Merge pull request #2849 from mikerite/issue_2741

Fix #2741

Author: oli-obk

clippy_lints/src/consts.rs

@@ -122,21 +122,32 @@ impl Hash for Constant {
     }
 }
 
-impl PartialOrd for Constant {
-    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
-        match (self, other) {
+impl Constant {
+    pub fn partial_cmp(tcx: TyCtxt, cmp_type: &ty::TypeVariants, left: &Self, right: &Self) -> Option<Ordering> {
+        match (left, right) {
             (&Constant::Str(ref ls), &Constant::Str(ref rs)) => Some(ls.cmp(rs)),
             (&Constant::Char(ref l), &Constant::Char(ref r)) => Some(l.cmp(r)),
-            (&Constant::Int(l), &Constant::Int(r)) => Some(l.cmp(&r)),
+            (&Constant::Int(l), &Constant::Int(r)) => {
+                if let ty::TyInt(int_ty) = *cmp_type {
+                    Some(sext(tcx, l, int_ty).cmp(&sext(tcx, r, int_ty)))
+                } else {
+                    Some(l.cmp(&r))
+                }
+            },
             (&Constant::F64(l), &Constant::F64(r)) => l.partial_cmp(&r),
             (&Constant::F32(l), &Constant::F32(r)) => l.partial_cmp(&r),
             (&Constant::Bool(ref l), &Constant::Bool(ref r)) => Some(l.cmp(r)),
-            (&Constant::Tuple(ref l), &Constant::Tuple(ref r)) | (&Constant::Vec(ref l), &Constant::Vec(ref r)) => {
-                l.partial_cmp(r)
-            },
-            (&Constant::Repeat(ref lv, ref ls), &Constant::Repeat(ref rv, ref rs)) => match lv.partial_cmp(rv) {
-                Some(Equal) => Some(ls.cmp(rs)),
-                x => x,
+            (&Constant::Tuple(ref l), &Constant::Tuple(ref r)) | (&Constant::Vec(ref l), &Constant::Vec(ref r)) => l
+                .iter()
+                .zip(r.iter())
+                .map(|(li, ri)| Constant::partial_cmp(tcx, cmp_type, li, ri))
+                .find(|r| r.map_or(true, |o| o != Ordering::Equal))
+                .unwrap_or_else(|| Some(l.len().cmp(&r.len()))),
+            (&Constant::Repeat(ref lv, ref ls), &Constant::Repeat(ref rv, ref rs)) => {
+                match Constant::partial_cmp(tcx, cmp_type, lv, rv) {
+                    Some(Equal) => Some(ls.cmp(rs)),
+                    x => x,
+                }
             },
             _ => None, // TODO: Are there any useful inter-type orderings?
         }

clippy_lints/src/minmax.rs

@@ -1,8 +1,8 @@
 use crate::consts::{constant_simple, Constant};
-use rustc::lint::*;
-use rustc::hir::*;
-use std::cmp::{Ordering, PartialOrd};
 use crate::utils::{match_def_path, opt_def_id, paths, span_lint};
+use rustc::hir::*;
+use rustc::lint::*;
+use std::cmp::Ordering;
 
 /// **What it does:** Checks for expressions where `std::cmp::min` and `max` are
 /// used to clamp values, but switched so that the result is constant.
@@ -36,14 +36,22 @@ impl LintPass for MinMaxPass {
 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for MinMaxPass {
     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
         if let Some((outer_max, outer_c, oe)) = min_max(cx, expr) {
-            if let Some((inner_max, inner_c, _)) = min_max(cx, oe) {
+            if let Some((inner_max, inner_c, ie)) = min_max(cx, oe) {
                 if outer_max == inner_max {
                     return;
                 }
-                match (outer_max, outer_c.partial_cmp(&inner_c)) {
+                match (
+                    outer_max,
+                    Constant::partial_cmp(cx.tcx, &cx.tables.expr_ty(ie).sty, &outer_c, &inner_c),
+                ) {
                     (_, None) | (MinMax::Max, Some(Ordering::Less)) | (MinMax::Min, Some(Ordering::Greater)) => (),
                     _ => {
-                        span_lint(cx, MIN_MAX, expr.span, "this min/max combination leads to constant result");
+                        span_lint(
+                            cx,
+                            MIN_MAX,
+                            expr.span,
+                            "this min/max combination leads to constant result",
+                        );
                     },
                 }
             }

tests/ui/min_max.rs

@@ -23,6 +23,9 @@ fn main() {
 
     min(1, max(LARGE, x)); // no error, we don't lookup consts here
 
+    let y = 2isize;
+    min(max(y, -1), 3);
+
     let s;
     s = "Hello";
 

tests/ui/min_max.stderr

@@ -31,15 +31,15 @@ error: this min/max combination leads to constant result
    |     ^^^^^^^^^^^^^^^^^^^^^^^
 
 error: this min/max combination leads to constant result
-  --> $DIR/min_max.rs:29:5
+  --> $DIR/min_max.rs:32:5
    |
-29 |     min("Apple", max("Zoo", s));
+32 |     min("Apple", max("Zoo", s));
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: this min/max combination leads to constant result
-  --> $DIR/min_max.rs:30:5
+  --> $DIR/min_max.rs:33:5
    |
-30 |     max(min(s, "Apple"), "Zoo");
+33 |     max(min(s, "Apple"), "Zoo");
    |     ^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
 error: aborting due to 7 previous errors