mirror of https://github.com/rust-lang/rust.git
Merge pull request #477 from Manishearth/escape
Rudimentary escape analysis for Box<T>
This commit is contained in:
commit
5827240e17
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@ -6,7 +6,7 @@ A collection of lints to catch common mistakes and improve your Rust code.
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[Jump to usage instructions](#usage)
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[Jump to usage instructions](#usage)
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##Lints
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##Lints
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There are 80 lints included in this crate:
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There are 81 lints included in this crate:
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name | default | meaning
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name | default | meaning
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---------------------------------------------------------------------------------------------------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
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---------------------------------------------------------------------------------------------------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
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@ -15,6 +15,7 @@ name
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[block_in_if_condition_expr](https://github.com/Manishearth/rust-clippy/wiki#block_in_if_condition_expr) | warn | braces can be eliminated in conditions that are expressions, e.g `if { true } ...`
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[block_in_if_condition_expr](https://github.com/Manishearth/rust-clippy/wiki#block_in_if_condition_expr) | warn | braces can be eliminated in conditions that are expressions, e.g `if { true } ...`
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[block_in_if_condition_stmt](https://github.com/Manishearth/rust-clippy/wiki#block_in_if_condition_stmt) | warn | avoid complex blocks in conditions, instead move the block higher and bind it with 'let'; e.g: `if { let x = true; x } ...`
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[block_in_if_condition_stmt](https://github.com/Manishearth/rust-clippy/wiki#block_in_if_condition_stmt) | warn | avoid complex blocks in conditions, instead move the block higher and bind it with 'let'; e.g: `if { let x = true; x } ...`
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[box_vec](https://github.com/Manishearth/rust-clippy/wiki#box_vec) | warn | usage of `Box<Vec<T>>`, vector elements are already on the heap
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[box_vec](https://github.com/Manishearth/rust-clippy/wiki#box_vec) | warn | usage of `Box<Vec<T>>`, vector elements are already on the heap
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[boxed_local](https://github.com/Manishearth/rust-clippy/wiki#boxed_local) | warn | using Box<T> where unnecessary
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[cast_possible_truncation](https://github.com/Manishearth/rust-clippy/wiki#cast_possible_truncation) | allow | casts that may cause truncation of the value, e.g `x as u8` where `x: u32`, or `x as i32` where `x: f32`
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[cast_possible_truncation](https://github.com/Manishearth/rust-clippy/wiki#cast_possible_truncation) | allow | casts that may cause truncation of the value, e.g `x as u8` where `x: u32`, or `x as i32` where `x: f32`
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[cast_possible_wrap](https://github.com/Manishearth/rust-clippy/wiki#cast_possible_wrap) | allow | casts that may cause wrapping around the value, e.g `x as i32` where `x: u32` and `x > i32::MAX`
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[cast_possible_wrap](https://github.com/Manishearth/rust-clippy/wiki#cast_possible_wrap) | allow | casts that may cause wrapping around the value, e.g `x as i32` where `x: u32` and `x > i32::MAX`
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[cast_precision_loss](https://github.com/Manishearth/rust-clippy/wiki#cast_precision_loss) | allow | casts that cause loss of precision, e.g `x as f32` where `x: u64`
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[cast_precision_loss](https://github.com/Manishearth/rust-clippy/wiki#cast_precision_loss) | allow | casts that cause loss of precision, e.g `x as f32` where `x: u64`
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@ -0,0 +1,156 @@
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use rustc::lint::*;
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use rustc_front::hir::*;
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use rustc_front::intravisit as visit;
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use rustc::front::map::Node;
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use rustc::middle::ty;
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use rustc::middle::ty::adjustment::AutoAdjustment;
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use rustc::middle::expr_use_visitor::*;
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use rustc::middle::infer;
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use rustc::middle::mem_categorization::{cmt, Categorization};
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use rustc::util::nodemap::NodeSet;
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use syntax::ast::NodeId;
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use syntax::codemap::Span;
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use utils::span_lint;
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pub struct EscapePass;
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declare_lint!(pub BOXED_LOCAL, Warn, "using Box<T> where unnecessary");
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struct EscapeDelegate<'a, 'tcx: 'a> {
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cx: &'a LateContext<'a, 'tcx>,
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set: NodeSet,
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}
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impl LintPass for EscapePass {
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fn get_lints(&self) -> LintArray {
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lint_array!(BOXED_LOCAL)
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}
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}
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impl LateLintPass for EscapePass {
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fn check_fn(&mut self,
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cx: &LateContext,
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_: visit::FnKind,
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decl: &FnDecl,
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body: &Block,
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_: Span,
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id: NodeId) {
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let param_env = ty::ParameterEnvironment::for_item(cx.tcx, id);
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let infcx = infer::new_infer_ctxt(cx.tcx, &cx.tcx.tables, Some(param_env), false);
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let mut v = EscapeDelegate {
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cx: cx,
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set: NodeSet(),
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};
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{
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let mut vis = ExprUseVisitor::new(&mut v, &infcx);
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vis.walk_fn(decl, body);
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}
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for node in v.set {
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span_lint(cx,
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BOXED_LOCAL,
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cx.tcx.map.span(node),
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"local variable doesn't need to be boxed here");
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}
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}
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}
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impl<'a, 'tcx: 'a> Delegate<'tcx> for EscapeDelegate<'a, 'tcx> {
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fn consume(&mut self,
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_: NodeId,
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_: Span,
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cmt: cmt<'tcx>,
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mode: ConsumeMode) {
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if let Categorization::Local(lid) = cmt.cat {
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if self.set.contains(&lid) {
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if let Move(DirectRefMove) = mode {
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// moved out or in. clearly can't be localized
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self.set.remove(&lid);
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}
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}
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}
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}
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fn matched_pat(&mut self, _: &Pat, _: cmt<'tcx>, _: MatchMode) {}
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fn consume_pat(&mut self, consume_pat: &Pat, cmt: cmt<'tcx>, _: ConsumeMode) {
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if let Categorization::Rvalue(..) = cmt.cat {
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if let Some(Node::NodeStmt(st)) = self.cx
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.tcx
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.map
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.find(self.cx.tcx.map.get_parent_node(cmt.id)) {
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if let StmtDecl(ref decl, _) = st.node {
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if let DeclLocal(ref loc) = decl.node {
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if let Some(ref ex) = loc.init {
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if let ExprBox(..) = ex.node {
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if let ty::TyBox(..) = cmt.ty.sty {
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// let x = box (...)
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self.set.insert(consume_pat.id);
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}
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// TODO Box::new
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// TODO vec![]
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// TODO "foo".to_owned() and friends
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}
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}
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}
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}
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}
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}
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if let Categorization::Local(lid) = cmt.cat {
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if self.set.contains(&lid) {
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// let y = x where x is known
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// remove x, insert y
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self.set.insert(consume_pat.id);
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self.set.remove(&lid);
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}
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}
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}
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fn borrow(&mut self,
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borrow_id: NodeId,
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_: Span,
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cmt: cmt<'tcx>,
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_: ty::Region,
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_: ty::BorrowKind,
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loan_cause: LoanCause) {
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if let Categorization::Local(lid) = cmt.cat {
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if self.set.contains(&lid) {
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if let Some(&AutoAdjustment::AdjustDerefRef(adj)) = self.cx
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.tcx
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.tables
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.borrow()
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.adjustments
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.get(&borrow_id) {
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if LoanCause::AutoRef == loan_cause {
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// x.foo()
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if adj.autoderefs <= 0 {
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self.set.remove(&lid); // Used without autodereffing (i.e. x.clone())
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}
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} else {
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self.cx.sess().span_bug(cmt.span, "Unknown adjusted AutoRef");
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}
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} else if LoanCause::AddrOf == loan_cause {
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// &x
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if let Some(&AutoAdjustment::AdjustDerefRef(adj)) =
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self.cx.tcx.tables.borrow().adjustments
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.get(&self.cx.tcx.map.get_parent_node(borrow_id)) {
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if adj.autoderefs <= 1 {
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// foo(&x) where no extra autoreffing is happening
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self.set.remove(&lid);
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}
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}
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} else if LoanCause::MatchDiscriminant == loan_cause {
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self.set.remove(&lid); // `match x` can move
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}
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// do nothing for matches, etc. These can't escape
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}
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}
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}
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fn decl_without_init(&mut self, _: NodeId, _: Span) {}
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fn mutate(&mut self,
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_: NodeId,
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_: Span,
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_: cmt<'tcx>,
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_: MutateMode) {
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}
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}
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@ -64,6 +64,7 @@ pub mod no_effect;
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pub mod temporary_assignment;
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pub mod temporary_assignment;
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pub mod transmute;
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pub mod transmute;
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pub mod cyclomatic_complexity;
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pub mod cyclomatic_complexity;
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pub mod escape;
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mod reexport {
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mod reexport {
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pub use syntax::ast::{Name, Ident, NodeId};
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pub use syntax::ast::{Name, Ident, NodeId};
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@ -116,6 +117,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
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reg.register_late_lint_pass(box temporary_assignment::TemporaryAssignmentPass);
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reg.register_late_lint_pass(box temporary_assignment::TemporaryAssignmentPass);
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reg.register_late_lint_pass(box transmute::UselessTransmute);
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reg.register_late_lint_pass(box transmute::UselessTransmute);
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reg.register_late_lint_pass(box cyclomatic_complexity::CyclomaticComplexity::new(25));
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reg.register_late_lint_pass(box cyclomatic_complexity::CyclomaticComplexity::new(25));
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reg.register_late_lint_pass(box escape::EscapePass);
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reg.register_lint_group("clippy_pedantic", vec![
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reg.register_lint_group("clippy_pedantic", vec![
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methods::OPTION_UNWRAP_USED,
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methods::OPTION_UNWRAP_USED,
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@ -146,6 +148,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
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collapsible_if::COLLAPSIBLE_IF,
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collapsible_if::COLLAPSIBLE_IF,
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cyclomatic_complexity::CYCLOMATIC_COMPLEXITY,
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cyclomatic_complexity::CYCLOMATIC_COMPLEXITY,
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eq_op::EQ_OP,
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eq_op::EQ_OP,
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escape::BOXED_LOCAL,
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eta_reduction::REDUNDANT_CLOSURE,
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eta_reduction::REDUNDANT_CLOSURE,
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identity_op::IDENTITY_OP,
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identity_op::IDENTITY_OP,
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len_zero::LEN_WITHOUT_IS_EMPTY,
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len_zero::LEN_WITHOUT_IS_EMPTY,
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@ -0,0 +1,81 @@
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#![feature(plugin, box_syntax)]
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#![plugin(clippy)]
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#![allow(warnings, clippy)]
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#![deny(boxed_local)]
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#[derive(Clone)]
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struct A;
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impl A {
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fn foo(&self){}
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}
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fn main() {
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}
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fn warn_call() {
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let x = box A; //~ ERROR local variable
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x.foo();
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}
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fn warn_rename_call() {
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let x = box A;
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let y = x; //~ ERROR local variable
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y.foo(); // via autoderef
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}
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fn warn_notuse() {
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let bz = box A; //~ ERROR local variable
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}
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fn warn_pass() {
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let bz = box A; //~ ERROR local variable
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take_ref(&bz); // via deref coercion
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}
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fn nowarn_return() -> Box<A> {
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let fx = box A;
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fx // moved out, "escapes"
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}
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fn nowarn_move() {
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let bx = box A;
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drop(bx) // moved in, "escapes"
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}
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fn nowarn_call() {
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let bx = box A;
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bx.clone(); // method only available to Box, not via autoderef
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}
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fn nowarn_pass() {
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let bx = box A;
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take_box(&bx); // fn needs &Box
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}
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fn take_box(x: &Box<A>) {}
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fn take_ref(x: &A) {}
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fn nowarn_ref_take() {
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// false positive, should actually warn
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let x = box A; //~ ERROR local variable
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let y = &x;
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take_box(y);
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}
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fn nowarn_match() {
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let x = box A; // moved into a match
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match x {
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y => drop(y)
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}
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}
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fn warn_match() {
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let x = box A; //~ ERROR local variable
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match &x { // not moved
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ref y => ()
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}
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}
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