Rollup merge of #107389 - zvavybir:master, r=estebank

Fixing confusion between mod and remainder

Like many programming languages, rust too confuses remainder and modulus.  The `%` operator and the associated `Rem` trait is (as the trait name suggests) the remainder, but since most people are linguistically more familiar with the modulus the documentation sometimes claims otherwise.  This PR tries to fix this problem in rustc.

7 files changed, 10 insertions, 8 deletions

diff --git a/compiler/rustc_hir_typeck/src/op.rs b/compiler/rustc_hir_typeck/src/op.rs
index 78cea1f4d8d..67769fe4478 100644
--- a/compiler/rustc_hir_typeck/src/op.rs
+++ b/compiler/rustc_hir_typeck/src/op.rs
@@ -335,7 +335,9 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                 format!("cannot divide `{lhs_ty}` by `{rhs_ty}`")
                             }
                             hir::BinOpKind::Rem => {
-                                format!("cannot mod `{lhs_ty}` by `{rhs_ty}`")
+                                format!(
+                                    "cannot calculate the remainder of `{lhs_ty}` divided by `{rhs_ty}`"
+                                )
                             }
                             hir::BinOpKind::BitAnd => {
                                 format!("no implementation for `{lhs_ty} & {rhs_ty}`")
diff --git a/library/core/src/ops/arith.rs b/library/core/src/ops/arith.rs
index 75c52d3ecfc..cc13db5c956 100644
--- a/library/core/src/ops/arith.rs
+++ b/library/core/src/ops/arith.rs
@@ -545,7 +545,7 @@ div_impl_float! { f32 f64 }
 #[lang = "rem"]
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_on_unimplemented(
-    message = "cannot mod `{Self}` by `{Rhs}`",
+    message = "cannot calculate the remainder of `{Self}` divided by `{Rhs}`",
     label = "no implementation for `{Self} % {Rhs}`"
 )]
 #[doc(alias = "%")]
@@ -981,7 +981,7 @@ div_assign_impl! { usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128 f32 f64 }
 #[lang = "rem_assign"]
 #[stable(feature = "op_assign_traits", since = "1.8.0")]
 #[rustc_on_unimplemented(
-    message = "cannot mod-assign `{Self}` by `{Rhs}``",
+    message = "cannot calculate and assign the remainder of `{Self}` divided by `{Rhs}`",
     label = "no implementation for `{Self} %= {Rhs}`"
 )]
 #[doc(alias = "%")]
diff --git a/tests/ui/binop/binary-op-on-double-ref.fixed b/tests/ui/binop/binary-op-on-double-ref.fixed
index de9dc19af29..586d2568c30 100644
--- a/tests/ui/binop/binary-op-on-double-ref.fixed
+++ b/tests/ui/binop/binary-op-on-double-ref.fixed
@@ -3,7 +3,7 @@ fn main() {
     let v = vec![1, 2, 3, 4, 5, 6, 7, 8, 9];
     let vr = v.iter().filter(|x| {
         *x % 2 == 0
-        //~^ ERROR cannot mod `&&{integer}` by `{integer}`
+        //~^ ERROR cannot calculate the remainder of `&&{integer}` divided by `{integer}`
     });
     println!("{:?}", vr);
 }
diff --git a/tests/ui/binop/binary-op-on-double-ref.rs b/tests/ui/binop/binary-op-on-double-ref.rs
index 2616c560cbe..48ee445466e 100644
--- a/tests/ui/binop/binary-op-on-double-ref.rs
+++ b/tests/ui/binop/binary-op-on-double-ref.rs
@@ -3,7 +3,7 @@ fn main() {
     let v = vec![1, 2, 3, 4, 5, 6, 7, 8, 9];
     let vr = v.iter().filter(|x| {
         x % 2 == 0
-        //~^ ERROR cannot mod `&&{integer}` by `{integer}`
+        //~^ ERROR cannot calculate the remainder of `&&{integer}` divided by `{integer}`
     });
     println!("{:?}", vr);
 }
diff --git a/tests/ui/binop/binary-op-on-double-ref.stderr b/tests/ui/binop/binary-op-on-double-ref.stderr
index 34826d2f4bf..2e8aeebc681 100644
--- a/tests/ui/binop/binary-op-on-double-ref.stderr
+++ b/tests/ui/binop/binary-op-on-double-ref.stderr
@@ -1,4 +1,4 @@
-error[E0369]: cannot mod `&&{integer}` by `{integer}`
+error[E0369]: cannot calculate the remainder of `&&{integer}` divided by `{integer}`
   --> $DIR/binary-op-on-double-ref.rs:5:11
    |
 LL |         x % 2 == 0
diff --git a/tests/ui/binop/issue-28837.rs b/tests/ui/binop/issue-28837.rs
index 9719c3afa68..54c8838e48f 100644
--- a/tests/ui/binop/issue-28837.rs
+++ b/tests/ui/binop/issue-28837.rs
@@ -11,7 +11,7 @@ fn main() {
 
     a / a; //~ ERROR cannot divide `A` by `A`
 
-    a % a; //~ ERROR cannot mod `A` by `A`
+    a % a; //~ ERROR cannot calculate the remainder of `A` divided by `A`
 
     a & a; //~ ERROR no implementation for `A & A`
 
diff --git a/tests/ui/binop/issue-28837.stderr b/tests/ui/binop/issue-28837.stderr
index 6e236ca5296..cca1da3b6ac 100644
--- a/tests/ui/binop/issue-28837.stderr
+++ b/tests/ui/binop/issue-28837.stderr
@@ -62,7 +62,7 @@ LL | struct A;
 note: the trait `Div` must be implemented
   --> $SRC_DIR/core/src/ops/arith.rs:LL:COL
 
-error[E0369]: cannot mod `A` by `A`
+error[E0369]: cannot calculate the remainder of `A` divided by `A`
   --> $DIR/issue-28837.rs:14:7
    |
 LL |     a % a;