d744c9f5
2 changed files with 407 additions and 170 deletions
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2
src/librustc_lint/lib.rs
View file

@ -104,6 +104,7 @@ macro_rules! early_lint_passes {
$args,
[
UnusedParens: UnusedParens,
UnusedBraces: UnusedBraces,
UnusedImportBraces: UnusedImportBraces,
UnsafeCode: UnsafeCode,
AnonymousParameters: AnonymousParameters,
@ -275,6 +276,7 @@ fn register_builtins(store: &mut LintStore, no_interleave_lints: bool) {
UNUSED_FEATURES,
UNUSED_LABELS,
UNUSED_PARENS,
UNUSED_BRACES,
REDUNDANT_SEMICOLONS
);

575
src/librustc_lint/unused.rs
View file

@ -1,7 +1,9 @@
use crate::Lint;
use crate::{EarlyContext, EarlyLintPass, LateContext, LateLintPass, LintContext};
use rustc::ty::adjustment;
use rustc::ty::{self, Ty};
use rustc_ast::ast;
use rustc_ast::ast::{ExprKind, StmtKind};
use rustc_ast::attr;
use rustc_ast::util::parser;
use rustc_ast_pretty::pprust;
@ -318,16 +320,58 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for UnusedAttributes {
}
}
declare_lint! {
pub(super) UNUSED_PARENS,
Warn,
"`if`, `match`, `while` and `return` do not need parentheses"
#[derive(Copy, Clone, Debug, PartialEq, Eq)]
enum UnusedDelimsCtx {
FunctionArg,
MethodArg,
AssignedValue,
IfCond,
WhileCond,
ForHeadExpr,
MatchHeadExpr,
ReturnValue,
BlockRetValue,
LetHeadExpr,
ArrayLenExpr,
AnonConst,
}
declare_lint_pass!(UnusedParens => [UNUSED_PARENS]);
impl From<UnusedDelimsCtx> for &'static str {
fn from(ctx: UnusedDelimsCtx) -> &'static str {
match ctx {
UnusedDelimsCtx::FunctionArg => "function argument",
UnusedDelimsCtx::MethodArg => "method argument",
UnusedDelimsCtx::AssignedValue => "assigned value",
UnusedDelimsCtx::IfCond => "`if` condition",
UnusedDelimsCtx::WhileCond => "`while` condition",
UnusedDelimsCtx::ForHeadExpr => "`for` head expression",
UnusedDelimsCtx::MatchHeadExpr => "`match` head expression",
UnusedDelimsCtx::ReturnValue => "`return` value",
UnusedDelimsCtx::BlockRetValue => "block return value",
UnusedDelimsCtx::LetHeadExpr => "`let` head expression",
UnusedDelimsCtx::ArrayLenExpr | UnusedDelimsCtx::AnonConst => "const expression",
}
}
}
impl UnusedParens {
fn is_expr_parens_necessary(inner: &ast::Expr, followed_by_block: bool) -> bool {
/// Used by both `UnusedParens` and `UnusedBraces` to prevent code duplication.
trait UnusedDelimLint {
const DELIM_STR: &'static str;
// this cannot be a constant is it refers to a static.
fn lint(&self) -> &'static Lint;
fn check_unused_delims_expr(
&self,
cx: &EarlyContext<'_>,
value: &ast::Expr,
ctx: UnusedDelimsCtx,
followed_by_block: bool,
left_pos: Option<BytePos>,
right_pos: Option<BytePos>,
);
fn is_expr_delims_necessary(inner: &ast::Expr, followed_by_block: bool) -> bool {
followed_by_block
&& match inner.kind {
ast::ExprKind::Ret(_) | ast::ExprKind::Break(..) => true,
@ -335,42 +379,161 @@ impl UnusedParens {
}
}
fn check_unused_parens_expr(
fn emit_unused_delims_expr(
&self,
cx: &EarlyContext<'_>,
value: &ast::Expr,
msg: &str,
followed_by_block: bool,
ctx: UnusedDelimsCtx,
left_pos: Option<BytePos>,
right_pos: Option<BytePos>,
) {
match value.kind {
ast::ExprKind::Paren(ref inner) => {
if !Self::is_expr_parens_necessary(inner, followed_by_block)
&& value.attrs.is_empty()
&& !value.span.from_expansion()
{
let expr_text =
if let Ok(snippet) = cx.sess().source_map().span_to_snippet(value.span) {
snippet
} else {
pprust::expr_to_string(value)
};
let keep_space = (
left_pos.map(|s| s >= value.span.lo()).unwrap_or(false),
right_pos.map(|s| s <= value.span.hi()).unwrap_or(false),
let expr_text = if let Ok(snippet) = cx.sess().source_map().span_to_snippet(value.span) {
snippet
} else {
pprust::expr_to_string(value)
};
let keep_space = (
left_pos.map(|s| s >= value.span.lo()).unwrap_or(false),
right_pos.map(|s| s <= value.span.hi()).unwrap_or(false),
);
self.emit_unused_delims(cx, value.span, &expr_text, ctx.into(), keep_space);
}
/// emits a lint
fn emit_unused_delims(
&self,
cx: &EarlyContext<'_>,
span: Span,
pattern: &str,
msg: &str,
keep_space: (bool, bool),
) {
cx.struct_span_lint(self.lint(), span, |lint| {
let span_msg = format!("unnecessary {} around {}", Self::DELIM_STR, msg);
let mut err = lint.build(&span_msg);
let mut ate_left_paren = false;
let mut ate_right_paren = false;
let parens_removed = pattern.trim_matches(|c| match c {
'(' | '{' => {
if ate_left_paren {
false
} else {
ate_left_paren = true;
true
}
}
')' | '}' => {
if ate_right_paren {
false
} else {
ate_right_paren = true;
true
}
}
_ => false,
});
let replace = {
let mut replace = if keep_space.0 {
let mut s = String::from(" ");
s.push_str(parens_removed);
s
} else {
String::from(parens_removed)
};
if keep_space.1 {
replace.push(' ');
}
replace
};
let suggestion = format!("remove these {}", Self::DELIM_STR);
err.span_suggestion_short(span, &suggestion, replace, Applicability::MachineApplicable);
err.emit();
});
}
fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
use rustc_ast::ast::ExprKind::*;
let (value, ctx, followed_by_block, left_pos, right_pos) = match e.kind {
If(ref cond, ref block, ..) => {
let left = e.span.lo() + rustc_span::BytePos(2);
let right = block.span.lo();
(cond, UnusedDelimsCtx::IfCond, true, Some(left), Some(right))
}
While(ref cond, ref block, ..) => {
let left = e.span.lo() + rustc_span::BytePos(5);
let right = block.span.lo();
(cond, UnusedDelimsCtx::WhileCond, true, Some(left), Some(right))
}
ForLoop(_, ref cond, ref block, ..) => {
(cond, UnusedDelimsCtx::ForHeadExpr, true, None, Some(block.span.lo()))
}
Match(ref head, _) => {
let left = e.span.lo() + rustc_span::BytePos(5);
(head, UnusedDelimsCtx::MatchHeadExpr, true, Some(left), None)
}
Ret(Some(ref value)) => {
let left = e.span.lo() + rustc_span::BytePos(3);
(value, UnusedDelimsCtx::ReturnValue, false, Some(left), None)
}
Assign(_, ref value, _) | AssignOp(.., ref value) => {
(value, UnusedDelimsCtx::AssignedValue, false, None, None)
}
// either function/method call, or something this lint doesn't care about
ref call_or_other => {
let (args_to_check, ctx) = match *call_or_other {
Call(_, ref args) => (&args[..], UnusedDelimsCtx::FunctionArg),
// first "argument" is self (which sometimes needs delims)
MethodCall(_, ref args) => (&args[1..], UnusedDelimsCtx::MethodArg),
// actual catch-all arm
_ => {
return;
}
};
// Don't lint if this is a nested macro expansion: otherwise, the lint could
// trigger in situations that macro authors shouldn't have to care about, e.g.,
// when a parenthesized token tree matched in one macro expansion is matched as
// an expression in another and used as a fn/method argument (Issue #47775)
if e.span.ctxt().outer_expn_data().call_site.from_expansion() {
return;
}
for arg in args_to_check {
self.check_unused_delims_expr(cx, arg, ctx, false, None, None);
}
return;
}
};
self.check_unused_delims_expr(cx, &value, ctx, followed_by_block, left_pos, right_pos);
}
fn check_stmt(&mut self, cx: &EarlyContext<'_>, s: &ast::Stmt) {
match s.kind {
StmtKind::Local(ref local) => {
if let Some(ref value) = local.init {
self.check_unused_delims_expr(
cx,
&value,
UnusedDelimsCtx::AssignedValue,
false,
None,
None,
);
Self::remove_outer_parens(cx, value.span, &expr_text, msg, keep_space);
}
}
ast::ExprKind::Let(_, ref expr) => {
// FIXME(#60336): Properly handle `let true = (false && true)`
// actually needing the parenthesis.
self.check_unused_parens_expr(
StmtKind::Expr(ref expr) => {
self.check_unused_delims_expr(
cx,
expr,
"`let` head expression",
followed_by_block,
&expr,
UnusedDelimsCtx::BlockRetValue,
false,
None,
None,
);
@ -379,6 +542,73 @@ impl UnusedParens {
}
}
fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
use ast::ItemKind::*;
if let Const(.., Some(expr)) | Static(.., Some(expr)) = &item.kind {
self.check_unused_delims_expr(
cx,
expr,
UnusedDelimsCtx::AssignedValue,
false,
None,
None,
);
}
}
}
declare_lint! {
pub(super) UNUSED_PARENS,
Warn,
"`if`, `match`, `while` and `return` do not need parentheses"
}
declare_lint_pass!(UnusedParens => [UNUSED_PARENS]);
impl UnusedDelimLint for UnusedParens {
const DELIM_STR: &'static str = "parentheses";
fn lint(&self) -> &'static Lint {
UNUSED_PARENS
}
fn check_unused_delims_expr(
&self,
cx: &EarlyContext<'_>,
value: &ast::Expr,
ctx: UnusedDelimsCtx,
followed_by_block: bool,
left_pos: Option<BytePos>,
right_pos: Option<BytePos>,
) {
match value.kind {
ast::ExprKind::Paren(ref inner) => {
if !Self::is_expr_delims_necessary(inner, followed_by_block)
&& value.attrs.is_empty()
&& !value.span.from_expansion()
{
self.emit_unused_delims_expr(cx, value, ctx, left_pos, right_pos)
}
}
ast::ExprKind::Let(_, ref expr) => {
// FIXME(#60336): Properly handle `let true = (false && true)`
// actually needing the parenthesis.
self.check_unused_delims_expr(
cx,
expr,
UnusedDelimsCtx::LetHeadExpr,
followed_by_block,
None,
None,
);
}
_ => {}
}
}
}
impl UnusedParens {
fn check_unused_parens_pat(
&self,
cx: &EarlyContext<'_>,
@ -409,132 +639,18 @@ impl UnusedParens {
} else {
pprust::pat_to_string(value)
};
Self::remove_outer_parens(cx, value.span, &pattern_text, "pattern", (false, false));
self.emit_unused_delims(cx, value.span, &pattern_text, "pattern", (false, false));
}
}
fn remove_outer_parens(
cx: &EarlyContext<'_>,
span: Span,
pattern: &str,
msg: &str,
keep_space: (bool, bool),
) {
cx.struct_span_lint(UNUSED_PARENS, span, |lint| {
let span_msg = format!("unnecessary parentheses around {}", msg);
let mut err = lint.build(&span_msg);
let mut ate_left_paren = false;
let mut ate_right_paren = false;
let parens_removed = pattern.trim_matches(|c| match c {
'(' => {
if ate_left_paren {
false
} else {
ate_left_paren = true;
true
}
}
')' => {
if ate_right_paren {
false
} else {
ate_right_paren = true;
true
}
}
_ => false,
});
let replace = {
let mut replace = if keep_space.0 {
let mut s = String::from(" ");
s.push_str(parens_removed);
s
} else {
String::from(parens_removed)
};
if keep_space.1 {
replace.push(' ');
}
replace
};
err.span_suggestion_short(
span,
"remove these parentheses",
replace,
Applicability::MachineApplicable,
);
err.emit();
});
}
}
impl EarlyLintPass for UnusedParens {
fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
use rustc_ast::ast::ExprKind::*;
let (value, msg, followed_by_block, left_pos, right_pos) = match e.kind {
Let(ref pat, ..) => {
self.check_unused_parens_pat(cx, pat, false, false);
return;
}
if let ExprKind::Let(ref pat, ..) | ExprKind::ForLoop(ref pat, ..) = e.kind {
self.check_unused_parens_pat(cx, pat, false, false);
}
If(ref cond, ref block, ..) => {
let left = e.span.lo() + rustc_span::BytePos(2);
let right = block.span.lo();
(cond, "`if` condition", true, Some(left), Some(right))
}
While(ref cond, ref block, ..) => {
let left = e.span.lo() + rustc_span::BytePos(5);
let right = block.span.lo();
(cond, "`while` condition", true, Some(left), Some(right))
}
ForLoop(ref pat, ref cond, ref block, ..) => {
self.check_unused_parens_pat(cx, pat, false, false);
(cond, "`for` head expression", true, None, Some(block.span.lo()))
}
Match(ref head, _) => {
let left = e.span.lo() + rustc_span::BytePos(5);
(head, "`match` head expression", true, Some(left), None)
}
Ret(Some(ref value)) => {
let left = e.span.lo() + rustc_span::BytePos(3);
(value, "`return` value", false, Some(left), None)
}
Assign(_, ref value, _) => (value, "assigned value", false, None, None),
AssignOp(.., ref value) => (value, "assigned value", false, None, None),
// either function/method call, or something this lint doesn't care about
ref call_or_other => {
let (args_to_check, call_kind) = match *call_or_other {
Call(_, ref args) => (&args[..], "function"),
// first "argument" is self (which sometimes needs parens)
MethodCall(_, ref args) => (&args[1..], "method"),
// actual catch-all arm
_ => {
return;
}
};
// Don't lint if this is a nested macro expansion: otherwise, the lint could
// trigger in situations that macro authors shouldn't have to care about, e.g.,
// when a parenthesized token tree matched in one macro expansion is matched as
// an expression in another and used as a fn/method argument (Issue #47775)
if e.span.ctxt().outer_expn_data().call_site.from_expansion() {
return;
}
let msg = format!("{} argument", call_kind);
for arg in args_to_check {
self.check_unused_parens_expr(cx, arg, &msg, false, None, None);
}
return;
}
};
self.check_unused_parens_expr(cx, &value, msg, followed_by_block, left_pos, right_pos);
<Self as UnusedDelimLint>::check_expr(self, cx, e)
}
fn check_pat(&mut self, cx: &EarlyContext<'_>, p: &ast::Pat) {
@ -559,22 +675,16 @@ impl EarlyLintPass for UnusedParens {
}
}
fn check_anon_const(&mut self, cx: &EarlyContext<'_>, c: &ast::AnonConst) {
self.check_unused_delims_expr(cx, &c.value, UnusedDelimsCtx::AnonConst, false, None, None);
}
fn check_stmt(&mut self, cx: &EarlyContext<'_>, s: &ast::Stmt) {
use ast::StmtKind::*;
match s.kind {
Local(ref local) => {
self.check_unused_parens_pat(cx, &local.pat, false, false);
if let Some(ref value) = local.init {
self.check_unused_parens_expr(cx, &value, "assigned value", false, None, None);
}
}
Expr(ref expr) => {
self.check_unused_parens_expr(cx, &expr, "block return value", false, None, None);
}
_ => {}
if let StmtKind::Local(ref local) = s.kind {
self.check_unused_parens_pat(cx, &local.pat, false, false);
}
<Self as UnusedDelimLint>::check_stmt(self, cx, s)
}
fn check_param(&mut self, cx: &EarlyContext<'_>, param: &ast::Param) {
@ -590,6 +700,16 @@ impl EarlyLintPass for UnusedParens {
match &r.kind {
&ast::TyKind::TraitObject(..) => {}
&ast::TyKind::ImplTrait(_, ref bounds) if bounds.len() > 1 => {}
&ast::TyKind::Array(_, ref len) => {
self.check_unused_delims_expr(
cx,
&len.value,
UnusedDelimsCtx::ArrayLenExpr,
false,
None,
None,
);
}
_ => {
let pattern_text =
if let Ok(snippet) = cx.sess().source_map().span_to_snippet(ty.span) {
@ -598,21 +718,136 @@ impl EarlyLintPass for UnusedParens {
pprust::ty_to_string(ty)
};
Self::remove_outer_parens(cx, ty.span, &pattern_text, "type", (false, false));
self.emit_unused_delims(cx, ty.span, &pattern_text, "type", (false, false));
}
}
}
}
fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
use ast::ItemKind::*;
<Self as UnusedDelimLint>::check_item(self, cx, item)
}
}
if let Const(.., Some(expr)) | Static(.., Some(expr)) = &item.kind {
self.check_unused_parens_expr(cx, expr, "assigned value", false, None, None);
declare_lint! {
pub(super) UNUSED_BRACES,
Warn,
"suggests removing `{` and `}` in case they are not necessary"
}
declare_lint_pass!(UnusedBraces => [UNUSED_BRACES]);
impl UnusedDelimLint for UnusedBraces {
const DELIM_STR: &'static str = "braces";
fn lint(&self) -> &'static Lint {
UNUSED_BRACES
}
fn check_unused_delims_expr(
&self,
cx: &EarlyContext<'_>,
value: &ast::Expr,
ctx: UnusedDelimsCtx,
followed_by_block: bool,
left_pos: Option<BytePos>,
right_pos: Option<BytePos>,
) {
match value.kind {
ast::ExprKind::Block(ref inner, None)
if inner.rules == ast::BlockCheckMode::Default =>
{
// emit a warning under the following conditions:
//
// - the block does not have a label
// - the block is not `unsafe`
// - the block contains exactly one expression (do not lint `{ expr; }`)
// - `followed_by_block` is true and the internal expr may contain a `{`
// - the block is not multiline (do not lint multiline match arms)
// ```
// match expr {
// Pattern => {
// somewhat_long_expression
// }
// // ...
// }
// ```
// - the block has no attribute and was not created inside a macro
// - if the block is an `anon_const`, the inner expr must be a literal
// (do not lint `struct A<const N: usize>; let _: A<{ 2 + 3 }>;`)
//
// FIXME(const_generics): handle paths when #67075 is fixed.
if let [stmt] = inner.stmts.as_slice() {
if let ast::StmtKind::Expr(ref expr) = stmt.kind {
if !Self::is_expr_delims_necessary(expr, followed_by_block)
&& (ctx != UnusedDelimsCtx::AnonConst
|| matches!(expr.kind, ast::ExprKind::Lit(_)))
// array length expressions are checked during `check_anon_const` and `check_ty`,
// once as `ArrayLenExpr` and once as `AnonConst`.
//
// As we do not want to lint this twice, we do not emit an error for
// `ArrayLenExpr` if `AnonConst` would do the same.
&& (ctx != UnusedDelimsCtx::ArrayLenExpr
|| !matches!(expr.kind, ast::ExprKind::Lit(_)))
&& !cx.sess().source_map().is_multiline(value.span)
&& value.attrs.is_empty()
&& !value.span.from_expansion()
{
self.emit_unused_delims_expr(cx, value, ctx, left_pos, right_pos)
}
}
}
}
ast::ExprKind::Let(_, ref expr) => {
// FIXME(#60336): Properly handle `let true = (false && true)`
// actually needing the parenthesis.
self.check_unused_delims_expr(
cx,
expr,
UnusedDelimsCtx::LetHeadExpr,
followed_by_block,
None,
None,
);
}
_ => {}
}
}
}
impl EarlyLintPass for UnusedBraces {
fn check_expr(&mut self, cx: &EarlyContext<'_>, e: &ast::Expr) {
<Self as UnusedDelimLint>::check_expr(self, cx, e)
}
fn check_anon_const(&mut self, cx: &EarlyContext<'_>, c: &ast::AnonConst) {
self.check_unused_delims_expr(cx, &c.value, UnusedDelimsCtx::AnonConst, false, None, None);
}
fn check_stmt(&mut self, cx: &EarlyContext<'_>, s: &ast::Stmt) {
<Self as UnusedDelimLint>::check_stmt(self, cx, s)
}
fn check_ty(&mut self, cx: &EarlyContext<'_>, ty: &ast::Ty) {
if let &ast::TyKind::Paren(ref r) = &ty.kind {
if let ast::TyKind::Array(_, ref len) = r.kind {
self.check_unused_delims_expr(
cx,
&len.value,
UnusedDelimsCtx::ArrayLenExpr,
false,
None,
None,
);
}
}
}
fn check_item(&mut self, cx: &EarlyContext<'_>, item: &ast::Item) {
<Self as UnusedDelimLint>::check_item(self, cx, item)
}
}
declare_lint! {
UNUSED_IMPORT_BRACES,
Allow,