Adjust spacing in suggestion, add a test

compiler/rustc_middle/src/ty/diagnostics.rs

@@ -115,9 +115,9 @@ pub fn suggest_arbitrary_trait_bound<'tcx>(
         // FIXME: this case overlaps with code in TyCtxt::note_and_explain_type_err.
         // That should be extracted into a helper function.
         if constraint.ends_with('>') {
-            constraint = format!("{}, {}={}>", &constraint[..constraint.len() - 1], name, term);
+            constraint = format!("{}, {} = {}>", &constraint[..constraint.len() - 1], name, term);
         } else {
-            constraint.push_str(&format!("<{}={}>", name, term));
+            constraint.push_str(&format!("<{} = {}>", name, term));
         }
     }
 

compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs

@@ -608,13 +608,13 @@ impl<'a, 'tcx> InferCtxtExt<'tcx> for InferCtxt<'a, 'tcx> {
                         // That should be extracted into a helper function.
                         if constraint.ends_with('>') {
                             constraint = format!(
-                                "{}, {}={}>",
+                                "{}, {} = {}>",
                                 &constraint[..constraint.len() - 1],
                                 name,
                                 term
                             );
                         } else {
-                            constraint.push_str(&format!("<{}={}>", name, term));
+                            constraint.push_str(&format!("<{} = {}>", name, term));
                         }
                     }
 

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 {

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

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`
 }

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
 

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() {}

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`.

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, Output=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