From b393752814e55726932a281249e5380643685986 Mon Sep 17 00:00:00 2001
From: llogiq <bogusandre@gmail.com>
Date: Wed, 5 Aug 2015 15:10:45 +0200
Subject: [PATCH] New string_add_assign lint (first part of #121), also
formatting & refactoring
---
README.md | 1 +
src/eq_op.rs | 277 +++++++++++++++++-----------------
src/lib.rs | 3 +
src/strings.rs | 55 +++++++
src/utils.rs | 2 +-
tests/compile-fail/strings.rs | 12 ++
6 files changed, 210 insertions(+), 140 deletions(-)
create mode 100644 src/strings.rs
create mode 100644 tests/compile-fail/strings.rs
diff --git a/README.md b/README.md
index 87339f46464..fcd8d38a3b3 100644
--- a/README.md
+++ b/README.md
@@ -29,6 +29,7 @@ Lints included in this crate:
- `inline_always`: Warns on `#[inline(always)]`, because in most cases it is a bad idea
- `collapsible_if`: Warns on cases where two nested `if`-expressions can be collapsed into one, e.g. `if x { if y { foo() } }` can be written as `if x && y { foo() }`
- `zero_width_space`: Warns on encountering a unicode zero-width space
+ - `string_add_assign`: Warns on `x = x + ..` where `x` is a `String` and suggests using `push_str(..)` instead.
To use, add the following lines to your Cargo.toml:
diff --git a/src/eq_op.rs b/src/eq_op.rs
index bd9787bd51c..1000d310e39 100644
--- a/src/eq_op.rs
+++ b/src/eq_op.rs
@@ -23,238 +23,237 @@ impl LintPass for EqOp {
if let ExprBinary(ref op, ref left, ref right) = e.node {
if is_cmp_or_bit(op) && is_exp_equal(left, right) {
span_lint(cx, EQ_OP, e.span, &format!(
- "equal expressions as operands to {}",
- ast_util::binop_to_string(op.node)));
+ "equal expressions as operands to {}",
+ ast_util::binop_to_string(op.node)));
}
}
}
}
-fn is_exp_equal(left : &Expr, right : &Expr) -> bool {
- match (&left.node, &right.node) {
- (&ExprBinary(ref lop, ref ll, ref lr),
- &ExprBinary(ref rop, ref rl, ref rr)) =>
- lop.node == rop.node &&
- is_exp_equal(ll, rl) && is_exp_equal(lr, rr),
- (&ExprBox(ref lpl, ref lbox), &ExprBox(ref rpl, ref rbox)) =>
- both(lpl, rpl, |l, r| is_exp_equal(l, r)) &&
- is_exp_equal(lbox, rbox),
- (&ExprCall(ref lcallee, ref largs),
- &ExprCall(ref rcallee, ref rargs)) => is_exp_equal(lcallee,
- rcallee) && is_exps_equal(largs, rargs),
- (&ExprCast(ref lc, ref lty), &ExprCast(ref rc, ref rty)) =>
- is_ty_equal(lty, rty) && is_exp_equal(lc, rc),
- (&ExprField(ref lfexp, ref lfident),
- &ExprField(ref rfexp, ref rfident)) =>
- lfident.node == rfident.node && is_exp_equal(lfexp, rfexp),
- (&ExprLit(ref l), &ExprLit(ref r)) => l.node == r.node,
- (&ExprMethodCall(ref lident, ref lcty, ref lmargs),
- &ExprMethodCall(ref rident, ref rcty, ref rmargs)) =>
- lident.node == rident.node && is_tys_equal(lcty, rcty) &&
- is_exps_equal(lmargs, rmargs),
- (&ExprParen(ref lparen), _) => is_exp_equal(lparen, right),
- (_, &ExprParen(ref rparen)) => is_exp_equal(left, rparen),
- (&ExprPath(ref lqself, ref lsubpath),
- &ExprPath(ref rqself, ref rsubpath)) =>
- both(lqself, rqself, |l, r| is_qself_equal(l, r)) &&
- is_path_equal(lsubpath, rsubpath),
- (&ExprTup(ref ltup), &ExprTup(ref rtup)) =>
- is_exps_equal(ltup, rtup),
- (&ExprUnary(lunop, ref l), &ExprUnary(runop, ref r)) =>
- lunop == runop && is_exp_equal(l, r),
- (&ExprVec(ref l), &ExprVec(ref r)) => is_exps_equal(l, r),
- _ => false
- }
+pub fn is_exp_equal(left : &Expr, right : &Expr) -> bool {
+ match (&left.node, &right.node) {
+ (&ExprBinary(ref lop, ref ll, ref lr),
+ &ExprBinary(ref rop, ref rl, ref rr)) =>
+ lop.node == rop.node &&
+ is_exp_equal(ll, rl) && is_exp_equal(lr, rr),
+ (&ExprBox(ref lpl, ref lbox), &ExprBox(ref rpl, ref rbox)) =>
+ both(lpl, rpl, |l, r| is_exp_equal(l, r)) &&
+ is_exp_equal(lbox, rbox),
+ (&ExprCall(ref lcallee, ref largs),
+ &ExprCall(ref rcallee, ref rargs)) => is_exp_equal(lcallee,
+ rcallee) && is_exps_equal(largs, rargs),
+ (&ExprCast(ref lc, ref lty), &ExprCast(ref rc, ref rty)) =>
+ is_ty_equal(lty, rty) && is_exp_equal(lc, rc),
+ (&ExprField(ref lfexp, ref lfident),
+ &ExprField(ref rfexp, ref rfident)) =>
+ lfident.node == rfident.node && is_exp_equal(lfexp, rfexp),
+ (&ExprLit(ref l), &ExprLit(ref r)) => l.node == r.node,
+ (&ExprMethodCall(ref lident, ref lcty, ref lmargs),
+ &ExprMethodCall(ref rident, ref rcty, ref rmargs)) =>
+ lident.node == rident.node && is_tys_equal(lcty, rcty) &&
+ is_exps_equal(lmargs, rmargs),
+ (&ExprParen(ref lparen), _) => is_exp_equal(lparen, right),
+ (_, &ExprParen(ref rparen)) => is_exp_equal(left, rparen),
+ (&ExprPath(ref lqself, ref lsubpath),
+ &ExprPath(ref rqself, ref rsubpath)) =>
+ both(lqself, rqself, |l, r| is_qself_equal(l, r)) &&
+ is_path_equal(lsubpath, rsubpath),
+ (&ExprTup(ref ltup), &ExprTup(ref rtup)) =>
+ is_exps_equal(ltup, rtup),
+ (&ExprUnary(lunop, ref l), &ExprUnary(runop, ref r)) =>
+ lunop == runop && is_exp_equal(l, r),
+ (&ExprVec(ref l), &ExprVec(ref r)) => is_exps_equal(l, r),
+ _ => false
+ }
}
fn is_exps_equal(left : &[P<Expr>], right : &[P<Expr>]) -> bool {
- over(left, right, |l, r| is_exp_equal(l, r))
+ over(left, right, |l, r| is_exp_equal(l, r))
}
fn is_path_equal(left : &Path, right : &Path) -> bool {
// The == of idents doesn't work with different contexts,
- // we have to be explicit about hygeine
- left.global == right.global
- && left.segments.iter().zip(right.segments.iter())
- .all( |(l,r)| l.identifier.name == r.identifier.name
- && l.identifier.ctxt == r.identifier.ctxt
- && l.parameters == r.parameters)
+ // we have to be explicit about hygiene
+ left.global == right.global && over(&left.segments, &right.segments,
+ |l, r| l.identifier.name == r.identifier.name
+ && l.identifier.ctxt == r.identifier.ctxt
+ && l.parameters == r.parameters)
}
fn is_qself_equal(left : &QSelf, right : &QSelf) -> bool {
- left.ty.node == right.ty.node && left.position == right.position
+ left.ty.node == right.ty.node && left.position == right.position
}
fn is_ty_equal(left : &Ty, right : &Ty) -> bool {
- match (&left.node, &right.node) {
- (&TyVec(ref lvec), &TyVec(ref rvec)) => is_ty_equal(lvec, rvec),
- (&TyFixedLengthVec(ref lfvty, ref lfvexp),
- &TyFixedLengthVec(ref rfvty, ref rfvexp)) =>
- is_ty_equal(lfvty, rfvty) && is_exp_equal(lfvexp, rfvexp),
- (&TyPtr(ref lmut), &TyPtr(ref rmut)) => is_mut_ty_equal(lmut, rmut),
- (&TyRptr(ref ltime, ref lrmut), &TyRptr(ref rtime, ref rrmut)) =>
- both(ltime, rtime, is_lifetime_equal) &&
- is_mut_ty_equal(lrmut, rrmut),
- (&TyBareFn(ref lbare), &TyBareFn(ref rbare)) =>
- is_bare_fn_ty_equal(lbare, rbare),
+ match (&left.node, &right.node) {
+ (&TyVec(ref lvec), &TyVec(ref rvec)) => is_ty_equal(lvec, rvec),
+ (&TyFixedLengthVec(ref lfvty, ref lfvexp),
+ &TyFixedLengthVec(ref rfvty, ref rfvexp)) =>
+ is_ty_equal(lfvty, rfvty) && is_exp_equal(lfvexp, rfvexp),
+ (&TyPtr(ref lmut), &TyPtr(ref rmut)) => is_mut_ty_equal(lmut, rmut),
+ (&TyRptr(ref ltime, ref lrmut), &TyRptr(ref rtime, ref rrmut)) =>
+ both(ltime, rtime, is_lifetime_equal) &&
+ is_mut_ty_equal(lrmut, rrmut),
+ (&TyBareFn(ref lbare), &TyBareFn(ref rbare)) =>
+ is_bare_fn_ty_equal(lbare, rbare),
(&TyTup(ref ltup), &TyTup(ref rtup)) => is_tys_equal(ltup, rtup),
- (&TyPath(ref lq, ref lpath), &TyPath(ref rq, ref rpath)) =>
- both(lq, rq, is_qself_equal) && is_path_equal(lpath, rpath),
+ (&TyPath(ref lq, ref lpath), &TyPath(ref rq, ref rpath)) =>
+ both(lq, rq, is_qself_equal) && is_path_equal(lpath, rpath),
(&TyObjectSum(ref lsumty, ref lobounds),
- &TyObjectSum(ref rsumty, ref robounds)) =>
- is_ty_equal(lsumty, rsumty) &&
- is_param_bounds_equal(lobounds, robounds),
- (&TyPolyTraitRef(ref ltbounds), &TyPolyTraitRef(ref rtbounds)) =>
- is_param_bounds_equal(ltbounds, rtbounds),
+ &TyObjectSum(ref rsumty, ref robounds)) =>
+ is_ty_equal(lsumty, rsumty) &&
+ is_param_bounds_equal(lobounds, robounds),
+ (&TyPolyTraitRef(ref ltbounds), &TyPolyTraitRef(ref rtbounds)) =>
+ is_param_bounds_equal(ltbounds, rtbounds),
(&TyParen(ref lty), &TyParen(ref rty)) => is_ty_equal(lty, rty),
(&TyTypeof(ref lof), &TyTypeof(ref rof)) => is_exp_equal(lof, rof),
- (&TyInfer, &TyInfer) => true,
- _ => false
- }
+ (&TyInfer, &TyInfer) => true,
+ _ => false
+ }
}
fn is_param_bound_equal(left : &TyParamBound, right : &TyParamBound)
- -> bool {
- match(left, right) {
- (&TraitTyParamBound(ref lpoly, ref lmod),
- &TraitTyParamBound(ref rpoly, ref rmod)) =>
- lmod == rmod && is_poly_traitref_equal(lpoly, rpoly),
+ -> bool {
+ match(left, right) {
+ (&TraitTyParamBound(ref lpoly, ref lmod),
+ &TraitTyParamBound(ref rpoly, ref rmod)) =>
+ lmod == rmod && is_poly_traitref_equal(lpoly, rpoly),
(&RegionTyParamBound(ref ltime), &RegionTyParamBound(ref rtime)) =>
- is_lifetime_equal(ltime, rtime),
+ is_lifetime_equal(ltime, rtime),
_ => false
- }
+ }
}
fn is_poly_traitref_equal(left : &PolyTraitRef, right : &PolyTraitRef)
- -> bool {
- is_lifetimedefs_equal(&left.bound_lifetimes, &right.bound_lifetimes)
- && is_path_equal(&left.trait_ref.path, &right.trait_ref.path)
+ -> bool {
+ is_lifetimedefs_equal(&left.bound_lifetimes, &right.bound_lifetimes)
+ && is_path_equal(&left.trait_ref.path, &right.trait_ref.path)
}
fn is_param_bounds_equal(left : &TyParamBounds, right : &TyParamBounds)
- -> bool {
- over(left, right, is_param_bound_equal)
+ -> bool {
+ over(left, right, is_param_bound_equal)
}
fn is_mut_ty_equal(left : &MutTy, right : &MutTy) -> bool {
- left.mutbl == right.mutbl && is_ty_equal(&left.ty, &right.ty)
+ left.mutbl == right.mutbl && is_ty_equal(&left.ty, &right.ty)
}
fn is_bare_fn_ty_equal(left : &BareFnTy, right : &BareFnTy) -> bool {
- left.unsafety == right.unsafety && left.abi == right.abi &&
- is_lifetimedefs_equal(&left.lifetimes, &right.lifetimes) &&
- is_fndecl_equal(&left.decl, &right.decl)
+ left.unsafety == right.unsafety && left.abi == right.abi &&
+ is_lifetimedefs_equal(&left.lifetimes, &right.lifetimes) &&
+ is_fndecl_equal(&left.decl, &right.decl)
}
fn is_fndecl_equal(left : &P<FnDecl>, right : &P<FnDecl>) -> bool {
- left.variadic == right.variadic &&
- is_args_equal(&left.inputs, &right.inputs) &&
- is_fnret_ty_equal(&left.output, &right.output)
+ left.variadic == right.variadic &&
+ is_args_equal(&left.inputs, &right.inputs) &&
+ is_fnret_ty_equal(&left.output, &right.output)
}
fn is_fnret_ty_equal(left : &FunctionRetTy, right : &FunctionRetTy)
- -> bool {
- match (left, right) {
- (&NoReturn(_), &NoReturn(_)) |
- (&DefaultReturn(_), &DefaultReturn(_)) => true,
- (&Return(ref lty), &Return(ref rty)) => is_ty_equal(lty, rty),
- _ => false
- }
+ -> bool {
+ match (left, right) {
+ (&NoReturn(_), &NoReturn(_)) |
+ (&DefaultReturn(_), &DefaultReturn(_)) => true,
+ (&Return(ref lty), &Return(ref rty)) => is_ty_equal(lty, rty),
+ _ => false
+ }
}
fn is_arg_equal(l: &Arg, r : &Arg) -> bool {
- is_ty_equal(&l.ty, &r.ty) && is_pat_equal(&l.pat, &r.pat)
+ is_ty_equal(&l.ty, &r.ty) && is_pat_equal(&l.pat, &r.pat)
}
fn is_args_equal(left : &[Arg], right : &[Arg]) -> bool {
- over(left, right, is_arg_equal)
+ over(left, right, is_arg_equal)
}
fn is_pat_equal(left : &Pat, right : &Pat) -> bool {
- match(&left.node, &right.node) {
- (&PatWild(lwild), &PatWild(rwild)) => lwild == rwild,
- (&PatIdent(ref lmode, ref lident, Option::None),
- &PatIdent(ref rmode, ref rident, Option::None)) =>
- lmode == rmode && is_ident_equal(&lident.node, &rident.node),
- (&PatIdent(ref lmode, ref lident, Option::Some(ref lpat)),
- &PatIdent(ref rmode, ref rident, Option::Some(ref rpat))) =>
- lmode == rmode && is_ident_equal(&lident.node, &rident.node) &&
- is_pat_equal(lpat, rpat),
+ match(&left.node, &right.node) {
+ (&PatWild(lwild), &PatWild(rwild)) => lwild == rwild,
+ (&PatIdent(ref lmode, ref lident, Option::None),
+ &PatIdent(ref rmode, ref rident, Option::None)) =>
+ lmode == rmode && is_ident_equal(&lident.node, &rident.node),
+ (&PatIdent(ref lmode, ref lident, Option::Some(ref lpat)),
+ &PatIdent(ref rmode, ref rident, Option::Some(ref rpat))) =>
+ lmode == rmode && is_ident_equal(&lident.node, &rident.node) &&
+ is_pat_equal(lpat, rpat),
(&PatEnum(ref lpath, ref lenum), &PatEnum(ref rpath, ref renum)) =>
- is_path_equal(lpath, rpath) && both(lenum, renum, |l, r|
- is_pats_equal(l, r)),
+ is_path_equal(lpath, rpath) && both(lenum, renum, |l, r|
+ is_pats_equal(l, r)),
(&PatStruct(ref lpath, ref lfieldpat, lbool),
- &PatStruct(ref rpath, ref rfieldpat, rbool)) =>
- lbool == rbool && is_path_equal(lpath, rpath) &&
- is_spanned_fieldpats_equal(lfieldpat, rfieldpat),
+ &PatStruct(ref rpath, ref rfieldpat, rbool)) =>
+ lbool == rbool && is_path_equal(lpath, rpath) &&
+ is_spanned_fieldpats_equal(lfieldpat, rfieldpat),
(&PatTup(ref ltup), &PatTup(ref rtup)) => is_pats_equal(ltup, rtup),
(&PatBox(ref lboxed), &PatBox(ref rboxed)) =>
- is_pat_equal(lboxed, rboxed),
+ is_pat_equal(lboxed, rboxed),
(&PatRegion(ref lpat, ref lmut), &PatRegion(ref rpat, ref rmut)) =>
- is_pat_equal(lpat, rpat) && lmut == rmut,
- (&PatLit(ref llit), &PatLit(ref rlit)) => is_exp_equal(llit, rlit),
+ is_pat_equal(lpat, rpat) && lmut == rmut,
+ (&PatLit(ref llit), &PatLit(ref rlit)) => is_exp_equal(llit, rlit),
(&PatRange(ref lfrom, ref lto), &PatRange(ref rfrom, ref rto)) =>
- is_exp_equal(lfrom, rfrom) && is_exp_equal(lto, rto),
+ is_exp_equal(lfrom, rfrom) && is_exp_equal(lto, rto),
(&PatVec(ref lfirst, Option::None, ref llast),
- &PatVec(ref rfirst, Option::None, ref rlast)) =>
- is_pats_equal(lfirst, rfirst) && is_pats_equal(llast, rlast),
+ &PatVec(ref rfirst, Option::None, ref rlast)) =>
+ is_pats_equal(lfirst, rfirst) && is_pats_equal(llast, rlast),
(&PatVec(ref lfirst, Option::Some(ref lpat), ref llast),
- &PatVec(ref rfirst, Option::Some(ref rpat), ref rlast)) =>
- is_pats_equal(lfirst, rfirst) && is_pat_equal(lpat, rpat) &&
- is_pats_equal(llast, rlast),
- // I don't match macros for now, the code is slow enough as is ;-)
- _ => false
- }
+ &PatVec(ref rfirst, Option::Some(ref rpat), ref rlast)) =>
+ is_pats_equal(lfirst, rfirst) && is_pat_equal(lpat, rpat) &&
+ is_pats_equal(llast, rlast),
+ // I don't match macros for now, the code is slow enough as is ;-)
+ _ => false
+ }
}
fn is_spanned_fieldpats_equal(left : &[code::Spanned<FieldPat>],
- right : &[code::Spanned<FieldPat>]) -> bool {
- over(left, right, |l, r| is_fieldpat_equal(&l.node, &r.node))
+ right : &[code::Spanned<FieldPat>]) -> bool {
+ over(left, right, |l, r| is_fieldpat_equal(&l.node, &r.node))
}
fn is_fieldpat_equal(left : &FieldPat, right : &FieldPat) -> bool {
- left.is_shorthand == right.is_shorthand &&
- is_ident_equal(&left.ident, &right.ident) &&
- is_pat_equal(&left.pat, &right.pat)
+ left.is_shorthand == right.is_shorthand &&
+ is_ident_equal(&left.ident, &right.ident) &&
+ is_pat_equal(&left.pat, &right.pat)
}
fn is_ident_equal(left : &Ident, right : &Ident) -> bool {
- &left.name == &right.name && left.ctxt == right.ctxt
+ &left.name == &right.name && left.ctxt == right.ctxt
}
fn is_pats_equal(left : &[P<Pat>], right : &[P<Pat>]) -> bool {
- over(left, right, |l, r| is_pat_equal(l, r))
+ over(left, right, |l, r| is_pat_equal(l, r))
}
fn is_lifetimedef_equal(left : &LifetimeDef, right : &LifetimeDef)
- -> bool {
- is_lifetime_equal(&left.lifetime, &right.lifetime) &&
- over(&left.bounds, &right.bounds, is_lifetime_equal)
+ -> bool {
+ is_lifetime_equal(&left.lifetime, &right.lifetime) &&
+ over(&left.bounds, &right.bounds, is_lifetime_equal)
}
fn is_lifetimedefs_equal(left : &[LifetimeDef], right : &[LifetimeDef])
- -> bool {
- over(left, right, is_lifetimedef_equal)
+ -> bool {
+ over(left, right, is_lifetimedef_equal)
}
fn is_lifetime_equal(left : &Lifetime, right : &Lifetime) -> bool {
- left.name == right.name
+ left.name == right.name
}
fn is_tys_equal(left : &[P<Ty>], right : &[P<Ty>]) -> bool {
- over(left, right, |l, r| is_ty_equal(l, r))
+ over(left, right, |l, r| is_ty_equal(l, r))
}
fn over<X, F>(left: &[X], right: &[X], mut eq_fn: F) -> bool
- where F: FnMut(&X, &X) -> bool {
+ where F: FnMut(&X, &X) -> bool {
left.len() == right.len() && left.iter().zip(right).all(|(x, y)|
- eq_fn(x, y))
+ eq_fn(x, y))
}
fn both<X, F>(l: &Option<X>, r: &Option<X>, mut eq_fn : F) -> bool
- where F: FnMut(&X, &X) -> bool {
- l.as_ref().map_or_else(|| r.is_none(), |x| r.as_ref().map_or(false,
- |y| eq_fn(x, y)))
+ where F: FnMut(&X, &X) -> bool {
+ l.as_ref().map_or_else(|| r.is_none(), |x| r.as_ref().map_or(false,
+ |y| eq_fn(x, y)))
}
fn is_cmp_or_bit(op : &BinOp) -> bool {
diff --git a/src/lib.rs b/src/lib.rs
index 647128e0f0c..d0d0b637468 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -28,6 +28,7 @@ pub mod attrs;
pub mod collapsible_if;
pub mod unicode;
pub mod utils;
+pub mod strings;
#[plugin_registrar]
pub fn plugin_registrar(reg: &mut Registry) {
@@ -51,6 +52,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
reg.register_lint_pass(box attrs::AttrPass as LintPassObject);
reg.register_lint_pass(box collapsible_if::CollapsibleIf as LintPassObject);
reg.register_lint_pass(box unicode::Unicode as LintPassObject);
+ reg.register_lint_pass(box strings::StringAdd as LintPassObject);
reg.register_lint_group("clippy", vec![types::BOX_VEC, types::LINKEDLIST,
misc::SINGLE_MATCH, misc::STR_TO_STRING,
@@ -70,5 +72,6 @@ pub fn plugin_registrar(reg: &mut Registry) {
attrs::INLINE_ALWAYS,
collapsible_if::COLLAPSIBLE_IF,
unicode::ZERO_WIDTH_SPACE,
+ strings::STRING_ADD_ASSIGN,
]);
}
diff --git a/src/strings.rs b/src/strings.rs
new file mode 100644
index 00000000000..8bd882cada2
--- /dev/null
+++ b/src/strings.rs
@@ -0,0 +1,55 @@
+//! This LintPass catches both string addition and string addition + assignment
+//!
+//! Note that since we have two lints where one subsumes the other, we try to
+//! disable the subsumed lint unless it has a higher level
+
+use rustc::lint::*;
+use rustc::middle::ty::TypeVariants::TyStruct;
+use syntax::ast::*;
+use syntax::codemap::{Span, Spanned};
+use eq_op::is_exp_equal;
+use misc::walk_ty;
+use types::match_ty_unwrap;
+use utils::{match_def_path, span_lint};
+
+declare_lint! {
+ pub STRING_ADD_ASSIGN,
+ Warn,
+ "Warn on `x = x + ..` where x is a `String`"
+}
+
+#[derive(Copy,Clone)]
+pub struct StringAdd;
+
+impl LintPass for StringAdd {
+ fn get_lints(&self) -> LintArray {
+ lint_array!(STRING_ADD_ASSIGN)
+ }
+
+ fn check_expr(&mut self, cx: &Context, e: &Expr) {
+ if let &ExprAssign(ref target, ref src) =&e.node {
+ if is_string(cx, target) && is_add(src, target) {
+ span_lint(cx, STRING_ADD_ASSIGN, e.span,
+ "You assign the result of adding something to this string. \
+ Consider using `String::push_str(..) instead.")
+ }
+ }
+ }
+}
+
+fn is_string(cx: &Context, e: &Expr) -> bool {
+ if let TyStruct(def_id, _) = walk_ty(cx.tcx.expr_ty(e)).sty {
+ match_def_path(cx, def_id, &["std", "string", "String"])
+ } else { false }
+}
+
+fn is_add(src: &Expr, target: &Expr) -> bool {
+ match &src.node {
+ &ExprBinary(Spanned{ node: BiAdd, .. }, ref left, _) =>
+ is_exp_equal(target, left),
+ &ExprBlock(ref block) => block.stmts.is_empty() &&
+ block.expr.as_ref().map_or(false, |expr| is_add(&*expr, target)),
+ &ExprParen(ref expr) => is_add(&*expr, target),
+ _ => false
+ }
+}
diff --git a/src/utils.rs b/src/utils.rs
index d62e082c1fc..4a87f4b3a2e 100644
--- a/src/utils.rs
+++ b/src/utils.rs
@@ -41,7 +41,7 @@ pub fn match_def_path(cx: &Context, def_id: DefId, path: &[&str]) -> bool {
/// `match_path(path, &["std", "rt", "begin_unwind"])`
pub fn match_path(path: &Path, segments: &[&str]) -> bool {
path.segments.iter().rev().zip(segments.iter().rev()).all(
- |(a,b)| a.identifier.name == b)
+ |(a,b)| &a.identifier.name.as_str() == b)
}
/// convert a span to a code snippet if available, otherwise use default, e.g.
diff --git a/tests/compile-fail/strings.rs b/tests/compile-fail/strings.rs
new file mode 100644
index 00000000000..2b200f1d07e
--- /dev/null
+++ b/tests/compile-fail/strings.rs
@@ -0,0 +1,12 @@
+#![feature(plugin)]
+#![plugin(clippy)]
+
+#![deny(string_add_assign)]
+
+fn main() {
+ let x = "".to_owned();
+
+ for i in (1..3) {
+ x = x + "."; //~ERROR
+ }
+}