Make error message for missing fields with .. and without .. more consistent

Author: compiler-errors

compiler/rustc_hir_typeck/src/expr.rs

@@ -2204,8 +2204,12 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 let fields = listify(&missing_mandatory_fields, |f| format!("`{f}`")).unwrap();
                 self.dcx()
                     .struct_span_err(
-                        span.shrink_to_hi(),
-                        format!("missing mandatory field{s} {fields}"),
+                        span.shrink_to_lo(),
+                        format!("missing field{s} {fields} in initializer"),
+                    )
+                    .with_span_label(
+                        span.shrink_to_lo(),
+                        "fields that do not have a defaulted value must be provided explicitly",
                     )
                     .emit();
                 return;

tests/ui/structs/default-field-values/failures.rs

@@ -1,4 +1,4 @@
-#![feature(default_field_values)]
+ #![feature(default_field_values)]
 
 #[derive(Debug)]
 pub struct S;
@@ -50,7 +50,7 @@ enum E {
 fn main () {
     let _ = Foo { .. }; // ok
     let _ = Foo::default(); // ok
-    let _ = Bar { .. }; //~ ERROR mandatory field
+    let _ = Bar { .. }; //~ ERROR missing field
     let _ = Bar::default(); // silenced
     let _ = Bar { bar: S, .. }; // ok
     let _ = Qux::<4> { .. };

tests/ui/structs/default-field-values/failures.stderr

@@ -27,11 +27,11 @@ LL + #[derive(Default)]
 LL | pub struct S;
    |
 
-error: missing mandatory field `bar`
-  --> $DIR/failures.rs:53:21
+error: missing field `bar` in initializer
+  --> $DIR/failures.rs:53:19
    |
 LL |     let _ = Bar { .. };
-   |                     ^
+   |                   ^ fields that do not have a defaulted value must be provided explicitly
 
 error[E0308]: mismatched types
   --> $DIR/failures.rs:57:17