Rollup merge of #101424 - compiler-errors:operator-err-sugg, r=TaKO8Ki

Adjust and slightly generalize operator error suggestion

(in no particular order)
* Stop passing around a whole extra `ProjectionPredicate`
* Add spaces around `=` in `Trait<..., Output = Ty>` suggestion
* Some code clean-ups, including
    * add `lang_item_for_op` to turn a `Op` into a `DefId`
    * avoid `SourceMap` because we don't really need to render an expr
    * Remove `TypeParamVisitor` in favor of just checking `ty.has_param_types_or_consts` -- this acts a bit differently, but shouldn't cause erroneous suggestions (actually might generalize them a bit)
* We now suggest `Output = Ty` in the `where` clause suggestion when we fail to add `Struct<T>` and `T`.

I can split this out into more PRs if needed, but they're all just miscellaneous generalizations, changes, and nitpicks I saw when messing with this operator code.

10 files changed, 51 insertions, 13 deletions

diff --git a/src/test/ui/binop/binary-op-on-double-ref.stderr b/src/test/ui/binop/binary-op-on-double-ref.stderr
index 1651f70d5cd..34826d2f4bf 100644
--- a/src/test/ui/binop/binary-op-on-double-ref.stderr
+++ b/src/test/ui/binop/binary-op-on-double-ref.stderr
@@ -6,7 +6,7 @@ LL |         x % 2 == 0
    |         |
    |         &&{integer}
    |
-help: `%` can be used on `{integer}`, you can dereference `x`
+help: `%` can be used on `&{integer}` if you dereference the left-hand side
    |
 LL |         *x % 2 == 0
    |         +
diff --git a/src/test/ui/generic-associated-types/missing-bounds.fixed b/src/test/ui/generic-associated-types/missing-bounds.fixed
index 2315810a47a..ee758f19ec1 100644
--- a/src/test/ui/generic-associated-types/missing-bounds.fixed
+++ b/src/test/ui/generic-associated-types/missing-bounds.fixed
@@ -24,7 +24,7 @@ impl<B: Add + Add<Output = B>> Add for C<B> {
 
 struct D<B>(B);
 
-impl<B: std::ops::Add<Output=B>> Add for D<B> {
+impl<B: std::ops::Add<Output = B>> Add for D<B> {
     type Output = Self;
 
     fn add(self, rhs: Self) -> Self {
diff --git a/src/test/ui/generic-associated-types/missing-bounds.stderr b/src/test/ui/generic-associated-types/missing-bounds.stderr
index 138c642dd79..c913483a874 100644
--- a/src/test/ui/generic-associated-types/missing-bounds.stderr
+++ b/src/test/ui/generic-associated-types/missing-bounds.stderr
@@ -66,8 +66,8 @@ LL |         Self(self.0 + rhs.0)
    |
 help: consider restricting type parameter `B`
    |
-LL | impl<B: std::ops::Add<Output=B>> Add for D<B> {
-   |       +++++++++++++++++++++++++
+LL | impl<B: std::ops::Add<Output = B>> Add for D<B> {
+   |       +++++++++++++++++++++++++++
 
 error[E0308]: mismatched types
   --> $DIR/missing-bounds.rs:42:14
diff --git a/src/test/ui/suggestions/issue-97677.fixed b/src/test/ui/suggestions/issue-97677.fixed
index 73ca9f97b43..1e7569fa451 100644
--- a/src/test/ui/suggestions/issue-97677.fixed
+++ b/src/test/ui/suggestions/issue-97677.fixed
@@ -1,6 +1,6 @@
 // run-rustfix
 
-fn add_ten<N: std::ops::Add<i32, Output=N>>(n: N) -> N {
+fn add_ten<N: std::ops::Add<i32, Output = N>>(n: N) -> N {
     n + 10
     //~^ ERROR cannot add `{integer}` to `N`
 }
diff --git a/src/test/ui/suggestions/issue-97677.stderr b/src/test/ui/suggestions/issue-97677.stderr
index 069b184ac63..575d79267f2 100644
--- a/src/test/ui/suggestions/issue-97677.stderr
+++ b/src/test/ui/suggestions/issue-97677.stderr
@@ -8,8 +8,8 @@ LL |     n + 10
    |
 help: consider restricting type parameter `N`
    |
-LL | fn add_ten<N: std::ops::Add<i32, Output=N>>(n: N) -> N {
-   |             ++++++++++++++++++++++++++++++
+LL | fn add_ten<N: std::ops::Add<i32, Output = N>>(n: N) -> N {
+   |             ++++++++++++++++++++++++++++++++
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/suggestions/restrict-type-not-param.rs b/src/test/ui/suggestions/restrict-type-not-param.rs
new file mode 100644
index 00000000000..60f5ba45c26
--- /dev/null
+++ b/src/test/ui/suggestions/restrict-type-not-param.rs
@@ -0,0 +1,12 @@
+use std::ops::Add;
+
+struct Wrapper<T>(T);
+
+trait Foo {}
+
+fn qux<T>(a: Wrapper<T>, b: T) -> T {
+    a + b
+    //~^ ERROR cannot add `T` to `Wrapper<T>`
+}
+
+fn main() {}
diff --git a/src/test/ui/suggestions/restrict-type-not-param.stderr b/src/test/ui/suggestions/restrict-type-not-param.stderr
new file mode 100644
index 00000000000..e7d9c5ecbe4
--- /dev/null
+++ b/src/test/ui/suggestions/restrict-type-not-param.stderr
@@ -0,0 +1,26 @@
+error[E0369]: cannot add `T` to `Wrapper<T>`
+  --> $DIR/restrict-type-not-param.rs:8:7
+   |
+LL |     a + b
+   |     - ^ - T
+   |     |
+   |     Wrapper<T>
+   |
+note: an implementation of `Add<_>` might be missing for `Wrapper<T>`
+  --> $DIR/restrict-type-not-param.rs:3:1
+   |
+LL | struct Wrapper<T>(T);
+   | ^^^^^^^^^^^^^^^^^ must implement `Add<_>`
+note: the following trait must be implemented
+  --> $SRC_DIR/core/src/ops/arith.rs:LL:COL
+   |
+LL | pub trait Add<Rhs = Self> {
+   | ^^^^^^^^^^^^^^^^^^^^^^^^^
+help: consider introducing a `where` clause, but there might be an alternative better way to express this requirement
+   |
+LL | fn qux<T>(a: Wrapper<T>, b: T) -> T where Wrapper<T>: Add<T, Output = T> {
+   |                                     ++++++++++++++++++++++++++++++++++++
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0369`.
diff --git a/src/test/ui/traits/resolution-in-overloaded-op.stderr b/src/test/ui/traits/resolution-in-overloaded-op.stderr
index 34fae64e4d2..fe5e1d6d285 100644
--- a/src/test/ui/traits/resolution-in-overloaded-op.stderr
+++ b/src/test/ui/traits/resolution-in-overloaded-op.stderr
@@ -8,8 +8,8 @@ LL |     a * b
    |
 help: consider introducing a `where` clause, but there might be an alternative better way to express this requirement
    |
-LL | fn foo<T: MyMul<f64, f64>>(a: &T, b: f64) -> f64 where &T: Mul<f64> {
-   |                                                  ++++++++++++++++++
+LL | fn foo<T: MyMul<f64, f64>>(a: &T, b: f64) -> f64 where &T: Mul<f64, Output = f64> {
+   |                                                  ++++++++++++++++++++++++++++++++
 
 error: aborting due to previous error
 
diff --git a/src/test/ui/typeck/assign-non-lval-derefmut.stderr b/src/test/ui/typeck/assign-non-lval-derefmut.stderr
index a6fcdfe21f4..e394cf8206e 100644
--- a/src/test/ui/typeck/assign-non-lval-derefmut.stderr
+++ b/src/test/ui/typeck/assign-non-lval-derefmut.stderr
@@ -19,7 +19,7 @@ LL |     x.lock().unwrap() += 1;
    |     |
    |     cannot use `+=` on type `MutexGuard<'_, usize>`
    |
-help: `+=` can be used on `usize`, you can dereference `x.lock().unwrap()`
+help: `+=` can be used on `usize` if you dereference the left-hand side
    |
 LL |     *x.lock().unwrap() += 1;
    |     +
@@ -47,7 +47,7 @@ LL |     y += 1;
    |     |
    |     cannot use `+=` on type `MutexGuard<'_, usize>`
    |
-help: `+=` can be used on `usize`, you can dereference `y`
+help: `+=` can be used on `usize` if you dereference the left-hand side
    |
 LL |     *y += 1;
    |     +
diff --git a/src/test/ui/typeck/assign-non-lval-mut-ref.stderr b/src/test/ui/typeck/assign-non-lval-mut-ref.stderr
index be2e9fe95e8..cbdc960baab 100644
--- a/src/test/ui/typeck/assign-non-lval-mut-ref.stderr
+++ b/src/test/ui/typeck/assign-non-lval-mut-ref.stderr
@@ -19,7 +19,7 @@ LL |     x.last_mut().unwrap() += 1;
    |     |
    |     cannot use `+=` on type `&mut usize`
    |
-help: `+=` can be used on `usize`, you can dereference `x.last_mut().unwrap()`
+help: `+=` can be used on `usize` if you dereference the left-hand side
    |
 LL |     *x.last_mut().unwrap() += 1;
    |     +
@@ -45,7 +45,7 @@ LL |     y += 1;
    |     |
    |     cannot use `+=` on type `&mut usize`
    |
-help: `+=` can be used on `usize`, you can dereference `y`
+help: `+=` can be used on `usize` if you dereference the left-hand side
    |
 LL |     *y += 1;
    |     +