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spelling fix, rework needless_bool with snippet (fixes #150)

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This commit is contained in:
Georg Brandl 2015-08-13 09:44:03 +02:00
parent 1d64553bc6
commit 8a98736f51
3 changed files with 30 additions and 20 deletions
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40
src/needless_bool.rs
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@ -10,7 +10,7 @@ use syntax::ast::*;
use syntax::ast_util::{is_comparison_binop, binop_to_string};
use syntax::ptr::P;
use syntax::codemap::Span;
use utils::{de_p, span_lint};
use utils::{de_p, span_lint, snippet};
declare_lint! {
pub NEEDLESS_BOOL,
@ -28,20 +28,30 @@ impl LintPass for NeedlessBool {
}
fn check_expr(&mut self, cx: &Context, e: &Expr) {
if let ExprIf(_, ref then_block, Option::Some(ref else_expr)) = e.node {
if let ExprIf(ref pred, ref then_block, Some(ref else_expr)) = e.node {
match (fetch_bool_block(then_block), fetch_bool_expr(else_expr)) {
(Option::Some(true), Option::Some(true)) => {
(Some(true), Some(true)) => {
span_lint(cx, NEEDLESS_BOOL, e.span,
"your if-then-else expression will always return true"); },
(Option::Some(true), Option::Some(false)) => {
"this if-then-else expression will always return true"); },
(Some(false), Some(false)) => {
span_lint(cx, NEEDLESS_BOOL, e.span,
"you can reduce your if statement to its predicate"); },
(Option::Some(false), Option::Some(true)) => {
span_lint(cx, NEEDLESS_BOOL, e.span,
"you can reduce your if statement to `!` + its predicate"); },
(Option::Some(false), Option::Some(false)) => {
span_lint(cx, NEEDLESS_BOOL, e.span,
"your if-then-else expression will always return false"); },
"this if-then-else expression will always return false"); },
(Some(true), Some(false)) => {
let pred_snip = snippet(cx, pred.span, "..");
let hint = if pred_snip == ".." { "its predicate".into() } else {
format!("`{}`", pred_snip)
};
span_lint(cx, NEEDLESS_BOOL, e.span, &format!(
"you can reduce this if-then-else expression to just {}", hint));
},
(Some(false), Some(true)) => {
let pred_snip = snippet(cx, pred.span, "..");
let hint = if pred_snip == ".." { "`!` and its predicate".into() } else {
format!("`!{}`", pred_snip)
};
span_lint(cx, NEEDLESS_BOOL, e.span, &format!(
"you can reduce this if-then-else expression to just {}", hint));
},
_ => ()
}
}
@ -51,14 +61,14 @@ impl LintPass for NeedlessBool {
fn fetch_bool_block(block: &Block) -> Option<bool> {
if block.stmts.is_empty() {
block.expr.as_ref().map(de_p).and_then(fetch_bool_expr)
} else { Option::None }
} else { None }
}
fn fetch_bool_expr(expr: &Expr) -> Option<bool> {
match &expr.node {
&ExprBlock(ref block) => fetch_bool_block(block),
&ExprLit(ref lit_ptr) => if let &LitBool(value) = &lit_ptr.node {
Option::Some(value) } else { Option::None },
_ => Option::None
Some(value) } else { None },
_ => None
}
}

2
tests/compile-fail/eq_op.rs
View File

@ -16,7 +16,7 @@ fn main() {
1.5 < 1.5; //~ERROR equal expressions
1u64 >= 1u64; //~ERROR equal expressions
// casts, methods, parenthesis
// casts, methods, parentheses
(1 as u64) & (1 as u64); //~ERROR equal expressions
1 ^ ((((((1)))))); //~ERROR equal expressions
id((1)) | id(1); //~ERROR equal expressions

8
tests/compile-fail/needless_bool.rs
View File

@ -4,9 +4,9 @@
#[deny(needless_bool)]
fn main() {
let x = true;
if x { true } else { true }; //~ERROR your if-then-else expression will always return true
if x { false } else { false }; //~ERROR your if-then-else expression will always return false
if x { true } else { false }; //~ERROR you can reduce your if statement to its predicate
if x { false } else { true }; //~ERROR you can reduce your if statement to `!` + its predicate
if x { true } else { true }; //~ERROR this if-then-else expression will always return true
if x { false } else { false }; //~ERROR this if-then-else expression will always return false
if x { true } else { false }; //~ERROR you can reduce this if-then-else expression to just `x`
if x { false } else { true }; //~ERROR you can reduce this if-then-else expression to just `!x`
if x { x } else { false }; // would also be questionable, but we don't catch this yet
}