Change some helps to suggestions

2 files changed, 13 insertions, 1 deletions

diff --git a/src/librustc_errors/diagnostic.rs b/src/librustc_errors/diagnostic.rs
index d7c21127474..ee07b6e909f 100644
--- a/src/librustc_errors/diagnostic.rs
+++ b/src/librustc_errors/diagnostic.rs
@@ -211,6 +211,18 @@ impl Diagnostic {
 
     /// Prints out a message with a suggested edit of the code.
     ///
+    /// In case of short messages and a simple suggestion,
+    /// rustc displays it as a label like
+    ///
+    /// "try adding parentheses: `(tup.0).1`"
+    ///
+    /// The message
+    /// * should not end in any punctuation (a `:` is added automatically)
+    /// * should not be a question
+    /// * should not contain any parts like "the following", "as shown"
+    /// * may look like "to do xyz, use" or "to do xyz, use abc"
+    /// * may contain a name of a function, variable or type, but not whole expressions
+    ///
     /// See `diagnostic::CodeSuggestion` for more information.
     pub fn span_suggestion(&mut self, sp: Span, msg: &str, suggestion: String) -> &mut Self {
         self.suggestions.push(CodeSuggestion {
diff --git a/src/librustc_errors/emitter.rs b/src/librustc_errors/emitter.rs
index 2aea6d125f2..3e8bd093f4f 100644
--- a/src/librustc_errors/emitter.rs
+++ b/src/librustc_errors/emitter.rs
@@ -51,7 +51,7 @@ impl Emitter for EmitterWriter {
                     // This substitution is only removal, don't show it
                     format!("help: {}", sugg.msg)
                 } else {
-                    format!("help: {} `{}`", sugg.msg, substitution)
+                    format!("help: {}: `{}`", sugg.msg, substitution)
                 };
                 primary_span.push_span_label(sugg.substitution_spans().next().unwrap(), msg);
             } else {