lint on binding-names that are too similar

src/consts.rs

@@ -82,7 +82,7 @@ impl Constant {
 impl PartialEq for Constant {
     fn eq(&self, other: &Constant) -> bool {
         match (self, other) {
-            (&Constant::Str(ref ls, ref lsty), &Constant::Str(ref rs, ref rsty)) => ls == rs && lsty == rsty,
+            (&Constant::Str(ref ls, ref l_sty), &Constant::Str(ref rs, ref r_sty)) => ls == rs && l_sty == r_sty,
             (&Constant::Binary(ref l), &Constant::Binary(ref r)) => l == r,
             (&Constant::Char(l), &Constant::Char(r)) => l == r,
             (&Constant::Int(l), &Constant::Int(r)) => l.is_negative() == r.is_negative() && l.to_u64_unchecked() == r.to_u64_unchecked(),
@@ -145,8 +145,8 @@ impl Hash for Constant {
 impl PartialOrd for Constant {
     fn partial_cmp(&self, other: &Constant) -> Option<Ordering> {
         match (self, other) {
-            (&Constant::Str(ref ls, ref lsty), &Constant::Str(ref rs, ref rsty)) => {
-                if lsty == rsty {
+            (&Constant::Str(ref ls, ref l_sty), &Constant::Str(ref rs, ref r_sty)) => {
+                if l_sty == r_sty {
                     Some(ls.cmp(rs))
                 } else {
                     None
@@ -354,6 +354,7 @@ impl<'c, 'cc> ConstEvalLateContext<'c, 'cc> {
         }
     }
 
+
     fn binop_apply<F>(&mut self, left: &Expr, right: &Expr, op: F) -> Option<Constant>
         where F: Fn(Constant, Constant) -> Option<Constant>
     {

src/lib.rs

@@ -31,6 +31,9 @@ extern crate unicode_normalization;
 // for semver check in attrs.rs
 extern crate semver;
 
+// for levensthein distance
+extern crate strsim;
+
 // for regex checking
 extern crate regex_syntax;
 
@@ -84,6 +87,7 @@ pub mod needless_features;
 pub mod needless_update;
 pub mod new_without_default;
 pub mod no_effect;
+pub mod non_expressive_names;
 pub mod open_options;
 pub mod overflow_check_conditional;
 pub mod panic;
@@ -200,6 +204,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
     reg.register_late_lint_pass(box types::CharLitAsU8);
     reg.register_late_lint_pass(box print::PrintLint);
     reg.register_late_lint_pass(box vec::UselessVec);
+    reg.register_early_lint_pass(box non_expressive_names::SimilarNames(1));
     reg.register_late_lint_pass(box drop_ref::DropRefPass);
     reg.register_late_lint_pass(box types::AbsurdExtremeComparisons);
     reg.register_late_lint_pass(box regex::RegexPass::default());
@@ -326,6 +331,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
         needless_update::NEEDLESS_UPDATE,
         new_without_default::NEW_WITHOUT_DEFAULT,
         no_effect::NO_EFFECT,
+        non_expressive_names::SIMILAR_NAMES,
         open_options::NONSENSICAL_OPEN_OPTIONS,
         overflow_check_conditional::OVERFLOW_CHECK_CONDITIONAL,
         panic::PANIC_PARAMS,

src/non_expressive_names.rs

@@ -0,0 +1,150 @@
+use rustc::lint::*;
+use syntax::codemap::Span;
+use syntax::parse::token::InternedString;
+use syntax::ast::*;
+use syntax::visit::{self, FnKind};
+use utils::{span_note_and_lint, in_macro};
+use strsim::levenshtein;
+
+/// **What it does:** This lint warns about names that are very similar and thus confusing
+///
+/// **Why is this bad?** It's hard to distinguish between names that differ only by a single character
+///
+/// **Known problems:** None?
+///
+/// **Example:** `checked_exp` and `checked_expr`
+declare_lint! {
+    pub SIMILAR_NAMES,
+    Warn,
+    "similarly named items and bindings"
+}
+
+pub struct SimilarNames(pub usize);
+
+impl LintPass for SimilarNames {
+    fn get_lints(&self) -> LintArray {
+        lint_array!(SIMILAR_NAMES)
+    }
+}
+
+struct SimilarNamesLocalVisitor<'a, 'b: 'a> {
+    names: Vec<(InternedString, Span)>,
+    cx: &'a EarlyContext<'b>,
+    limit: usize,
+}
+
+const WHITELIST: &'static [&'static str] = &[
+    "lhs", "rhs",
+];
+
+struct SimilarNamesNameVisitor<'a, 'b: 'a, 'c: 'b>(&'a mut SimilarNamesLocalVisitor<'b, 'c>);
+
+impl<'v, 'a, 'b, 'c> visit::Visitor<'v> for SimilarNamesNameVisitor<'a, 'b, 'c> {
+    fn visit_pat(&mut self, pat: &'v Pat) {
+        if let PatKind::Ident(_, id, _) = pat.node {
+            self.check_name(id.span, id.node.name);
+        }
+        visit::walk_pat(self, pat);
+    }
+}
+
+impl<'a, 'b, 'c> SimilarNamesNameVisitor<'a, 'b, 'c> {
+    fn check_name(&mut self, span: Span, name: Name) {
+        if in_macro(self.0.cx, span) {
+            return;
+        }
+        let interned_name = name.as_str();
+        if interned_name.chars().any(char::is_uppercase) {
+            return;
+        }
+        if interned_name.chars().count() < 3 {
+            return;
+        }
+        for &allow in WHITELIST {
+            if interned_name == allow {
+                return;
+            }
+            if interned_name.len() <= allow.len() {
+                continue;
+            }
+            // allow_*
+            let allow_start = allow.chars().chain(Some('_'));
+            if interned_name.chars().zip(allow_start).all(|(l, r)| l == r) {
+                return;
+            }
+            // *_allow
+            let allow_end = Some('_').into_iter().chain(allow.chars());
+            if interned_name.chars().rev().zip(allow_end.rev()).all(|(l, r)| l == r) {
+                return;
+            }
+        }
+        for &(ref existing_name, sp) in &self.0.names {
+            let dist = levenshtein(&interned_name, &existing_name);
+            // equality is caught by shadow lints
+            if dist == 0 {
+                continue;
+            }
+            // if they differ enough it's all good
+            if dist > self.0.limit {
+                continue;
+            }
+            // are we doing stuff like `for item in items`?
+            if interned_name.starts_with(&**existing_name) ||
+               existing_name.starts_with(&*interned_name) ||
+               interned_name.ends_with(&**existing_name) ||
+               existing_name.ends_with(&*interned_name) {
+                continue;
+            }
+            if dist == 1 {
+                // are we doing stuff like a_bar, b_bar, c_bar?
+                if interned_name.chars().next() != existing_name.chars().next() && interned_name.chars().nth(1) == Some('_') {
+                    continue;
+                }
+                // are we doing stuff like foo_x, foo_y, foo_z?
+                if interned_name.chars().rev().next() != existing_name.chars().rev().next() && interned_name.chars().rev().nth(1) == Some('_') {
+                    continue;
+                }
+            }
+            span_note_and_lint(self.0.cx, SIMILAR_NAMES, span, "binding's name is too similar to existing binding", sp, "existing binding defined here");
+            return;
+        }
+        self.0.names.push((interned_name, span));
+    }
+}
+
+impl<'v, 'a, 'b> visit::Visitor<'v> for SimilarNamesLocalVisitor<'a, 'b> {
+    fn visit_local(&mut self, local: &'v Local) {
+        SimilarNamesNameVisitor(self).visit_local(local)
+    }
+    fn visit_block(&mut self, blk: &'v Block) {
+        // ensure scoping rules work
+        let n = self.names.len();
+        visit::walk_block(self, blk);
+        self.names.truncate(n);
+    }
+    fn visit_arm(&mut self, arm: &'v Arm) {
+        let n = self.names.len();
+        // just go through the first pattern, as either all patterns bind the same bindings or rustc would have errored much earlier
+        SimilarNamesNameVisitor(self).visit_pat(&arm.pats[0]);
+        self.names.truncate(n);
+    }
+    fn visit_item(&mut self, _: &'v Item) {
+        // do nothing
+    }
+}
+
+impl EarlyLintPass for SimilarNames {
+    fn check_fn(&mut self, cx: &EarlyContext, _: FnKind, decl: &FnDecl, blk: &Block, _: Span, _: NodeId) {
+        let mut visitor = SimilarNamesLocalVisitor {
+            names: Vec::new(),
+            cx: cx,
+            limit: self.0,
+        };
+        // initialize with function arguments
+        for arg in &decl.inputs {
+            visit::walk_pat(&mut SimilarNamesNameVisitor(&mut visitor), &arg.pat);
+        }
+        // walk all other bindings
+        visit::walk_block(&mut visitor, blk);
+    }
+}

src/types.rs

@@ -638,7 +638,7 @@ fn detect_absurd_comparison<'a>(cx: &LateContext, op: BinOp_, lhs: &'a Expr, rhs
         Lt,
         Le,
     };
-    let (rel, lhs2, rhs2) = match op {
+    let (rel, normalized_lhs, normalized_rhs) = match op {
         BiLt => (Rel::Lt, lhs, rhs),
         BiLe => (Rel::Le, lhs, rhs),
         BiGt => (Rel::Lt, rhs, lhs),
@@ -646,8 +646,8 @@ fn detect_absurd_comparison<'a>(cx: &LateContext, op: BinOp_, lhs: &'a Expr, rhs
         _ => return None,
     };
 
-    let lx = detect_extreme_expr(cx, lhs2);
-    let rx = detect_extreme_expr(cx, rhs2);
+    let lx = detect_extreme_expr(cx, normalized_lhs);
+    let rx = detect_extreme_expr(cx, normalized_rhs);
 
     Some(match rel {
         Rel::Lt => {

src/utils/hir.rs

@@ -67,24 +67,24 @@ impl<'a, 'tcx: 'a> SpanlessEq<'a, 'tcx> {
         }
 
         match (&left.node, &right.node) {
-            (&ExprAddrOf(lmut, ref le), &ExprAddrOf(rmut, ref re)) => lmut == rmut && self.eq_expr(le, re),
+            (&ExprAddrOf(l_mut, ref le), &ExprAddrOf(r_mut, ref re)) => l_mut == r_mut && self.eq_expr(le, re),
             (&ExprAgain(li), &ExprAgain(ri)) => both(&li, &ri, |l, r| l.node.name.as_str() == r.node.name.as_str()),
             (&ExprAssign(ref ll, ref lr), &ExprAssign(ref rl, ref rr)) => self.eq_expr(ll, rl) && self.eq_expr(lr, rr),
             (&ExprAssignOp(ref lo, ref ll, ref lr), &ExprAssignOp(ref ro, ref rl, ref rr)) => {
                 lo.node == ro.node && self.eq_expr(ll, rl) && self.eq_expr(lr, rr)
             }
             (&ExprBlock(ref l), &ExprBlock(ref r)) => self.eq_block(l, r),
-            (&ExprBinary(lop, ref ll, ref lr), &ExprBinary(rop, ref rl, ref rr)) => {
-                lop.node == rop.node && self.eq_expr(ll, rl) && self.eq_expr(lr, rr)
+            (&ExprBinary(l_op, ref ll, ref lr), &ExprBinary(r_op, ref rl, ref rr)) => {
+                l_op.node == r_op.node && self.eq_expr(ll, rl) && self.eq_expr(lr, rr)
             }
             (&ExprBreak(li), &ExprBreak(ri)) => both(&li, &ri, |l, r| l.node.name.as_str() == r.node.name.as_str()),
             (&ExprBox(ref l), &ExprBox(ref r)) => self.eq_expr(l, r),
-            (&ExprCall(ref lfun, ref largs), &ExprCall(ref rfun, ref rargs)) => {
-                !self.ignore_fn && self.eq_expr(lfun, rfun) && self.eq_exprs(largs, rargs)
+            (&ExprCall(ref l_fun, ref l_args), &ExprCall(ref r_fun, ref r_args)) => {
+                !self.ignore_fn && self.eq_expr(l_fun, r_fun) && self.eq_exprs(l_args, r_args)
             }
             (&ExprCast(ref lx, ref lt), &ExprCast(ref rx, ref rt)) => self.eq_expr(lx, rx) && self.eq_ty(lt, rt),
-            (&ExprField(ref lfexp, ref lfident), &ExprField(ref rfexp, ref rfident)) => {
-                lfident.node == rfident.node && self.eq_expr(lfexp, rfexp)
+            (&ExprField(ref l_f_exp, ref l_f_ident), &ExprField(ref r_f_exp, ref r_f_ident)) => {
+                l_f_ident.node == r_f_ident.node && self.eq_expr(l_f_exp, r_f_exp)
             }
             (&ExprIndex(ref la, ref li), &ExprIndex(ref ra, ref ri)) => self.eq_expr(la, ra) && self.eq_expr(li, ri),
             (&ExprIf(ref lc, ref lt, ref le), &ExprIf(ref rc, ref rt, ref re)) => {
@@ -101,25 +101,25 @@ impl<'a, 'tcx: 'a> SpanlessEq<'a, 'tcx> {
                     over(&l.pats, &r.pats, |l, r| self.eq_pat(l, r))
                 })
             }
-            (&ExprMethodCall(ref lname, ref ltys, ref largs),
-             &ExprMethodCall(ref rname, ref rtys, ref rargs)) => {
+            (&ExprMethodCall(ref l_name, ref l_tys, ref l_args),
+             &ExprMethodCall(ref r_name, ref r_tys, ref r_args)) => {
                 // TODO: tys
-                !self.ignore_fn && lname.node == rname.node && ltys.is_empty() && rtys.is_empty() &&
-                self.eq_exprs(largs, rargs)
+                !self.ignore_fn && l_name.node == r_name.node && l_tys.is_empty() && r_tys.is_empty() &&
+                self.eq_exprs(l_args, r_args)
             }
             (&ExprRepeat(ref le, ref ll), &ExprRepeat(ref re, ref rl)) => self.eq_expr(le, re) && self.eq_expr(ll, rl),
             (&ExprRet(ref l), &ExprRet(ref r)) => both(l, r, |l, r| self.eq_expr(l, r)),
-            (&ExprPath(ref lqself, ref lsubpath), &ExprPath(ref rqself, ref rsubpath)) => {
-                both(lqself, rqself, |l, r| self.eq_qself(l, r)) && self.eq_path(lsubpath, rsubpath)
+            (&ExprPath(ref l_qself, ref l_subpath), &ExprPath(ref r_qself, ref r_subpath)) => {
+                both(l_qself, r_qself, |l, r| self.eq_qself(l, r)) && self.eq_path(l_subpath, r_subpath)
             }
-            (&ExprStruct(ref lpath, ref lf, ref lo), &ExprStruct(ref rpath, ref rf, ref ro)) => {
-                self.eq_path(lpath, rpath) &&
+            (&ExprStruct(ref l_path, ref lf, ref lo), &ExprStruct(ref r_path, ref rf, ref ro)) => {
+                self.eq_path(l_path, r_path) &&
                     both(lo, ro, |l, r| self.eq_expr(l, r)) &&
                     over(lf, rf, |l, r| self.eq_field(l, r))
             }
-            (&ExprTup(ref ltup), &ExprTup(ref rtup)) => self.eq_exprs(ltup, rtup),
+            (&ExprTup(ref l_tup), &ExprTup(ref r_tup)) => self.eq_exprs(l_tup, r_tup),
             (&ExprTupField(ref le, li), &ExprTupField(ref re, ri)) => li.node == ri.node && self.eq_expr(le, re),
-            (&ExprUnary(lop, ref le), &ExprUnary(rop, ref re)) => lop == rop && self.eq_expr(le, re),
+            (&ExprUnary(l_op, ref le), &ExprUnary(r_op, ref re)) => l_op == r_op && self.eq_expr(le, re),
             (&ExprVec(ref l), &ExprVec(ref r)) => self.eq_exprs(l, r),
             (&ExprWhile(ref lc, ref lb, ref ll), &ExprWhile(ref rc, ref rb, ref rl)) => {
                 self.eq_expr(lc, rc) && self.eq_block(lb, rb) && both(ll, rl, |l, r| l.name.as_str() == r.name.as_str())
@@ -179,16 +179,16 @@ impl<'a, 'tcx: 'a> SpanlessEq<'a, 'tcx> {
 
     fn eq_ty(&self, left: &Ty, right: &Ty) -> bool {
         match (&left.node, &right.node) {
-            (&TyVec(ref lvec), &TyVec(ref rvec)) => self.eq_ty(lvec, rvec),
+            (&TyVec(ref l_vec), &TyVec(ref r_vec)) => self.eq_ty(l_vec, r_vec),
             (&TyFixedLengthVec(ref lt, ref ll), &TyFixedLengthVec(ref rt, ref rl)) => {
                 self.eq_ty(lt, rt) && self.eq_expr(ll, rl)
             }
-            (&TyPtr(ref lmut), &TyPtr(ref rmut)) => lmut.mutbl == rmut.mutbl && self.eq_ty(&*lmut.ty, &*rmut.ty),
-            (&TyRptr(_, ref lrmut), &TyRptr(_, ref rrmut)) => {
-                lrmut.mutbl == rrmut.mutbl && self.eq_ty(&*lrmut.ty, &*rrmut.ty)
+            (&TyPtr(ref l_mut), &TyPtr(ref r_mut)) => l_mut.mutbl == r_mut.mutbl && self.eq_ty(&*l_mut.ty, &*r_mut.ty),
+            (&TyRptr(_, ref l_rmut), &TyRptr(_, ref r_rmut)) => {
+                l_rmut.mutbl == r_rmut.mutbl && self.eq_ty(&*l_rmut.ty, &*r_rmut.ty)
             }
-            (&TyPath(ref lq, ref lpath), &TyPath(ref rq, ref rpath)) => {
-                both(lq, rq, |l, r| self.eq_qself(l, r)) && self.eq_path(lpath, rpath)
+            (&TyPath(ref lq, ref l_path), &TyPath(ref rq, ref r_path)) => {
+                both(lq, rq, |l, r| self.eq_qself(l, r)) && self.eq_path(l_path, r_path)
             }
             (&TyTup(ref l), &TyTup(ref r)) => over(l, r, |l, r| self.eq_ty(l, r)),
             (&TyInfer, &TyInfer) => true,

src/utils/mod.rs

@@ -102,8 +102,8 @@ macro_rules! if_let_chain {
 
 /// Returns true if the two spans come from differing expansions (i.e. one is from a macro and one
 /// isn't).
-pub fn differing_macro_contexts(sp1: Span, sp2: Span) -> bool {
-    sp1.expn_id != sp2.expn_id
+pub fn differing_macro_contexts(lhs: Span, rhs: Span) -> bool {
+    rhs.expn_id != lhs.expn_id
 }
 /// Returns true if this `expn_info` was expanded by any macro.
 pub fn in_macro<T: LintContext>(cx: &T, span: Span) -> bool {