Use smaller spans for some structured suggestions

Use more accurate suggestion spans for

* argument parse error
* fully qualified path
* missing code block type
* numeric casts
* E0212

Author: estebank

compiler/rustc_errors/src/diagnostic.rs

@@ -298,6 +298,21 @@ impl Diagnostic {
         )
     }
 
+    /// Show a suggestion that has multiple parts to it, always as it's own subdiagnostic.
+    /// In other words, multiple changes need to be applied as part of this suggestion.
+    pub fn multipart_suggestion_verbose(
+        &mut self,
+        msg: &str,
+        suggestion: Vec<(Span, String)>,
+        applicability: Applicability,
+    ) -> &mut Self {
+        self.multipart_suggestion_with_style(
+            msg,
+            suggestion,
+            applicability,
+            SuggestionStyle::ShowAlways,
+        )
+    }
     /// [`Diagnostic::multipart_suggestion()`] but you can set the [`SuggestionStyle`].
     pub fn multipart_suggestion_with_style(
         &mut self,

compiler/rustc_errors/src/diagnostic_builder.rs

@@ -257,6 +257,20 @@ impl<'a> DiagnosticBuilder<'a> {
         self
     }
 
+    /// See [`Diagnostic::multipart_suggestion()`].
+    pub fn multipart_suggestion_verbose(
+        &mut self,
+        msg: &str,
+        suggestion: Vec<(Span, String)>,
+        applicability: Applicability,
+    ) -> &mut Self {
+        if !self.0.allow_suggestions {
+            return self;
+        }
+        self.0.diagnostic.multipart_suggestion_verbose(msg, suggestion, applicability);
+        self
+    }
+
     /// See [`Diagnostic::tool_only_multipart_suggestion()`].
     pub fn tool_only_multipart_suggestion(
         &mut self,