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.

compiler/rustc_hir_typeck/src/op.rs

@@ -335,7 +335,9 @@ fn check_overloaded_binop(
                                 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}`")

library/core/src/ops/arith.rs

@@ -545,7 +545,7 @@ fn div(self, other: $t) -> $t { self / other }
 #[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 @@ fn div_assign(&mut self, other: $t) { *self /= other }
 #[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 = "%")]

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);
 }

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);
 }

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

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`
 

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;