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|
use clippy_utils::consts::{constant_simple, Constant};
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::snippet;
use clippy_utils::ty::match_type;
use clippy_utils::{def_path_def_ids, is_expn_of, match_def_path, paths};
use if_chain::if_chain;
use rustc_data_structures::fx::FxHashMap;
use rustc_errors::Applicability;
use rustc_hir::def::{DefKind, Res};
use rustc_hir::def_id::DefId;
use rustc_hir::{BinOpKind, Expr, ExprKind, UnOp};
use rustc_lint::{LateContext, LateLintPass};
use rustc_middle::mir::interpret::ConstValue;
use rustc_middle::ty::{self};
use rustc_session::{declare_tool_lint, impl_lint_pass};
use rustc_span::symbol::Symbol;
use std::borrow::Cow;
declare_clippy_lint! {
/// ### What it does
/// Checks for interning symbols that have already been pre-interned and defined as constants.
///
/// ### Why is this bad?
/// It's faster and easier to use the symbol constant.
///
/// ### Example
/// ```rust,ignore
/// let _ = sym!(f32);
/// ```
///
/// Use instead:
/// ```rust,ignore
/// let _ = sym::f32;
/// ```
pub INTERNING_DEFINED_SYMBOL,
internal,
"interning a symbol that is pre-interned and defined as a constant"
}
declare_clippy_lint! {
/// ### What it does
/// Checks for unnecessary conversion from Symbol to a string.
///
/// ### Why is this bad?
/// It's faster use symbols directly instead of strings.
///
/// ### Example
/// ```rust,ignore
/// symbol.as_str() == "clippy";
/// ```
///
/// Use instead:
/// ```rust,ignore
/// symbol == sym::clippy;
/// ```
pub UNNECESSARY_SYMBOL_STR,
internal,
"unnecessary conversion between Symbol and string"
}
#[derive(Default)]
pub struct InterningDefinedSymbol {
// Maps the symbol value to the constant DefId.
symbol_map: FxHashMap<u32, DefId>,
}
impl_lint_pass!(InterningDefinedSymbol => [INTERNING_DEFINED_SYMBOL, UNNECESSARY_SYMBOL_STR]);
impl<'tcx> LateLintPass<'tcx> for InterningDefinedSymbol {
fn check_crate(&mut self, cx: &LateContext<'_>) {
if !self.symbol_map.is_empty() {
return;
}
for &module in &[&paths::KW_MODULE, &paths::SYM_MODULE] {
for def_id in def_path_def_ids(cx, module) {
for item in cx.tcx.module_children(def_id).iter() {
if_chain! {
if let Res::Def(DefKind::Const, item_def_id) = item.res;
let ty = cx.tcx.type_of(item_def_id).subst_identity();
if match_type(cx, ty, &paths::SYMBOL);
if let Ok(ConstValue::Scalar(value)) = cx.tcx.const_eval_poly(item_def_id);
if let Ok(value) = value.to_u32();
then {
self.symbol_map.insert(value, item_def_id);
}
}
}
}
}
}
fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
if_chain! {
if let ExprKind::Call(func, [arg]) = &expr.kind;
if let ty::FnDef(def_id, _) = cx.typeck_results().expr_ty(func).kind();
if match_def_path(cx, *def_id, &paths::SYMBOL_INTERN);
if let Some(Constant::Str(arg)) = constant_simple(cx, cx.typeck_results(), arg);
let value = Symbol::intern(&arg).as_u32();
if let Some(&def_id) = self.symbol_map.get(&value);
then {
span_lint_and_sugg(
cx,
INTERNING_DEFINED_SYMBOL,
is_expn_of(expr.span, "sym").unwrap_or(expr.span),
"interning a defined symbol",
"try",
cx.tcx.def_path_str(def_id),
Applicability::MachineApplicable,
);
}
}
if let ExprKind::Binary(op, left, right) = expr.kind {
if matches!(op.node, BinOpKind::Eq | BinOpKind::Ne) {
let data = [
(left, self.symbol_str_expr(left, cx)),
(right, self.symbol_str_expr(right, cx)),
];
match data {
// both operands are a symbol string
[(_, Some(left)), (_, Some(right))] => {
span_lint_and_sugg(
cx,
UNNECESSARY_SYMBOL_STR,
expr.span,
"unnecessary `Symbol` to string conversion",
"try",
format!(
"{} {} {}",
left.as_symbol_snippet(cx),
op.node.as_str(),
right.as_symbol_snippet(cx),
),
Applicability::MachineApplicable,
);
},
// one of the operands is a symbol string
[(expr, Some(symbol)), _] | [_, (expr, Some(symbol))] => {
// creating an owned string for comparison
if matches!(symbol, SymbolStrExpr::Expr { is_to_owned: true, .. }) {
span_lint_and_sugg(
cx,
UNNECESSARY_SYMBOL_STR,
expr.span,
"unnecessary string allocation",
"try",
format!("{}.as_str()", symbol.as_symbol_snippet(cx)),
Applicability::MachineApplicable,
);
}
},
// nothing found
[(_, None), (_, None)] => {},
}
}
}
}
}
impl InterningDefinedSymbol {
fn symbol_str_expr<'tcx>(&self, expr: &'tcx Expr<'tcx>, cx: &LateContext<'tcx>) -> Option<SymbolStrExpr<'tcx>> {
static IDENT_STR_PATHS: &[&[&str]] = &[&paths::IDENT_AS_STR, &paths::TO_STRING_METHOD];
static SYMBOL_STR_PATHS: &[&[&str]] = &[
&paths::SYMBOL_AS_STR,
&paths::SYMBOL_TO_IDENT_STRING,
&paths::TO_STRING_METHOD,
];
let call = if_chain! {
if let ExprKind::AddrOf(_, _, e) = expr.kind;
if let ExprKind::Unary(UnOp::Deref, e) = e.kind;
then { e } else { expr }
};
if_chain! {
// is a method call
if let ExprKind::MethodCall(_, item, [], _) = call.kind;
if let Some(did) = cx.typeck_results().type_dependent_def_id(call.hir_id);
let ty = cx.typeck_results().expr_ty(item);
// ...on either an Ident or a Symbol
if let Some(is_ident) = if match_type(cx, ty, &paths::SYMBOL) {
Some(false)
} else if match_type(cx, ty, &paths::IDENT) {
Some(true)
} else {
None
};
// ...which converts it to a string
let paths = if is_ident { IDENT_STR_PATHS } else { SYMBOL_STR_PATHS };
if let Some(path) = paths.iter().find(|path| match_def_path(cx, did, path));
then {
let is_to_owned = path.last().unwrap().ends_with("string");
return Some(SymbolStrExpr::Expr {
item,
is_ident,
is_to_owned,
});
}
}
// is a string constant
if let Some(Constant::Str(s)) = constant_simple(cx, cx.typeck_results(), expr) {
let value = Symbol::intern(&s).as_u32();
// ...which matches a symbol constant
if let Some(&def_id) = self.symbol_map.get(&value) {
return Some(SymbolStrExpr::Const(def_id));
}
}
None
}
}
enum SymbolStrExpr<'tcx> {
/// a string constant with a corresponding symbol constant
Const(DefId),
/// a "symbol to string" expression like `symbol.as_str()`
Expr {
/// part that evaluates to `Symbol` or `Ident`
item: &'tcx Expr<'tcx>,
is_ident: bool,
/// whether an owned `String` is created like `to_ident_string()`
is_to_owned: bool,
},
}
impl<'tcx> SymbolStrExpr<'tcx> {
/// Returns a snippet that evaluates to a `Symbol` and is const if possible
fn as_symbol_snippet(&self, cx: &LateContext<'_>) -> Cow<'tcx, str> {
match *self {
Self::Const(def_id) => cx.tcx.def_path_str(def_id).into(),
Self::Expr { item, is_ident, .. } => {
let mut snip = snippet(cx, item.span.source_callsite(), "..");
if is_ident {
// get `Ident.name`
snip.to_mut().push_str(".name");
}
snip
},
}
}
}
|
