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Merge pull request #549 from mcarton/ifs

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Remove and lint about useless braces in `else { if .. }`
This commit is contained in:
Manish Goregaokar 2016-01-29 03:39:27 +05:30
commit 4c14d98c9f
7 changed files with 106 additions and 67 deletions
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2
README.md
View File

@ -24,7 +24,7 @@ name
[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
[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)
[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()`
[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() }`
[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() }` and an `else { if .. } expression can be collapsed to `else if`
[cyclomatic_complexity](https://github.com/Manishearth/rust-clippy/wiki#cyclomatic_complexity) | warn | finds functions that should be split up into multiple functions
[deprecated_semver](https://github.com/Manishearth/rust-clippy/wiki#deprecated_semver) | warn | `Warn` on `#[deprecated(since = "x")]` where x is not semver
[derive_hash_not_eq](https://github.com/Manishearth/rust-clippy/wiki#derive_hash_not_eq) | warn | deriving `Hash` but implementing `PartialEq` explicitly

19
src/bit_mask.rs
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@ -148,11 +148,10 @@ fn check_bit_mask(cx: &LateContext, bit_op: BinOp_, cmp_op: BinOp_, mask_value:
mask_value,
cmp_value));
}
} else {
if mask_value == 0 {
span_lint(cx, BAD_BIT_MASK, *span, "&-masking with zero");
}
} else if mask_value == 0 {
span_lint(cx, BAD_BIT_MASK, *span, "&-masking with zero");
}
}
BiBitOr => {
if mask_value | cmp_value != cmp_value {
@ -177,10 +176,8 @@ fn check_bit_mask(cx: &LateContext, bit_op: BinOp_, cmp_op: BinOp_, mask_value:
&format!("incompatible bit mask: `_ & {}` will always be lower than `{}`",
mask_value,
cmp_value));
} else {
if mask_value == 0 {
span_lint(cx, BAD_BIT_MASK, *span, "&-masking with zero");
}
} else if mask_value == 0 {
span_lint(cx, BAD_BIT_MASK, *span, "&-masking with zero");
}
}
BiBitOr => {
@ -209,10 +206,8 @@ fn check_bit_mask(cx: &LateContext, bit_op: BinOp_, cmp_op: BinOp_, mask_value:
&format!("incompatible bit mask: `_ & {}` will never be higher than `{}`",
mask_value,
cmp_value));
} else {
if mask_value == 0 {
span_lint(cx, BAD_BIT_MASK, *span, "&-masking with zero");
}
} else if mask_value == 0 {
span_lint(cx, BAD_BIT_MASK, *span, "&-masking with zero");
}
}
BiBitOr => {

71
src/collapsible_if.rs
View File

@ -16,9 +16,11 @@ use rustc::lint::*;
use rustc_front::hir::*;
use syntax::codemap::Spanned;
use utils::{in_macro, span_help_and_lint, snippet, snippet_block};
use utils::{in_macro, snippet, snippet_block, span_lint_and_then};
/// **What it does:** This lint checks for nested `if`-statements which can be collapsed by `&&`-combining their conditions. It is `Warn` by default.
/// **What it does:** This lint checks for nested `if`-statements which can be collapsed by
/// `&&`-combining their conditions and for `else { if .. } expressions that can be collapsed to
/// `else if ..`. It is `Warn` by default.
///
/// **Why is this bad?** Each `if`-statement adds one level of nesting, which makes code look more complex than it really is.
///
@ -29,7 +31,8 @@ declare_lint! {
pub 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() }`"
can be written as `if x && y { foo() }` and an `else { if .. } expression can be collapsed to \
`else if`"
}
#[derive(Copy,Clone)]
@ -50,20 +53,44 @@ impl LateLintPass for CollapsibleIf {
}
fn check_if(cx: &LateContext, e: &Expr) {
if let ExprIf(ref check, ref then, None) = e.node {
if let Some(&Expr{ node: ExprIf(ref check_inner, ref content, None), span: sp, ..}) =
single_stmt_of_block(then) {
if e.span.expn_id != sp.expn_id {
return;
if let ExprIf(ref check, ref then, ref else_) = e.node {
match *else_ {
Some(ref else_) => {
if_let_chain! {[
let ExprBlock(ref block) = else_.node,
block.stmts.is_empty(),
block.rules == BlockCheckMode::DefaultBlock,
let Some(ref else_) = block.expr,
let ExprIf(_, _, _) = else_.node
], {
span_lint_and_then(cx,
COLLAPSIBLE_IF,
block.span,
"this `else { if .. }` block can be collapsed", |db| {
db.span_suggestion(block.span, "try",
format!("else {}",
snippet_block(cx, else_.span, "..")));
});
}}
}
None => {
if let Some(&Expr{ node: ExprIf(ref check_inner, ref content, None), span: sp, ..}) =
single_stmt_of_block(then) {
if e.span.expn_id != sp.expn_id {
return;
}
span_lint_and_then(cx,
COLLAPSIBLE_IF,
e.span,
"this if statement can be collapsed", |db| {
db.span_suggestion(e.span, "try",
format!("if {} && {} {}",
check_to_string(cx, check),
check_to_string(cx, check_inner),
snippet_block(cx, content.span, "..")));
});
}
}
span_help_and_lint(cx,
COLLAPSIBLE_IF,
e.span,
"this if statement can be collapsed",
&format!("try\nif {} && {} {}",
check_to_string(cx, check),
check_to_string(cx, check_inner),
snippet_block(cx, content.span, "..")));
}
}
}
@ -90,16 +117,14 @@ fn single_stmt_of_block(block: &Block) -> Option<&Expr> {
} else {
None
}
} else {
if block.stmts.is_empty() {
if let Some(ref p) = block.expr {
Some(p)
} else {
None
}
} else if block.stmts.is_empty() {
if let Some(ref p) = block.expr {
Some(p)
} else {
None
}
} else {
None
}
}

8
src/consts.rs
View File

@ -536,12 +536,10 @@ impl<'c, 'cc> ConstEvalLateContext<'c, 'cc> {
Plus
})
.and_then(|ty| l64.checked_add(r64).map(|v| ConstantInt(v, ty)))
} else if ln {
add_neg_int(r64, rty, l64, lty)
} else {
if ln {
add_neg_int(r64, rty, l64, lty)
} else {
add_neg_int(l64, lty, r64, rty)
}
add_neg_int(l64, lty, r64, rty)
}
}
// TODO: float (would need bignum library?)

8
src/minmax.rs
View File

@ -59,12 +59,10 @@ fn min_max<'a>(cx: &LateContext, expr: &'a Expr) -> Option<(MinMax, Constant, &'
if match_def_path(cx, def_id, &["core", "cmp", "min"]) {
fetch_const(args, Min)
} else if match_def_path(cx, def_id, &["core", "cmp", "max"]) {
fetch_const(args, Max)
} else {
if match_def_path(cx, def_id, &["core", "cmp", "max"]) {
fetch_const(args, Max)
} else {
None
}
None
}
} else {
None

41
src/shadow.rs
View File

@ -204,29 +204,28 @@ fn lint_shadow<T>(cx: &LateContext, name: Name, span: Span, lspan: Span, init: &
snippet(cx, lspan, "_"),
snippet(cx, expr.span, "..")));
note_orig(cx, db, SHADOW_SAME, prev_span);
} else if contains_self(name, expr) {
let db = span_note_and_lint(cx,
SHADOW_REUSE,
lspan,
&format!("{} is shadowed by {} which reuses the original value",
snippet(cx, lspan, "_"),
snippet(cx, expr.span, "..")),
expr.span,
"initialization happens here");
note_orig(cx, db, SHADOW_REUSE, prev_span);
} else {
if contains_self(name, expr) {
let db = span_note_and_lint(cx,
SHADOW_REUSE,
lspan,
&format!("{} is shadowed by {} which reuses the original value",
snippet(cx, lspan, "_"),
snippet(cx, expr.span, "..")),
expr.span,
"initialization happens here");
note_orig(cx, db, SHADOW_REUSE, prev_span);
} else {
let db = span_note_and_lint(cx,
SHADOW_UNRELATED,
lspan,
&format!("{} is shadowed by {}",
snippet(cx, lspan, "_"),
snippet(cx, expr.span, "..")),
expr.span,
"initialization happens here");
note_orig(cx, db, SHADOW_UNRELATED, prev_span);
}
let db = span_note_and_lint(cx,
SHADOW_UNRELATED,
lspan,
&format!("{} is shadowed by {}",
snippet(cx, lspan, "_"),
snippet(cx, expr.span, "..")),
expr.span,
"initialization happens here");
note_orig(cx, db, SHADOW_UNRELATED, prev_span);
}
} else {
let db = span_lint(cx,
SHADOW_UNRELATED,

24
tests/compile-fail/collapsible_if.rs
View File

@ -17,6 +17,30 @@ fn main() {
}
}
// Collaspe `else { if .. }` to `else if ..`
if x == "hello" {
print!("Hello ");
} else { //~ERROR: this `else { if .. }`
//~| HELP try
//~| SUGGESTION else if y == "world"
if y == "world" {
println!("world!")
}
}
if x == "hello" {
print!("Hello ");
} else { //~ERROR this `else { if .. }`
//~| HELP try
//~| SUGGESTION else if y == "world"
if y == "world" {
println!("world")
}
else {
println!("!")
}
}
// Works because any if with an else statement cannot be collapsed.
if x == "hello" {
if y == "world" {