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Merge pull request #566 from mcarton/starts_with
Add a lint for starts_with
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commit
c570fc6079
@ -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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##Lints
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There are 94 lints included in this crate:
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There are 95 lints included in this crate:
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name | default | meaning
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---------------------------------------------------------------------------------------------------------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
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@ -20,6 +20,7 @@ name
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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_sign_loss](https://github.com/Manishearth/rust-clippy/wiki#cast_sign_loss) | allow | casts from signed types to unsigned types, e.g `x as u32` where `x: i32`
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[chars_next_cmp](https://github.com/Manishearth/rust-clippy/wiki#chars_next_cmp) | warn | using `.chars().next()` to check if a string starts with a char
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[cmp_nan](https://github.com/Manishearth/rust-clippy/wiki#cmp_nan) | deny | comparisons to NAN (which will always return false, which is probably not intended)
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[cmp_owned](https://github.com/Manishearth/rust-clippy/wiki#cmp_owned) | warn | creating owned instances for comparing with others, e.g. `x == "foo".to_string()`
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[collapsible_if](https://github.com/Manishearth/rust-clippy/wiki#collapsible_if) | warn | two nested `if`-expressions can be collapsed into one, e.g. `if x { if y { foo() } }` can be written as `if x && y { foo() }`
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@ -191,6 +191,7 @@ pub fn plugin_registrar(reg: &mut Registry) {
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matches::MATCH_OVERLAPPING_ARM,
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matches::MATCH_REF_PATS,
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matches::SINGLE_MATCH,
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methods::CHARS_NEXT_CMP,
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methods::FILTER_NEXT,
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methods::OK_EXPECT,
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methods::OPTION_MAP_UNWRAP_OR,
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120
src/methods.rs
120
src/methods.rs
@ -7,11 +7,14 @@ use std::borrow::Cow;
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use syntax::ptr::P;
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use syntax::codemap::Span;
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use utils::{snippet, span_lint, span_note_and_lint, match_path, match_type, method_chain_args, match_trait_method,
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walk_ptrs_ty_depth, walk_ptrs_ty, get_trait_def_id, implements_trait};
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use utils::{
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BTREEMAP_ENTRY_PATH, DEFAULT_TRAIT_PATH, HASHMAP_ENTRY_PATH, OPTION_PATH,
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RESULT_PATH, STRING_PATH
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get_trait_def_id, implements_trait, in_external_macro, in_macro, match_path,
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match_trait_method, match_type, method_chain_args, snippet, span_lint, span_lint_and_then,
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span_note_and_lint, walk_ptrs_ty, walk_ptrs_ty_depth,
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};
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use utils::{
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BTREEMAP_ENTRY_PATH, DEFAULT_TRAIT_PATH, HASHMAP_ENTRY_PATH, OPTION_PATH, RESULT_PATH,
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STRING_PATH
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};
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use utils::MethodArgs;
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use rustc::middle::cstore::CrateStore;
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@ -176,6 +179,17 @@ declare_lint!(pub SEARCH_IS_SOME, Warn,
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"using an iterator search followed by `is_some()`, which is more succinctly \
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expressed as a call to `any()`");
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/// **What it does:** This lint `Warn`s on using `.chars().next()` on a `str` to check if it
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/// starts with a given char.
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///
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/// **Why is this bad?** Readability, this can be written more concisely as `_.starts_with(_)`.
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///
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/// **Known problems:** None.
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///
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/// **Example:** `name.chars().next() == Some('_')`
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declare_lint!(pub CHARS_NEXT_CMP, Warn,
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"using `.chars().next()` to check if a string starts with a char");
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/// **What it does:** This lint checks for calls to `.or(foo(..))`, `.unwrap_or(foo(..))`, etc., and
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/// suggests to use `or_else`, `unwrap_or_else`, etc., or `unwrap_or_default` instead.
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///
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@ -210,39 +224,56 @@ impl LintPass for MethodsPass {
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OK_EXPECT,
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OPTION_MAP_UNWRAP_OR,
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OPTION_MAP_UNWRAP_OR_ELSE,
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OR_FUN_CALL)
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OR_FUN_CALL,
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CHARS_NEXT_CMP)
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}
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}
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impl LateLintPass for MethodsPass {
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fn check_expr(&mut self, cx: &LateContext, expr: &Expr) {
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if let ExprMethodCall(name, _, ref args) = expr.node {
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// Chain calls
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if let Some(arglists) = method_chain_args(expr, &["unwrap"]) {
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lint_unwrap(cx, expr, arglists[0]);
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} else if let Some(arglists) = method_chain_args(expr, &["to_string"]) {
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lint_to_string(cx, expr, arglists[0]);
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} else if let Some(arglists) = method_chain_args(expr, &["ok", "expect"]) {
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lint_ok_expect(cx, expr, arglists[0]);
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} else if let Some(arglists) = method_chain_args(expr, &["map", "unwrap_or"]) {
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lint_map_unwrap_or(cx, expr, arglists[0], arglists[1]);
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} else if let Some(arglists) = method_chain_args(expr, &["map", "unwrap_or_else"]) {
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lint_map_unwrap_or_else(cx, expr, arglists[0], arglists[1]);
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} else if let Some(arglists) = method_chain_args(expr, &["filter", "next"]) {
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lint_filter_next(cx, expr, arglists[0]);
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} else if let Some(arglists) = method_chain_args(expr, &["find", "is_some"]) {
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lint_search_is_some(cx, expr, "find", arglists[0], arglists[1]);
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} else if let Some(arglists) = method_chain_args(expr, &["position", "is_some"]) {
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lint_search_is_some(cx, expr, "position", arglists[0], arglists[1]);
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} else if let Some(arglists) = method_chain_args(expr, &["rposition", "is_some"]) {
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lint_search_is_some(cx, expr, "rposition", arglists[0], arglists[1]);
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}
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if in_macro(cx, expr.span) {
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return;
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}
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lint_or_fun_call(cx, expr, &name.node.as_str(), &args);
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match expr.node {
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ExprMethodCall(name, _, ref args) => {
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// Chain calls
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if let Some(arglists) = method_chain_args(expr, &["unwrap"]) {
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lint_unwrap(cx, expr, arglists[0]);
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} else if let Some(arglists) = method_chain_args(expr, &["to_string"]) {
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lint_to_string(cx, expr, arglists[0]);
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} else if let Some(arglists) = method_chain_args(expr, &["ok", "expect"]) {
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lint_ok_expect(cx, expr, arglists[0]);
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} else if let Some(arglists) = method_chain_args(expr, &["map", "unwrap_or"]) {
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lint_map_unwrap_or(cx, expr, arglists[0], arglists[1]);
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} else if let Some(arglists) = method_chain_args(expr, &["map", "unwrap_or_else"]) {
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lint_map_unwrap_or_else(cx, expr, arglists[0], arglists[1]);
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} else if let Some(arglists) = method_chain_args(expr, &["filter", "next"]) {
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lint_filter_next(cx, expr, arglists[0]);
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} else if let Some(arglists) = method_chain_args(expr, &["find", "is_some"]) {
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lint_search_is_some(cx, expr, "find", arglists[0], arglists[1]);
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} else if let Some(arglists) = method_chain_args(expr, &["position", "is_some"]) {
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lint_search_is_some(cx, expr, "position", arglists[0], arglists[1]);
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} else if let Some(arglists) = method_chain_args(expr, &["rposition", "is_some"]) {
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lint_search_is_some(cx, expr, "rposition", arglists[0], arglists[1]);
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}
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lint_or_fun_call(cx, expr, &name.node.as_str(), &args);
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}
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ExprBinary(op, ref lhs, ref rhs) if op.node == BiEq || op.node == BiNe => {
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if !lint_chars_next(cx, expr, lhs, rhs, op.node == BiEq) {
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lint_chars_next(cx, expr, rhs, lhs, op.node == BiEq);
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}
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}
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_ => (),
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}
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}
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fn check_item(&mut self, cx: &LateContext, item: &Item) {
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if in_external_macro(cx, item.span) {
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return;
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}
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if let ItemImpl(_, _, _, None, ref ty, ref items) = item.node {
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for implitem in items {
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let name = implitem.name;
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@ -570,6 +601,41 @@ fn lint_search_is_some(cx: &LateContext, expr: &Expr, search_method: &str, searc
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}
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}
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/// Checks for the `CHARS_NEXT_CMP` lint.
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fn lint_chars_next(cx: &LateContext, expr: &Expr, chain: &Expr, other: &Expr, eq: bool) -> bool {
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if_let_chain! {[
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let Some(args) = method_chain_args(chain, &["chars", "next"]),
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let ExprCall(ref fun, ref arg_char) = other.node,
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arg_char.len() == 1,
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let ExprPath(None, ref path) = fun.node,
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path.segments.len() == 1 && path.segments[0].identifier.name.as_str() == "Some"
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], {
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let self_ty = walk_ptrs_ty(cx.tcx.expr_ty_adjusted(&args[0][0]));
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if self_ty.sty != ty::TyStr {
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return false;
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}
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span_lint_and_then(cx,
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CHARS_NEXT_CMP,
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expr.span,
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"you should use the `starts_with` method",
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|db| {
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let sugg = format!("{}{}.starts_with({})",
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if eq { "" } else { "!" },
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snippet(cx, args[0][0].span, "_"),
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snippet(cx, arg_char[0].span, "_")
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);
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db.span_suggestion(expr.span, "like this", sugg);
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});
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return true;
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}}
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false
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}
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// Given a `Result<T, E>` type, return its error type (`E`)
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fn get_error_type<'a>(cx: &LateContext, ty: ty::Ty<'a>) -> Option<ty::Ty<'a>> {
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if !match_type(cx, ty, &RESULT_PATH) {
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@ -389,13 +389,14 @@ impl LateLintPass for UsedUnderscoreBinding {
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.last()
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.expect("path should always have at least one segment")
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.identifier;
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ident.name.as_str().chars().next() == Some('_') && // starts with '_'
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ident.name.as_str().chars().skip(1).next() != Some('_') && // doesn't start with "__"
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ident.name != ident.unhygienic_name && is_used(cx, expr) // not in bang macro
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ident.name.as_str().starts_with('_') &&
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!ident.name.as_str().starts_with("__") &&
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ident.name != ident.unhygienic_name &&
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is_used(cx, expr) // not in bang macro
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}
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ExprField(_, spanned) => {
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let name = spanned.node.as_str();
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name.chars().next() == Some('_') && name.chars().skip(1).next() != Some('_')
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name.starts_with('_') && !name.starts_with("__")
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}
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_ => false,
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};
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@ -292,3 +292,15 @@ struct MyError(()); // doesn't implement Debug
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struct MyErrorWithParam<T> {
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x: T
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}
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fn starts_with() {
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"".chars().next() == Some(' ');
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//~^ ERROR starts_with
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//~| HELP like this
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//~| SUGGESTION "".starts_with(' ')
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Some(' ') != "".chars().next();
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//~^ ERROR starts_with
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//~| HELP like this
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//~| SUGGESTION !"".starts_with(' ')
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}
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