Fixed missing newline on each field on "Missing structure fields".

Author: flipbit03

crates/ra_hir_ty/src/diagnostics.rs

@@ -40,7 +40,7 @@ impl Diagnostic for MissingFields {
     fn message(&self) -> String {
         let mut buf = String::from("Missing structure fields:\n");
         for field in &self.missed_fields {
-            format_to!(buf, "- {}", field);
+            format_to!(buf, "- {}\n", field);
         }
         buf
     }
@@ -73,7 +73,7 @@ impl Diagnostic for MissingPatFields {
     fn message(&self) -> String {
         let mut buf = String::from("Missing structure fields:\n");
         for field in &self.missed_fields {
-            format_to!(buf, "- {}", field);
+            format_to!(buf, "- {}\n", field);
         }
         buf
     }

crates/ra_ide/src/diagnostics.rs

@@ -664,7 +664,7 @@ mod tests {
         assert_debug_snapshot!(diagnostics, @r###"
         [
             Diagnostic {
-                message: "Missing structure fields:\n- b",
+                message: "Missing structure fields:\n- b\n",
                 range: 224..233,
                 severity: Error,
                 fix: Some(