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Diffstat (limited to '')
| -rw-r--r-- | src/tools/clippy/clippy_lints/src/utils/internal_lints/interning_defined_symbol.rs | 239 |
1 files changed, 239 insertions, 0 deletions
diff --git a/src/tools/clippy/clippy_lints/src/utils/internal_lints/interning_defined_symbol.rs b/src/tools/clippy/clippy_lints/src/utils/internal_lints/interning_defined_symbol.rs new file mode 100644 index 000000000..096b60157 --- /dev/null +++ b/src/tools/clippy/clippy_lints/src/utils/internal_lints/interning_defined_symbol.rs @@ -0,0 +1,239 @@ +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_res, 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] { + if let Some(def_id) = def_path_res(cx, module, None).opt_def_id() { + 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); + 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 + }, + } + } +} |