Rollup merge of #124000 - compiler-errors:sugg-tweaks, r=wesleywiser

GuillaumeGomez · web-flow · commit 4764dceb0f6f · 2024-04-17T00:00:23.000+02:00
Use `/* value */` as a placeholder

The expression `value` isn't a valid suggestion; let's use `/* value */` as a placeholder (which is also invalid) since it more clearly signals to the user that they need to fill it in with something meaningful. This parallels the suggestions we have in a couple other places, like arguments.

We could also print the type name instead of `/* value */`, especially if it's suggestable, but I don't care strongly about that.
diff --git a/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs b/compiler/rustc_trait_selection/src/traits/error_reporting/suggestions.rs
@@ -4545,7 +4545,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
             self.type_implements_trait(default_trait, [ty], param_env).must_apply_modulo_regions()
         };
 
-        Some(match ty.kind() {
+        Some(match *ty.kind() {
             ty::Never | ty::Error(_) => return None,
             ty::Bool => "false".to_string(),
             ty::Char => "\'x\'".to_string(),
@@ -4572,12 +4572,19 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                 if let (ty::Str, hir::Mutability::Not) = (ty.kind(), mutability) {
                     "\"\"".to_string()
                 } else {
-                    let ty = self.ty_kind_suggestion(param_env, *ty)?;
+                    let ty = self.ty_kind_suggestion(param_env, ty)?;
                     format!("&{}{ty}", mutability.prefix_str())
                 }
             }
             ty::Array(ty, len) if let Some(len) = len.try_eval_target_usize(tcx, param_env) => {
-                format!("[{}; {}]", self.ty_kind_suggestion(param_env, *ty)?, len)
+                if len == 0 {
+                    "[]".to_string()
+                } else if self.type_is_copy_modulo_regions(param_env, ty) || len == 1 {
+                    // Can only suggest `[ty; 0]` if sz == 1 or copy
+                    format!("[{}; {}]", self.ty_kind_suggestion(param_env, ty)?, len)
+                } else {
+                    "/* value */".to_string()
+                }
             }
             ty::Tuple(tys) => format!(
                 "({}{})",
@@ -4587,7 +4594,7 @@ impl<'tcx> TypeErrCtxt<'_, 'tcx> {
                     .join(", "),
                 if tys.len() == 1 { "," } else { "" }
             ),
-            _ => "value".to_string(),
+            _ => "/* value */".to_string(),
         })
     }
 }
diff --git a/tests/ui/borrowck/borrowck-init-in-fru.stderr b/tests/ui/borrowck/borrowck-init-in-fru.stderr
@@ -8,8 +8,8 @@ LL |     origin = Point { x: 10, ..origin };
    |
 help: consider assigning a value
    |
-LL |     let mut origin: Point = value;
-   |                           +++++++
+LL |     let mut origin: Point = /* value */;
+   |                           +++++++++++++
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/borrowck/borrowck-uninit-ref-chain.stderr b/tests/ui/borrowck/borrowck-uninit-ref-chain.stderr
@@ -21,8 +21,8 @@ LL |     let _y = &**x;
    |
 help: consider assigning a value
    |
-LL |     let x: &&S<i32, i32> = &&value;
-   |                          +++++++++
+LL |     let x: &&S<i32, i32> = &&/* value */;
+   |                          +++++++++++++++
 
 error[E0381]: used binding `x` isn't initialized
   --> $DIR/borrowck-uninit-ref-chain.rs:14:14
diff --git a/tests/ui/borrowck/issue-103250.stderr b/tests/ui/borrowck/issue-103250.stderr
@@ -9,8 +9,8 @@ LL |         Err(last_error)
    |
 help: consider assigning a value
    |
-LL |         let mut last_error: Box<dyn std::error::Error> = Box::new(value);
-   |                                                        +++++++++++++++++
+LL |         let mut last_error: Box<dyn std::error::Error> = Box::new(/* value */);
+   |                                                        +++++++++++++++++++++++
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/borrowck/suggest-assign-rvalue.stderr b/tests/ui/borrowck/suggest-assign-rvalue.stderr
@@ -50,8 +50,8 @@ LL |     println!("demo_no: {:?}", demo_no);
    = note: this error originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)
 help: consider assigning a value
    |
-LL |     let demo_no: DemoNoDef = value;
-   |                            +++++++
+LL |     let demo_no: DemoNoDef = /* value */;
+   |                            +++++++++++++
 
 error[E0381]: used binding `arr` isn't initialized
   --> $DIR/suggest-assign-rvalue.rs:34:27
diff --git a/tests/ui/consts/value-suggestion-ice-123906.stderr b/tests/ui/consts/value-suggestion-ice-123906.stderr
@@ -10,8 +10,8 @@ LL |         break;
    |
 help: give the `break` a value of the expected type
    |
-LL |         break value;
-   |               +++++
+LL |         break /* value */;
+   |               +++++++++++
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/loops/loop-break-value.stderr b/tests/ui/loops/loop-break-value.stderr
@@ -246,8 +246,8 @@ LL |         break;
    |
 help: give the `break` a value of the expected type
    |
-LL |         break value;
-   |               +++++
+LL |         break /* value */;
+   |               +++++++++++
 
 error[E0308]: mismatched types
   --> $DIR/loop-break-value.rs:112:9
@@ -260,8 +260,8 @@ LL |         break;
    |
 help: give the `break` a value of the expected type
    |
-LL |         break value;
-   |               +++++
+LL |         break /* value */;
+   |               +++++++++++
 
 error[E0308]: mismatched types
   --> $DIR/loop-break-value.rs:124:9
@@ -274,8 +274,8 @@ LL |         break 'a;
    |
 help: give the `break` a value of the expected type
    |
-LL |         break 'a value;
-   |                  +++++
+LL |         break 'a /* value */;
+   |                  +++++++++++
 
 error[E0308]: mismatched types
   --> $DIR/loop-break-value.rs:135:15
@@ -297,8 +297,8 @@ LL |                 break 'a;
    |
 help: give the `break` a value of the expected type
    |
-LL |                 break 'a value;
-   |                          +++++
+LL |                 break 'a /* value */;
+   |                          +++++++++++
 
 error[E0308]: mismatched types
   --> $DIR/loop-break-value.rs:147:15
@@ -320,8 +320,8 @@ LL |                 break 'a;
    |
 help: give the `break` a value of the expected type
    |
-LL |                 break 'a value;
-   |                          +++++
+LL |                 break 'a /* value */;
+   |                          +++++++++++
 
 error[E0308]: mismatched types
   --> $DIR/loop-break-value.rs:159:15
diff --git a/tests/ui/moves/issue-72649-uninit-in-loop.stderr b/tests/ui/moves/issue-72649-uninit-in-loop.stderr
@@ -80,8 +80,8 @@ LL |         let _used = value;
    |
 help: consider assigning a value
    |
-LL |         let value: NonCopy = value;
-   |                            +++++++
+LL |         let value: NonCopy = /* value */;
+   |                            +++++++++++++
 
 error[E0381]: used binding `value` isn't initialized
   --> $DIR/issue-72649-uninit-in-loop.rs:73:21
@@ -94,8 +94,8 @@ LL |         let _used = value;
    |
 help: consider assigning a value
    |
-LL |     let mut value: NonCopy = value;
-   |                            +++++++
+LL |     let mut value: NonCopy = /* value */;
+   |                            +++++++++++++
 
 error: aborting due to 6 previous errors
 
diff --git a/tests/ui/moves/move-into-dead-array-1.stderr b/tests/ui/moves/move-into-dead-array-1.stderr
@@ -8,8 +8,8 @@ LL |     a[i] = d();
    |
 help: consider assigning a value
    |
-LL |     let mut a: [D; 4] = [value; 4];
-   |                       ++++++++++++
+LL |     let mut a: [D; 4] = /* value */;
+   |                       +++++++++++++
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/moves/move-of-addr-of-mut.stderr b/tests/ui/moves/move-of-addr-of-mut.stderr
@@ -9,8 +9,8 @@ LL |     std::ptr::addr_of_mut!(x);
    = note: this error originates in the macro `std::ptr::addr_of_mut` (in Nightly builds, run with -Z macro-backtrace for more info)
 help: consider assigning a value
    |
-LL |     let mut x: S = value;
-   |                  +++++++
+LL |     let mut x: S = /* value */;
+   |                  +++++++++++++
 
 error: aborting due to 1 previous error
 
diff --git a/tests/ui/nll/match-on-borrowed.stderr b/tests/ui/nll/match-on-borrowed.stderr
@@ -43,8 +43,8 @@ LL |     match n {}
    |
 help: consider assigning a value
    |
-LL |     let n: Never = value;
-   |                  +++++++
+LL |     let n: Never = /* value */;
+   |                  +++++++++++++
 
 error: aborting due to 4 previous errors
 

Original file line number	Diff line number	Diff line change
`@@ -8,8 +8,8 @@ LL \| origin = Point { x: 10, ..origin };`
`8`	`8`	`\|`
`9`	`9`	`help: consider assigning a value`
`10`	`10`	`\|`
`11`		`-LL \| let mut origin: Point = value;`
`12`		`- \| +++++++`
	`11`	`+LL \| let mut origin: Point = /* value */;`
	`12`	`+ \| +++++++++++++`
`13`	`13`
`14`	`14`	`error: aborting due to 1 previous error`
`15`	`15`
Original file line number	Diff line number	Diff line change
`@@ -21,8 +21,8 @@ LL \| let _y = &**x;`
`21`	`21`	`\|`
`22`	`22`	`help: consider assigning a value`
`23`	`23`	`\|`
`24`		`-LL \| let x: &&S<i32, i32> = &&value;`
`25`		`- \| +++++++++`
	`24`	`+LL \| let x: &&S<i32, i32> = &&/* value */;`
	`25`	`+ \| +++++++++++++++`
`26`	`26`
`27`	`27`	error[E0381]: used binding `x` isn't initialized
`28`	`28`	`--> $DIR/borrowck-uninit-ref-chain.rs:14:14`
Original file line number	Diff line number	Diff line change
`@@ -9,8 +9,8 @@ LL \| Err(last_error)`
`9`	`9`	`\|`
`10`	`10`	`help: consider assigning a value`
`11`	`11`	`\|`
`12`		`-LL \| let mut last_error: Box<dyn std::error::Error> = Box::new(value);`
`13`		`- \| +++++++++++++++++`
	`12`	`+LL \| let mut last_error: Box<dyn std::error::Error> = Box::new(/* value */);`
	`13`	`+ \| +++++++++++++++++++++++`
`14`	`14`
`15`	`15`	`error: aborting due to 1 previous error`
`16`	`16`
Original file line number	Diff line number	Diff line change
`@@ -10,8 +10,8 @@ LL \| break;`
`10`	`10`	`\|`
`11`	`11`	help: give the `break` a value of the expected type
`12`	`12`	`\|`
`13`		`-LL \| break value;`
`14`		`- \| +++++`
	`13`	`+LL \| break /* value */;`
	`14`	`+ \| +++++++++++`
`15`	`15`
`16`	`16`	`error: aborting due to 1 previous error`
`17`	`17`
Original file line number	Diff line number	Diff line change
`@@ -246,8 +246,8 @@ LL \| break;`
`246`	`246`	`\|`
`247`	`247`	help: give the `break` a value of the expected type
`248`	`248`	`\|`
`249`		`-LL \| break value;`
`250`		`- \| +++++`
	`249`	`+LL \| break /* value */;`
	`250`	`+ \| +++++++++++`
`251`	`251`
`252`	`252`	`error[E0308]: mismatched types`
`253`	`253`	`--> $DIR/loop-break-value.rs:112:9`
`@@ -260,8 +260,8 @@ LL \| break;`
`260`	`260`	`\|`
`261`	`261`	help: give the `break` a value of the expected type
`262`	`262`	`\|`
`263`		`-LL \| break value;`
`264`		`- \| +++++`
	`263`	`+LL \| break /* value */;`
	`264`	`+ \| +++++++++++`
`265`	`265`
`266`	`266`	`error[E0308]: mismatched types`
`267`	`267`	`--> $DIR/loop-break-value.rs:124:9`
`@@ -274,8 +274,8 @@ LL \| break 'a;`
`274`	`274`	`\|`
`275`	`275`	help: give the `break` a value of the expected type
`276`	`276`	`\|`
`277`		`-LL \| break 'a value;`
`278`		`- \| +++++`
	`277`	`+LL \| break 'a /* value */;`
	`278`	`+ \| +++++++++++`
`279`	`279`
`280`	`280`	`error[E0308]: mismatched types`
`281`	`281`	`--> $DIR/loop-break-value.rs:135:15`
`@@ -297,8 +297,8 @@ LL \| break 'a;`
`297`	`297`	`\|`
`298`	`298`	help: give the `break` a value of the expected type
`299`	`299`	`\|`
`300`		`-LL \| break 'a value;`
`301`		`- \| +++++`
	`300`	`+LL \| break 'a /* value */;`
	`301`	`+ \| +++++++++++`
`302`	`302`
`303`	`303`	`error[E0308]: mismatched types`
`304`	`304`	`--> $DIR/loop-break-value.rs:147:15`
`@@ -320,8 +320,8 @@ LL \| break 'a;`
`320`	`320`	`\|`
`321`	`321`	help: give the `break` a value of the expected type
`322`	`322`	`\|`
`323`		`-LL \| break 'a value;`
`324`		`- \| +++++`
	`323`	`+LL \| break 'a /* value */;`
	`324`	`+ \| +++++++++++`
`325`	`325`
`326`	`326`	`error[E0308]: mismatched types`
`327`	`327`	`--> $DIR/loop-break-value.rs:159:15`
Original file line number	Diff line number	Diff line change
`@@ -80,8 +80,8 @@ LL \| let _used = value;`
`80`	`80`	`\|`
`81`	`81`	`help: consider assigning a value`
`82`	`82`	`\|`
`83`		`-LL \| let value: NonCopy = value;`
`84`		`- \| +++++++`
	`83`	`+LL \| let value: NonCopy = /* value */;`
	`84`	`+ \| +++++++++++++`
`85`	`85`
`86`	`86`	error[E0381]: used binding `value` isn't initialized
`87`	`87`	`--> $DIR/issue-72649-uninit-in-loop.rs:73:21`
`@@ -94,8 +94,8 @@ LL \| let _used = value;`
`94`	`94`	`\|`
`95`	`95`	`help: consider assigning a value`
`96`	`96`	`\|`
`97`		`-LL \| let mut value: NonCopy = value;`
`98`		`- \| +++++++`
	`97`	`+LL \| let mut value: NonCopy = /* value */;`
	`98`	`+ \| +++++++++++++`
`99`	`99`
`100`	`100`	`error: aborting due to 6 previous errors`
`101`	`101`
Original file line number	Diff line number	Diff line change
`@@ -8,8 +8,8 @@ LL \| a[i] = d();`
`8`	`8`	`\|`
`9`	`9`	`help: consider assigning a value`
`10`	`10`	`\|`
`11`		`-LL \| let mut a: [D; 4] = [value; 4];`
`12`		`- \| ++++++++++++`
	`11`	`+LL \| let mut a: [D; 4] = /* value */;`
	`12`	`+ \| +++++++++++++`
`13`	`13`
`14`	`14`	`error: aborting due to 1 previous error`
`15`	`15`
Original file line number	Diff line number	Diff line change
`@@ -9,8 +9,8 @@ LL \| std::ptr::addr_of_mut!(x);`
`9`	`9`	= note: this error originates in the macro `std::ptr::addr_of_mut` (in Nightly builds, run with -Z macro-backtrace for more info)
`10`	`10`	`help: consider assigning a value`
`11`	`11`	`\|`
`12`		`-LL \| let mut x: S = value;`
`13`		`- \| +++++++`
	`12`	`+LL \| let mut x: S = /* value */;`
	`13`	`+ \| +++++++++++++`
`14`	`14`
`15`	`15`	`error: aborting due to 1 previous error`
`16`	`16`
Original file line number	Diff line number	Diff line change
`@@ -43,8 +43,8 @@ LL \| match n {}`
`43`	`43`	`\|`
`44`	`44`	`help: consider assigning a value`
`45`	`45`	`\|`
`46`		`-LL \| let n: Never = value;`
`47`		`- \| +++++++`
	`46`	`+LL \| let n: Never = /* value */;`
	`47`	`+ \| +++++++++++++`
`48`	`48`
`49`	`49`	`error: aborting due to 4 previous errors`
`50`	`50`