[comparison_chain] #4827 Check core::cmp::Ord
is implemented
Only emit lint, if `cmp` is actually available on the type being compared. Don't emit lint in cases where only `PartialOrd` is implemented.
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@ -1,4 +1,6 @@
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use crate::utils::{if_sequence, parent_node_is_if_expr, span_help_and_lint, SpanlessEq};
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use crate::utils::{
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get_trait_def_id, if_sequence, implements_trait, parent_node_is_if_expr, paths, span_help_and_lint, SpanlessEq,
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};
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use rustc::hir::*;
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use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
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use rustc::{declare_lint_pass, declare_tool_lint};
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@ -84,6 +86,14 @@ impl<'a, 'tcx> LateLintPass<'a, 'tcx> for ComparisonChain {
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{
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return;
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}
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// Check that the type being compared implements `core::cmp::Ord`
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let ty = cx.tables.expr_ty(lhs1);
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let is_ord = get_trait_def_id(cx, &paths::ORD).map_or(false, |id| implements_trait(cx, ty, id, &[]));
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if !is_ord {
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return;
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}
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} else {
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// We only care about comparison chains
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return;
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@ -76,4 +76,65 @@ fn f(x: u8, y: u8, z: u8) {
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}
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}
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#[allow(clippy::float_cmp)]
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fn g(x: f64, y: f64, z: f64) {
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// Ignored: f64 doesn't implement Ord
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if x > y {
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a()
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} else if x < y {
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b()
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}
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// Ignored: f64 doesn't implement Ord
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if x > y {
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a()
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} else if x < y {
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b()
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} else {
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c()
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}
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// Ignored: f64 doesn't implement Ord
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if x > y {
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a()
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} else if y > x {
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b()
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} else {
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c()
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}
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// Ignored: f64 doesn't implement Ord
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if x > 1.0 {
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a()
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} else if x < 1.0 {
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b()
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} else if x == 1.0 {
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c()
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}
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}
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fn h<T: Ord>(x: T, y: T, z: T) {
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if x > y {
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a()
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} else if x < y {
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b()
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}
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if x > y {
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a()
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} else if x < y {
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b()
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} else {
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c()
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}
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if x > y {
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a()
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} else if y > x {
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b()
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} else {
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c()
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}
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}
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fn main() {}
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@ -53,5 +53,45 @@ LL | | }
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= help: Consider rewriting the `if` chain to use `cmp` and `match`.
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error: aborting due to 4 previous errors
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error: `if` chain can be rewritten with `match`
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--> $DIR/comparison_chain.rs:117:5
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LL | / if x > y {
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LL | | a()
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LL | | } else if x < y {
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LL | | b()
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LL | | }
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| |_____^
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= help: Consider rewriting the `if` chain to use `cmp` and `match`.
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error: `if` chain can be rewritten with `match`
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--> $DIR/comparison_chain.rs:123:5
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LL | / if x > y {
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LL | | a()
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LL | | } else if x < y {
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LL | | b()
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LL | | } else {
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LL | | c()
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LL | | }
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| |_____^
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= help: Consider rewriting the `if` chain to use `cmp` and `match`.
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error: `if` chain can be rewritten with `match`
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--> $DIR/comparison_chain.rs:131:5
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LL | / if x > y {
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LL | | a()
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LL | | } else if y > x {
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LL | | b()
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LL | | } else {
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LL | | c()
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LL | | }
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| |_____^
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= help: Consider rewriting the `if` chain to use `cmp` and `match`.
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error: aborting due to 7 previous errors
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