Update error message E0384 to new format

Part of #35233
Fixes #35184

src/librustc_borrowck/borrowck/mod.rs

@@ -758,12 +758,16 @@ impl<'a, 'tcx> BorrowckCtxt<'a, 'tcx> {
                                                 lp: &LoanPath<'tcx>,
                                                 assign:
                                                 &move_data::Assignment) {
-        struct_span_err!(
+        let mut err = struct_span_err!(
             self.tcx.sess, span, E0384,
             "re-assignment of immutable variable `{}`",
-            self.loan_path_to_string(lp))
-            .span_note(assign.span, "prior assignment occurs here")
-            .emit();
+            self.loan_path_to_string(lp));
+        err.span_label(span, &format!("re-assignment of immutable variable"));
+        if span != assign.span {
+            err.span_label(assign.span, &format!("first assignment to `{}`",
+                                              self.loan_path_to_string(lp)));
+        }
+        err.emit();
     }
 
     pub fn span_err(&self, s: Span, m: &str) {

src/test/compile-fail/asm-out-assign-imm.rs

@@ -18,11 +18,12 @@ fn foo(x: isize) { println!("{}", x); }
           target_arch = "aarch64"))]
 pub fn main() {
     let x: isize;
-    x = 1; //~ NOTE prior assignment occurs here
+    x = 1; //~ NOTE first assignment
     foo(x);
     unsafe {
         asm!("mov $1, $0" : "=r"(x) : "r"(5));
         //~^ ERROR re-assignment of immutable variable `x`
+        //~| NOTE re-assignment of immutable
         //~| NOTE in this expansion of asm!
     }
     foo(x);

src/test/compile-fail/assign-imm-local-twice.rs

@@ -10,9 +10,10 @@
 
 fn test() {
     let v: isize;
-    v = 1; //~ NOTE prior assignment occurs here
+    v = 1; //~ NOTE first assignment
     println!("v={}", v);
     v = 2; //~ ERROR re-assignment of immutable variable
+           //~| NOTE re-assignment of immutable
     println!("v={}", v);
 }
 

src/test/compile-fail/liveness-assign-imm-local-in-loop.rs

@@ -12,7 +12,7 @@ fn test() {
     let v: isize;
     loop {
         v = 1; //~ ERROR re-assignment of immutable variable
-        //~^ NOTE prior assignment occurs here
+        //~^ NOTE re-assignment of immutable variable
         v.clone(); // just to prevent liveness warnings
     }
 }

src/test/compile-fail/liveness-assign-imm-local-in-op-eq.rs

@@ -10,8 +10,9 @@
 
 fn test() {
     let v: isize;
-    v = 2;  //~ NOTE prior assignment occurs here
+    v = 2;  //~ NOTE first assignment
     v += 1; //~ ERROR re-assignment of immutable variable
+            //~| NOTE re-assignment of immutable
     v.clone();
 }
 

src/test/compile-fail/liveness-assign-imm-local-with-init.rs

@@ -9,9 +9,10 @@
 // except according to those terms.
 
 fn test() {
-    let v: isize = 1; //~ NOTE prior assignment occurs here
+    let v: isize = 1; //~ NOTE first assignment
     v.clone();
     v = 2; //~ ERROR re-assignment of immutable variable
+           //~| NOTE re-assignment of immutable
     v.clone();
 }