Make std:: prefix suggestion test run-rustfix

src/test/ui/suggestions/suggest-std-when-using-type.fixed

@@ -0,0 +1,8 @@
+// run-rustfix
+fn main() {
+    let pi = std::f32::consts::PI; //~ ERROR ambiguous associated type
+    let bytes = "hello world".as_bytes();
+    let string = std::str::from_utf8(bytes).unwrap();
+    //~^ ERROR no function or associated item named `from_utf8` found
+    println!("{pi} {bytes:?} {string}");
+}

src/test/ui/suggestions/suggest-std-when-using-type.rs

@@ -1,7 +1,8 @@
+// run-rustfix
 fn main() {
     let pi = f32::consts::PI; //~ ERROR ambiguous associated type
     let bytes = "hello world".as_bytes();
-    let string = unsafe {
-        str::from_utf8(bytes) //~ ERROR no function or associated item named `from_utf8` found
-    };
+    let string = str::from_utf8(bytes).unwrap();
+    //~^ ERROR no function or associated item named `from_utf8` found
+    println!("{pi} {bytes:?} {string}");
 }

src/test/ui/suggestions/suggest-std-when-using-type.stderr

@@ -1,5 +1,5 @@
 error[E0223]: ambiguous associated type
-  --> $DIR/suggest-std-when-using-type.rs:2:14
+  --> $DIR/suggest-std-when-using-type.rs:3:14
    |
 LL |     let pi = f32::consts::PI;
    |              ^^^^^^^^^^^
@@ -10,15 +10,15 @@ LL |     let pi = std::f32::consts::PI;
    |              +++++
 
 error[E0599]: no function or associated item named `from_utf8` found for type `str` in the current scope
-  --> $DIR/suggest-std-when-using-type.rs:5:14
+  --> $DIR/suggest-std-when-using-type.rs:5:23
    |
-LL |         str::from_utf8(bytes)
-   |              ^^^^^^^^^ function or associated item not found in `str`
+LL |     let string = str::from_utf8(bytes).unwrap();
+   |                       ^^^^^^^^^ function or associated item not found in `str`
    |
 help: you are looking for the module in `std`, not the primitive type
    |
-LL |         std::str::from_utf8(bytes)
-   |         +++++
+LL |     let string = std::str::from_utf8(bytes).unwrap();
+   |                  +++++
 
 error: aborting due to 2 previous errors