From 455d0476b11c1a1a2ae8005e781c6ea9b2f4d2ac Mon Sep 17 00:00:00 2001 From: nahuakang Date: Sun, 21 Feb 2021 15:58:05 +0100 Subject: [PATCH] Refactor never loop to its own module --- clippy_lints/src/loops/mod.rs | 173 +-------------------------- clippy_lints/src/loops/never_loop.rs | 172 ++++++++++++++++++++++++++ 2 files changed, 176 insertions(+), 169 deletions(-) create mode 100644 clippy_lints/src/loops/never_loop.rs diff --git a/clippy_lints/src/loops/mod.rs b/clippy_lints/src/loops/mod.rs index c6055e34eb2..9a4cbf27c49 100644 --- a/clippy_lints/src/loops/mod.rs +++ b/clippy_lints/src/loops/mod.rs @@ -8,6 +8,7 @@ mod infinite_loop; mod manual_flatten; mod manual_memcpy; mod needless_collect; +mod never_loop; mod same_item_push; mod utils; @@ -16,21 +17,18 @@ use crate::utils::usage::mutated_variables; use crate::utils::{ get_enclosing_block, get_trait_def_id, higher, implements_trait, is_in_panic_handler, is_no_std_crate, is_refutable, last_path_segment, match_trait_method, path_to_local, path_to_local_id, paths, - snippet_with_applicability, span_lint, span_lint_and_help, span_lint_and_sugg, sugg, + snippet_with_applicability, span_lint_and_help, span_lint_and_sugg, sugg, }; use if_chain::if_chain; use rustc_errors::Applicability; use rustc_hir::intravisit::{walk_block, walk_expr, NestedVisitorMap, Visitor}; -use rustc_hir::{ - Block, Expr, ExprKind, HirId, InlineAsmOperand, LoopSource, MatchSource, Node, Pat, PatKind, Stmt, StmtKind, -}; +use rustc_hir::{Block, Expr, ExprKind, HirId, LoopSource, MatchSource, Node, Pat, PatKind, StmtKind}; use rustc_lint::{LateContext, LateLintPass, LintContext}; use rustc_middle::hir::map::Map; use rustc_middle::lint::in_external_macro; use rustc_session::{declare_lint_pass, declare_tool_lint}; use rustc_span::source_map::Span; use rustc_span::symbol::sym; -use std::iter::{once, Iterator}; use utils::{ get_span_of_entire_for_loop, make_iterator_snippet, IncrementVisitor, InitializeVisitor, LoopNestVisitor, Nesting, }; @@ -567,12 +565,7 @@ impl<'tcx> LateLintPass<'tcx> for Loops { } // check for never_loop - if let ExprKind::Loop(ref block, _, _, _) = expr.kind { - match never_loop_block(block, expr.hir_id) { - NeverLoopResult::AlwaysBreak => span_lint(cx, NEVER_LOOP, expr.span, "this loop never actually loops"), - NeverLoopResult::MayContinueMainLoop | NeverLoopResult::Otherwise => (), - } - } + never_loop::check_never_loop(cx, expr); // check for `loop { if let {} else break }` that could be `while let` // (also matches an explicit "match" instead of "if let") @@ -689,164 +682,6 @@ impl<'tcx> LateLintPass<'tcx> for Loops { } } -enum NeverLoopResult { - // A break/return always get triggered but not necessarily for the main loop. - AlwaysBreak, - // A continue may occur for the main loop. - MayContinueMainLoop, - Otherwise, -} - -#[must_use] -fn absorb_break(arg: &NeverLoopResult) -> NeverLoopResult { - match *arg { - NeverLoopResult::AlwaysBreak | NeverLoopResult::Otherwise => NeverLoopResult::Otherwise, - NeverLoopResult::MayContinueMainLoop => NeverLoopResult::MayContinueMainLoop, - } -} - -// Combine two results for parts that are called in order. -#[must_use] -fn combine_seq(first: NeverLoopResult, second: NeverLoopResult) -> NeverLoopResult { - match first { - NeverLoopResult::AlwaysBreak | NeverLoopResult::MayContinueMainLoop => first, - NeverLoopResult::Otherwise => second, - } -} - -// Combine two results where both parts are called but not necessarily in order. -#[must_use] -fn combine_both(left: NeverLoopResult, right: NeverLoopResult) -> NeverLoopResult { - match (left, right) { - (NeverLoopResult::MayContinueMainLoop, _) | (_, NeverLoopResult::MayContinueMainLoop) => { - NeverLoopResult::MayContinueMainLoop - }, - (NeverLoopResult::AlwaysBreak, _) | (_, NeverLoopResult::AlwaysBreak) => NeverLoopResult::AlwaysBreak, - (NeverLoopResult::Otherwise, NeverLoopResult::Otherwise) => NeverLoopResult::Otherwise, - } -} - -// Combine two results where only one of the part may have been executed. -#[must_use] -fn combine_branches(b1: NeverLoopResult, b2: NeverLoopResult) -> NeverLoopResult { - match (b1, b2) { - (NeverLoopResult::AlwaysBreak, NeverLoopResult::AlwaysBreak) => NeverLoopResult::AlwaysBreak, - (NeverLoopResult::MayContinueMainLoop, _) | (_, NeverLoopResult::MayContinueMainLoop) => { - NeverLoopResult::MayContinueMainLoop - }, - (NeverLoopResult::Otherwise, _) | (_, NeverLoopResult::Otherwise) => NeverLoopResult::Otherwise, - } -} - -fn never_loop_block(block: &Block<'_>, main_loop_id: HirId) -> NeverLoopResult { - let stmts = block.stmts.iter().map(stmt_to_expr); - let expr = once(block.expr.as_deref()); - let mut iter = stmts.chain(expr).flatten(); - never_loop_expr_seq(&mut iter, main_loop_id) -} - -fn stmt_to_expr<'tcx>(stmt: &Stmt<'tcx>) -> Option<&'tcx Expr<'tcx>> { - match stmt.kind { - StmtKind::Semi(ref e, ..) | StmtKind::Expr(ref e, ..) => Some(e), - StmtKind::Local(ref local) => local.init.as_deref(), - _ => None, - } -} - -fn never_loop_expr(expr: &Expr<'_>, main_loop_id: HirId) -> NeverLoopResult { - match expr.kind { - ExprKind::Box(ref e) - | ExprKind::Unary(_, ref e) - | ExprKind::Cast(ref e, _) - | ExprKind::Type(ref e, _) - | ExprKind::Field(ref e, _) - | ExprKind::AddrOf(_, _, ref e) - | ExprKind::Struct(_, _, Some(ref e)) - | ExprKind::Repeat(ref e, _) - | ExprKind::DropTemps(ref e) => never_loop_expr(e, main_loop_id), - ExprKind::Array(ref es) | ExprKind::MethodCall(_, _, ref es, _) | ExprKind::Tup(ref es) => { - never_loop_expr_all(&mut es.iter(), main_loop_id) - }, - ExprKind::Call(ref e, ref es) => never_loop_expr_all(&mut once(&**e).chain(es.iter()), main_loop_id), - ExprKind::Binary(_, ref e1, ref e2) - | ExprKind::Assign(ref e1, ref e2, _) - | ExprKind::AssignOp(_, ref e1, ref e2) - | ExprKind::Index(ref e1, ref e2) => never_loop_expr_all(&mut [&**e1, &**e2].iter().cloned(), main_loop_id), - ExprKind::Loop(ref b, _, _, _) => { - // Break can come from the inner loop so remove them. - absorb_break(&never_loop_block(b, main_loop_id)) - }, - ExprKind::If(ref e, ref e2, ref e3) => { - let e1 = never_loop_expr(e, main_loop_id); - let e2 = never_loop_expr(e2, main_loop_id); - let e3 = e3 - .as_ref() - .map_or(NeverLoopResult::Otherwise, |e| never_loop_expr(e, main_loop_id)); - combine_seq(e1, combine_branches(e2, e3)) - }, - ExprKind::Match(ref e, ref arms, _) => { - let e = never_loop_expr(e, main_loop_id); - if arms.is_empty() { - e - } else { - let arms = never_loop_expr_branch(&mut arms.iter().map(|a| &*a.body), main_loop_id); - combine_seq(e, arms) - } - }, - ExprKind::Block(ref b, _) => never_loop_block(b, main_loop_id), - ExprKind::Continue(d) => { - let id = d - .target_id - .expect("target ID can only be missing in the presence of compilation errors"); - if id == main_loop_id { - NeverLoopResult::MayContinueMainLoop - } else { - NeverLoopResult::AlwaysBreak - } - }, - ExprKind::Break(_, ref e) | ExprKind::Ret(ref e) => e.as_ref().map_or(NeverLoopResult::AlwaysBreak, |e| { - combine_seq(never_loop_expr(e, main_loop_id), NeverLoopResult::AlwaysBreak) - }), - ExprKind::InlineAsm(ref asm) => asm - .operands - .iter() - .map(|(o, _)| match o { - InlineAsmOperand::In { expr, .. } - | InlineAsmOperand::InOut { expr, .. } - | InlineAsmOperand::Const { expr } - | InlineAsmOperand::Sym { expr } => never_loop_expr(expr, main_loop_id), - InlineAsmOperand::Out { expr, .. } => never_loop_expr_all(&mut expr.iter(), main_loop_id), - InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => { - never_loop_expr_all(&mut once(in_expr).chain(out_expr.iter()), main_loop_id) - }, - }) - .fold(NeverLoopResult::Otherwise, combine_both), - ExprKind::Struct(_, _, None) - | ExprKind::Yield(_, _) - | ExprKind::Closure(_, _, _, _, _) - | ExprKind::LlvmInlineAsm(_) - | ExprKind::Path(_) - | ExprKind::ConstBlock(_) - | ExprKind::Lit(_) - | ExprKind::Err => NeverLoopResult::Otherwise, - } -} - -fn never_loop_expr_seq<'a, T: Iterator>>(es: &mut T, main_loop_id: HirId) -> NeverLoopResult { - es.map(|e| never_loop_expr(e, main_loop_id)) - .fold(NeverLoopResult::Otherwise, combine_seq) -} - -fn never_loop_expr_all<'a, T: Iterator>>(es: &mut T, main_loop_id: HirId) -> NeverLoopResult { - es.map(|e| never_loop_expr(e, main_loop_id)) - .fold(NeverLoopResult::Otherwise, combine_both) -} - -fn never_loop_expr_branch<'a, T: Iterator>>(e: &mut T, main_loop_id: HirId) -> NeverLoopResult { - e.map(|e| never_loop_expr(e, main_loop_id)) - .fold(NeverLoopResult::AlwaysBreak, combine_branches) -} - fn check_for_loop<'tcx>( cx: &LateContext<'tcx>, pat: &'tcx Pat<'_>, diff --git a/clippy_lints/src/loops/never_loop.rs b/clippy_lints/src/loops/never_loop.rs new file mode 100644 index 00000000000..d51ff81103f --- /dev/null +++ b/clippy_lints/src/loops/never_loop.rs @@ -0,0 +1,172 @@ +use super::NEVER_LOOP; +use crate::utils::span_lint; +use rustc_hir::{Block, Expr, ExprKind, HirId, InlineAsmOperand, Stmt, StmtKind}; +use rustc_lint::LateContext; +use std::iter::{once, Iterator}; + +pub(super) fn check_never_loop(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { + if let ExprKind::Loop(ref block, _, _, _) = expr.kind { + match never_loop_block(block, expr.hir_id) { + NeverLoopResult::AlwaysBreak => span_lint(cx, NEVER_LOOP, expr.span, "this loop never actually loops"), + NeverLoopResult::MayContinueMainLoop | NeverLoopResult::Otherwise => (), + } + } +} + +enum NeverLoopResult { + // A break/return always get triggered but not necessarily for the main loop. + AlwaysBreak, + // A continue may occur for the main loop. + MayContinueMainLoop, + Otherwise, +} + +#[must_use] +fn absorb_break(arg: &NeverLoopResult) -> NeverLoopResult { + match *arg { + NeverLoopResult::AlwaysBreak | NeverLoopResult::Otherwise => NeverLoopResult::Otherwise, + NeverLoopResult::MayContinueMainLoop => NeverLoopResult::MayContinueMainLoop, + } +} + +// Combine two results for parts that are called in order. +#[must_use] +fn combine_seq(first: NeverLoopResult, second: NeverLoopResult) -> NeverLoopResult { + match first { + NeverLoopResult::AlwaysBreak | NeverLoopResult::MayContinueMainLoop => first, + NeverLoopResult::Otherwise => second, + } +} + +// Combine two results where both parts are called but not necessarily in order. +#[must_use] +fn combine_both(left: NeverLoopResult, right: NeverLoopResult) -> NeverLoopResult { + match (left, right) { + (NeverLoopResult::MayContinueMainLoop, _) | (_, NeverLoopResult::MayContinueMainLoop) => { + NeverLoopResult::MayContinueMainLoop + }, + (NeverLoopResult::AlwaysBreak, _) | (_, NeverLoopResult::AlwaysBreak) => NeverLoopResult::AlwaysBreak, + (NeverLoopResult::Otherwise, NeverLoopResult::Otherwise) => NeverLoopResult::Otherwise, + } +} + +// Combine two results where only one of the part may have been executed. +#[must_use] +fn combine_branches(b1: NeverLoopResult, b2: NeverLoopResult) -> NeverLoopResult { + match (b1, b2) { + (NeverLoopResult::AlwaysBreak, NeverLoopResult::AlwaysBreak) => NeverLoopResult::AlwaysBreak, + (NeverLoopResult::MayContinueMainLoop, _) | (_, NeverLoopResult::MayContinueMainLoop) => { + NeverLoopResult::MayContinueMainLoop + }, + (NeverLoopResult::Otherwise, _) | (_, NeverLoopResult::Otherwise) => NeverLoopResult::Otherwise, + } +} + +fn never_loop_block(block: &Block<'_>, main_loop_id: HirId) -> NeverLoopResult { + let stmts = block.stmts.iter().map(stmt_to_expr); + let expr = once(block.expr.as_deref()); + let mut iter = stmts.chain(expr).flatten(); + never_loop_expr_seq(&mut iter, main_loop_id) +} + +fn never_loop_expr_seq<'a, T: Iterator>>(es: &mut T, main_loop_id: HirId) -> NeverLoopResult { + es.map(|e| never_loop_expr(e, main_loop_id)) + .fold(NeverLoopResult::Otherwise, combine_seq) +} + +fn stmt_to_expr<'tcx>(stmt: &Stmt<'tcx>) -> Option<&'tcx Expr<'tcx>> { + match stmt.kind { + StmtKind::Semi(ref e, ..) | StmtKind::Expr(ref e, ..) => Some(e), + StmtKind::Local(ref local) => local.init.as_deref(), + _ => None, + } +} + +fn never_loop_expr(expr: &Expr<'_>, main_loop_id: HirId) -> NeverLoopResult { + match expr.kind { + ExprKind::Box(ref e) + | ExprKind::Unary(_, ref e) + | ExprKind::Cast(ref e, _) + | ExprKind::Type(ref e, _) + | ExprKind::Field(ref e, _) + | ExprKind::AddrOf(_, _, ref e) + | ExprKind::Struct(_, _, Some(ref e)) + | ExprKind::Repeat(ref e, _) + | ExprKind::DropTemps(ref e) => never_loop_expr(e, main_loop_id), + ExprKind::Array(ref es) | ExprKind::MethodCall(_, _, ref es, _) | ExprKind::Tup(ref es) => { + never_loop_expr_all(&mut es.iter(), main_loop_id) + }, + ExprKind::Call(ref e, ref es) => never_loop_expr_all(&mut once(&**e).chain(es.iter()), main_loop_id), + ExprKind::Binary(_, ref e1, ref e2) + | ExprKind::Assign(ref e1, ref e2, _) + | ExprKind::AssignOp(_, ref e1, ref e2) + | ExprKind::Index(ref e1, ref e2) => never_loop_expr_all(&mut [&**e1, &**e2].iter().cloned(), main_loop_id), + ExprKind::Loop(ref b, _, _, _) => { + // Break can come from the inner loop so remove them. + absorb_break(&never_loop_block(b, main_loop_id)) + }, + ExprKind::If(ref e, ref e2, ref e3) => { + let e1 = never_loop_expr(e, main_loop_id); + let e2 = never_loop_expr(e2, main_loop_id); + let e3 = e3 + .as_ref() + .map_or(NeverLoopResult::Otherwise, |e| never_loop_expr(e, main_loop_id)); + combine_seq(e1, combine_branches(e2, e3)) + }, + ExprKind::Match(ref e, ref arms, _) => { + let e = never_loop_expr(e, main_loop_id); + if arms.is_empty() { + e + } else { + let arms = never_loop_expr_branch(&mut arms.iter().map(|a| &*a.body), main_loop_id); + combine_seq(e, arms) + } + }, + ExprKind::Block(ref b, _) => never_loop_block(b, main_loop_id), + ExprKind::Continue(d) => { + let id = d + .target_id + .expect("target ID can only be missing in the presence of compilation errors"); + if id == main_loop_id { + NeverLoopResult::MayContinueMainLoop + } else { + NeverLoopResult::AlwaysBreak + } + }, + ExprKind::Break(_, ref e) | ExprKind::Ret(ref e) => e.as_ref().map_or(NeverLoopResult::AlwaysBreak, |e| { + combine_seq(never_loop_expr(e, main_loop_id), NeverLoopResult::AlwaysBreak) + }), + ExprKind::InlineAsm(ref asm) => asm + .operands + .iter() + .map(|(o, _)| match o { + InlineAsmOperand::In { expr, .. } + | InlineAsmOperand::InOut { expr, .. } + | InlineAsmOperand::Const { expr } + | InlineAsmOperand::Sym { expr } => never_loop_expr(expr, main_loop_id), + InlineAsmOperand::Out { expr, .. } => never_loop_expr_all(&mut expr.iter(), main_loop_id), + InlineAsmOperand::SplitInOut { in_expr, out_expr, .. } => { + never_loop_expr_all(&mut once(in_expr).chain(out_expr.iter()), main_loop_id) + }, + }) + .fold(NeverLoopResult::Otherwise, combine_both), + ExprKind::Struct(_, _, None) + | ExprKind::Yield(_, _) + | ExprKind::Closure(_, _, _, _, _) + | ExprKind::LlvmInlineAsm(_) + | ExprKind::Path(_) + | ExprKind::ConstBlock(_) + | ExprKind::Lit(_) + | ExprKind::Err => NeverLoopResult::Otherwise, + } +} + +fn never_loop_expr_all<'a, T: Iterator>>(es: &mut T, main_loop_id: HirId) -> NeverLoopResult { + es.map(|e| never_loop_expr(e, main_loop_id)) + .fold(NeverLoopResult::Otherwise, combine_both) +} + +fn never_loop_expr_branch<'a, T: Iterator>>(e: &mut T, main_loop_id: HirId) -> NeverLoopResult { + e.map(|e| never_loop_expr(e, main_loop_id)) + .fold(NeverLoopResult::AlwaysBreak, combine_branches) +}