From 405d7c691e2ad6b21e044b39c736b1e1a7db99cf Mon Sep 17 00:00:00 2001 From: Devon Hollowood Date: Fri, 29 Jan 2016 15:15:57 -0800 Subject: [PATCH] Add for_loop_over_result lint --- README.md | 5 ++-- src/lib.rs | 1 + src/loops.rs | 35 ++++++++++++++++++++----- tests/compile-fail/for_loop.rs | 48 +++++++++++++++++++++++++++++----- 4 files changed, 74 insertions(+), 15 deletions(-) diff --git a/README.md b/README.md index b58d2f67ac20..39b848d036bc 100644 --- a/README.md +++ b/README.md @@ -6,7 +6,7 @@ A collection of lints to catch common mistakes and improve your Rust code. [Jump to usage instructions](#usage) ##Lints -There are 102 lints included in this crate: +There are 103 lints included in this crate: name | default | meaning ---------------------------------------------------------------------------------------------------------------|---------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ @@ -37,7 +37,8 @@ name [extend_from_slice](https://github.com/Manishearth/rust-clippy/wiki#extend_from_slice) | warn | `.extend_from_slice(_)` is a faster way to extend a Vec by a slice [filter_next](https://github.com/Manishearth/rust-clippy/wiki#filter_next) | warn | using `filter(p).next()`, which is more succinctly expressed as `.find(p)` [float_cmp](https://github.com/Manishearth/rust-clippy/wiki#float_cmp) | warn | using `==` or `!=` on float values (as floating-point operations usually involve rounding errors, it is always better to check for approximate equality within small bounds) -[for_loop_over_option](https://github.com/Manishearth/rust-clippy/wiki#for_loop_over_option) | warn | for-looping over an Option, which is more clear as an `if let` +[for_loop_over_option](https://github.com/Manishearth/rust-clippy/wiki#for_loop_over_option) | warn | for-looping over an `Option`, which is more clearly expressed as an `if let` +[for_loop_over_result](https://github.com/Manishearth/rust-clippy/wiki#for_loop_over_result) | warn | for-looping over a `Result`, which is more clearly expressed as an `if let` [identity_op](https://github.com/Manishearth/rust-clippy/wiki#identity_op) | warn | using identity operations, e.g. `x + 0` or `y / 1` [ineffective_bit_mask](https://github.com/Manishearth/rust-clippy/wiki#ineffective_bit_mask) | warn | expressions where a bit mask will be rendered useless by a comparison, e.g. `(x | 1) > 2` [inline_always](https://github.com/Manishearth/rust-clippy/wiki#inline_always) | warn | `#[inline(always)]` is a bad idea in most cases diff --git a/src/lib.rs b/src/lib.rs index b955a3370762..a6f5aa974850 100644 --- a/src/lib.rs +++ b/src/lib.rs @@ -193,6 +193,7 @@ pub fn plugin_registrar(reg: &mut Registry) { loops::EXPLICIT_COUNTER_LOOP, loops::EXPLICIT_ITER_LOOP, loops::FOR_LOOP_OVER_OPTION, + loops::FOR_LOOP_OVER_RESULT, loops::ITER_NEXT_LOOP, loops::NEEDLESS_RANGE_LOOP, loops::REVERSE_RANGE_LOOP, diff --git a/src/loops.rs b/src/loops.rs index dd7f7cbe3eb4..74ff9edcb6b7 100644 --- a/src/loops.rs +++ b/src/loops.rs @@ -11,7 +11,7 @@ use std::collections::{HashSet, HashMap}; use utils::{snippet, span_lint, get_parent_expr, match_trait_method, match_type, in_external_macro, expr_block, span_help_and_lint, is_integer_literal, get_enclosing_block}; -use utils::{HASHMAP_PATH, VEC_PATH, LL_PATH, OPTION_PATH}; +use utils::{HASHMAP_PATH, VEC_PATH, LL_PATH, OPTION_PATH, RESULT_PATH}; /// **What it does:** This lint checks for looping over the range of `0..len` of some collection just to get the values by index. It is `Warn` by default. /// @@ -48,7 +48,7 @@ declare_lint!{ pub EXPLICIT_ITER_LOOP, Warn, declare_lint!{ pub ITER_NEXT_LOOP, Warn, "for-looping over `_.next()` which is probably not intended" } -/// **What it does:** This lint checks for `for` loops over Option values. It is `Warn` by default. +/// **What it does:** This lint checks for `for` loops over `Option` values. It is `Warn` by default. /// /// **Why is this bad?** Readability. This is more clearly expressed as an `if let`. /// @@ -56,7 +56,17 @@ declare_lint!{ pub ITER_NEXT_LOOP, Warn, /// /// **Example:** `for x in option { .. }`. This should be `if let Some(x) = option { .. }`. declare_lint!{ pub FOR_LOOP_OVER_OPTION, Warn, - "for-looping over an Option, which is more clear as an `if let`" } + "for-looping over an `Option`, which is more clearly expressed as an `if let`" } + +/// **What it does:** This lint checks for `for` loops over `Result` values. It is `Warn` by default. +/// +/// **Why is this bad?** Readability. This is more clearly expressed as an `if let`. +/// +/// **Known problems:** None +/// +/// **Example:** `for x in result { .. }`. This should be `if let Ok(x) = result { .. }`. +declare_lint!{ pub FOR_LOOP_OVER_RESULT, Warn, + "for-looping over a `Result`, which is more clearly expressed as an `if let`" } /// **What it does:** This lint detects `loop + match` combinations that are easier written as a `while let` loop. It is `Warn` by default. /// @@ -417,24 +427,35 @@ fn check_for_loop_arg(cx: &LateContext, pat: &Pat, arg: &Expr, expr: &Expr) { } } if !next_loop_linted { - check_option_looping(cx, pat, arg); + check_arg_type(cx, pat, arg); } } -/// Check for `for` loops over `Option`s -fn check_option_looping(cx: &LateContext, pat: &Pat, arg: &Expr) { +/// Check for `for` loops over `Option`s and `Results` +fn check_arg_type(cx: &LateContext, pat: &Pat, arg: &Expr) { let ty = cx.tcx.expr_ty(arg); if match_type(cx, ty, &OPTION_PATH) { span_help_and_lint( cx, FOR_LOOP_OVER_OPTION, arg.span, - &format!("for loop over `{0}`, which is an Option. This is more readably written as \ + &format!("for loop over `{0}`, which is an `Option`. This is more readably written as \ an `if let` statement.", snippet(cx, arg.span, "_")), &format!("consider replacing `for {0} in {1}` with `if let Some({0}) = {1}`", snippet(cx, pat.span, "_"), snippet(cx, arg.span, "_")) ); } + else if match_type(cx, ty, &RESULT_PATH) { + span_help_and_lint( + cx, + FOR_LOOP_OVER_RESULT, + arg.span, + &format!("for loop over `{0}`, which is a `Result`. This is more readably written as \ + an `if let` statement.", snippet(cx, arg.span, "_")), + &format!("consider replacing `for {0} in {1}` with `if let Ok({0}) = {1}`", + snippet(cx, pat.span, "_"), snippet(cx, arg.span, "_")) + ); + } } fn check_for_loop_explicit_counter(cx: &LateContext, arg: &Expr, body: &Expr, expr: &Expr) { diff --git a/tests/compile-fail/for_loop.rs b/tests/compile-fail/for_loop.rs index a45dc4bbb355..1fcbbf54d1f2 100644 --- a/tests/compile-fail/for_loop.rs +++ b/tests/compile-fail/for_loop.rs @@ -4,21 +4,51 @@ use std::collections::*; #[deny(clippy)] -fn for_loop_over_option() { +fn for_loop_over_option_and_result() { let option = Some(1); + let result = option.ok_or("x not found"); let v = vec![0,1,2]; // check FOR_LOOP_OVER_OPTION lint + for x in option { - //~^ ERROR for loop over `option`, which is an Option. + //~^ ERROR for loop over `option`, which is an `Option`. //~| HELP consider replacing `for x in option` with `if let Some(x) = option` println!("{}", x); } - // make sure LOOP_OVER_NEXT lint takes precedence + // check FOR_LOOP_OVER_RESULT lint + + for x in result { + //~^ ERROR for loop over `result`, which is a `Result`. + //~| HELP consider replacing `for x in result` with `if let Ok(x) = result` + println!("{}", x); + } + + for x in option.ok_or("x not found") { + //~^ ERROR for loop over `option.ok_or("x not found")`, which is a `Result`. + //~| HELP consider replacing `for x in option.ok_or("x not found")` with `if let Ok(x) = option.ok_or("x not found")` + println!("{}", x); + } + + // make sure LOOP_OVER_NEXT lint takes precedence when next() is the last call in the chain + for x in v.iter().next() { //~^ ERROR you are iterating over `Iterator::next()` which is an Option - // TODO: make sure we don't lint twice + println!("{}", x); + } + + // make sure we lint when next() is not the last call in the chain + + for x in v.iter().next().and(Some(0)) { + //~^ ERROR for loop over `v.iter().next().and(Some(0))`, which is an `Option` + //~| HELP consider replacing `for x in v.iter().next().and(Some(0))` with `if let Some(x) = v.iter().next().and(Some(0))` + println!("{}", x); + } + + for x in v.iter().next().ok_or("x not found") { + //~^ ERROR for loop over `v.iter().next().ok_or("x not found")`, which is a `Result` + //~| HELP consider replacing `for x in v.iter().next().ok_or("x not found")` with `if let Ok(x) = v.iter().next().ok_or("x not found")` println!("{}", x); } @@ -29,11 +59,17 @@ fn for_loop_over_option() { println!("{}", x); } - // while let false positive + // while let false positive for Option while let Some(x) = option { println!("{}", x); break; } + + // while let false positive for Option + while let Ok(x) = result { + println!("{}", x); + break; + } } struct Unrelated(Vec); @@ -243,5 +279,5 @@ fn main() { for _v in &vec { index += 1 } println!("index: {}", index); - for_loop_over_option(); + for_loop_over_option_and_result(); }