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Use span_lint_and_then as per feedback
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Michael Recachinas committed Sep 23, 2017
1 parent bb40bd6 commit 21e9a12
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Showing 2 changed files with 106 additions and 26 deletions.
112 changes: 90 additions & 22 deletions clippy_lints/src/int_plus_one.rs
View file
Expand Up @@ -3,7 +3,7 @@
use rustc::lint::*;
use syntax::ast::*;

use utils::span_help_and_lint;
use utils::{span_lint_and_then, snippet_opt};

/// **What it does:** Checks for usage of `x >= y + 1` or `x - 1 >= y` (and `<=`) in a block
///
Expand Down Expand Up @@ -45,6 +45,11 @@ impl LintPass for IntPlusOne {
// x + 1 <= y
// x <= y - 1

enum Side {
LHS,
RHS,
}

impl IntPlusOne {
#[allow(cast_sign_loss)]
fn check_lit(&self, lit: &Lit, target_value: i128) -> bool {
Expand All @@ -54,62 +59,125 @@ impl IntPlusOne {
false
}

fn check_binop(&self, binop: BinOpKind, lhs: &Expr, rhs: &Expr) -> bool {
fn check_binop(&self, cx: &EarlyContext, block: &Expr, binop: BinOpKind, lhs: &Expr, rhs: &Expr) -> Option<(bool, Option<String>)> {
match (binop, &lhs.node, &rhs.node) {
// case where `x - 1 >= ...` or `-1 + x >= ...`
(BinOpKind::Ge, &ExprKind::Binary(ref lhskind, ref lhslhs, ref lhsrhs), _) => {
match (lhskind.node, &lhslhs.node, &lhsrhs.node) {
// `-1 + x`
(BinOpKind::Add, &ExprKind::Lit(ref lit), _) => self.check_lit(lit, -1),
(BinOpKind::Add, &ExprKind::Lit(ref lit), _) => {
let recommendation = self.generate_recommendation(cx, binop, lhsrhs, rhs, Side::LHS);
if self.check_lit(lit, -1) {
self.emit_warning(cx, block, recommendation)
}
},
// `x - 1`
(BinOpKind::Sub, _, &ExprKind::Lit(ref lit)) => self.check_lit(lit, 1),
_ => false
(BinOpKind::Sub, _, &ExprKind::Lit(ref lit)) => {
let recommendation = self.generate_recommendation(cx, binop, lhslhs, rhs, Side::LHS);
if self.check_lit(lit, 1) {
self.emit_warning(cx, block, recommendation)
}
}
_ => ()
}
},
// case where `... >= y + 1` or `... >= 1 + y`
(BinOpKind::Ge, _, &ExprKind::Binary(ref rhskind, ref rhslhs, ref rhsrhs)) if rhskind.node == BinOpKind::Add => {
match (&rhslhs.node, &rhsrhs.node) {
// `y + 1` and `1 + y`
(&ExprKind::Lit(ref lit), _)|(_, &ExprKind::Lit(ref lit)) => self.check_lit(lit, 1),
_ => false
(&ExprKind::Lit(ref lit), _) => {
let recommendation = self.generate_recommendation(cx, binop, rhsrhs, lhs, Side::RHS);
if self.check_lit(lit, 1) {
self.emit_warning(cx, block, recommendation)
}
},
(_, &ExprKind::Lit(ref lit)) => {
let recommendation = self.generate_recommendation(cx, binop, rhslhs, lhs, Side::RHS);
if self.check_lit(lit, 1) {
self.emit_warning(cx, block, recommendation)
}
},
_ => ()
}
},
// case where `x + 1 <= ...` or `1 + x <= ...`
(BinOpKind::Le, &ExprKind::Binary(ref lhskind, ref lhslhs, ref lhsrhs), _) if lhskind.node == BinOpKind::Add => {
match (&lhslhs.node, &lhsrhs.node) {
// `1 + x` and `x + 1`
(&ExprKind::Lit(ref lit), _)|(_, &ExprKind::Lit(ref lit)) => self.check_lit(lit, 1),
_ => false
(&ExprKind::Lit(ref lit), _) => {
let recommendation = self.generate_recommendation(cx, binop, lhsrhs, rhs, Side::LHS);
if self.check_lit(lit, 1) {
self.emit_warning(cx, block, recommendation)
}
},
(_, &ExprKind::Lit(ref lit)) => {
let recommendation = self.generate_recommendation(cx, binop, lhslhs, rhs, Side::LHS);
if self.check_lit(lit, 1) {
self.emit_warning(cx, block, recommendation)
}
},
_ => ()
}
},
// case where `... >= y - 1` or `... >= -1 + y`
(BinOpKind::Le, _, &ExprKind::Binary(ref rhskind, ref rhslhs, ref rhsrhs)) => {
match (rhskind.node, &rhslhs.node, &rhsrhs.node) {
// `-1 + y`
(BinOpKind::Add, &ExprKind::Lit(ref lit), _) => self.check_lit(lit, -1),
(BinOpKind::Add, &ExprKind::Lit(ref lit), _) => {
let recommendation = self.generate_recommendation(cx, binop, rhsrhs, lhs, Side::RHS);
if self.check_lit(lit, -1) {
self.emit_warning(cx, block, recommendation)
}
},
// `y - 1`
(BinOpKind::Sub, _, &ExprKind::Lit(ref lit)) => self.check_lit(lit, 1),
_ => false
(BinOpKind::Sub, _, &ExprKind::Lit(ref lit)) => {
let recommendation = self.generate_recommendation(cx, binop, rhslhs, lhs, Side::RHS);
if self.check_lit(lit, 1) {
self.emit_warning(cx, block, recommendation)
}
},
_ => ()
}
},
_ => false
_ => ()
}
}

fn generate_recommendation(&self, cx: &EarlyContext, binop: BinOpKind, node: &Expr, other_side: &Expr, side: Side) -> Option<String> {
let binop_string = match binop {
BinOpKind::Ge => ">",
BinOpKind::Le => "<",
_ => return None
};
if let Some(snippet) = snippet_opt(cx, node.span) {
if let Some(other_side_snippet) = snippet_opt(cx, other_side.span) {
let rec = match side {
Side::LHS => Some(format!("{} {} {}", snippet, binop_string, other_side_snippet)),
Side::RHS => Some(format!("{} {} {}", other_side_snippet, binop_string, snippet)),
};
return rec;
}
}
None
}

fn emit_warning(&self, cx: &EarlyContext, block: &Expr, recommendation: Option<String>) {
if let Some(rec) = recommendation {
span_lint_and_then(cx,
INT_PLUS_ONE,
block.span,
"Unnecessary `>= y + 1` or `x - 1 >=`",
|db| {
db.span_suggestion(block.span, "change `>= y + 1` to `> y` as shown", rec);
});
}
}
}

impl EarlyLintPass for IntPlusOne {
fn check_expr(&mut self, cx: &EarlyContext, item: &Expr) {
if let ExprKind::Binary(ref kind, ref lhs, ref rhs) = item.node {
if self.check_binop(kind.node, lhs, rhs) {
span_help_and_lint(
cx,
INT_PLUS_ONE,
item.span,
"Unnecessary `>= y + 1` or `x - 1 >=`",
"Consider reducing `x >= y + 1` or `x - 1 >= y` to `x > y`",
);
}
self.check_binop(cx, item, kind.node, lhs, rhs);
}
}
}
20 changes: 16 additions & 4 deletions tests/ui/int_plus_one.stderr
View file
Expand Up @@ -5,31 +5,43 @@ error: Unnecessary `>= y + 1` or `x - 1 >=`
| ^^^^^^^^^^
|
= note: `-D int-plus-one` implied by `-D warnings`
= help: Consider reducing `x >= y + 1` or `x - 1 >= y` to `x > y`
help: change `>= y + 1` to `> y` as shown
|
10 | x > y;
| ^^^^^

error: Unnecessary `>= y + 1` or `x - 1 >=`
--> $DIR/int_plus_one.rs:11:5
|
11 | y + 1 <= x;
| ^^^^^^^^^^
|
= help: Consider reducing `x >= y + 1` or `x - 1 >= y` to `x > y`
help: change `>= y + 1` to `> y` as shown
|
11 | y < x;
| ^^^^^

error: Unnecessary `>= y + 1` or `x - 1 >=`
--> $DIR/int_plus_one.rs:13:5
|
13 | x - 1 >= y;
| ^^^^^^^^^^
|
= help: Consider reducing `x >= y + 1` or `x - 1 >= y` to `x > y`
help: change `>= y + 1` to `> y` as shown
|
13 | x > y;
| ^^^^^

error: Unnecessary `>= y + 1` or `x - 1 >=`
--> $DIR/int_plus_one.rs:14:5
|
14 | y <= x - 1;
| ^^^^^^^^^^
|
= help: Consider reducing `x >= y + 1` or `x - 1 >= y` to `x > y`
help: change `>= y + 1` to `> y` as shown
|
14 | y < x;
| ^^^^^

error: aborting due to 4 previous errors

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