More accurate incorrect use of await suggestion

compiler/rustc_parse/messages.ftl

@@ -323,10 +323,10 @@ parse_incorrect_semicolon =
     .suggestion = remove this semicolon
     .help = {$name} declarations are not followed by a semicolon
 
-parse_incorrect_use_of_await =
-    incorrect use of `await`
+parse_incorrect_use_of_await = incorrect use of `await`
     .parentheses_suggestion = `await` is not a method call, remove the parentheses
-    .postfix_suggestion = `await` is a postfix operation
+
+parse_incorrect_use_of_await_postfix_suggestion = `await` is a postfix operation
 
 parse_incorrect_visibility_restriction = incorrect visibility restriction
     .help = some possible visibility restrictions are:

compiler/rustc_parse/src/errors.rs

@@ -103,19 +103,26 @@ pub(crate) struct IncorrectUseOfAwait {
     pub span: Span,
 }
 
+#[derive(Subdiagnostic)]
+#[multipart_suggestion(
+    parse_incorrect_use_of_await_postfix_suggestion,
+    applicability = "machine-applicable"
+)]
+pub(crate) struct AwaitSuggestion {
+    #[suggestion_part(code = "")]
+    pub removal: Span,
+    #[suggestion_part(code = ".await{question_mark}")]
+    pub dot_await: Span,
+    pub question_mark: &'static str,
+}
+
 #[derive(Diagnostic)]
 #[diag(parse_incorrect_use_of_await)]
 pub(crate) struct IncorrectAwait {
     #[primary_span]
     pub span: Span,
-    #[suggestion(
-        parse_postfix_suggestion,
-        style = "verbose",
-        code = "{expr}.await{question_mark}"
-    )]
-    pub sugg_span: (Span, Applicability),
-    pub expr: String,
-    pub question_mark: &'static str,
+    #[subdiagnostic]
+    pub suggestion: AwaitSuggestion,
 }
 
 #[derive(Diagnostic)]

compiler/rustc_parse/src/parser/diagnostics.rs

@@ -3,8 +3,8 @@ use super::{
     BlockMode, CommaRecoveryMode, Parser, PathStyle, Restrictions, SemiColonMode, SeqSep, TokenType,
 };
 use crate::errors::{
-    AddParen, AmbiguousPlus, AsyncMoveBlockIn2015, AttributeOnParamType, BadQPathStage2,
-    BadTypePlus, BadTypePlusSub, ColonAsSemi, ComparisonOperatorsCannotBeChained,
+    AddParen, AmbiguousPlus, AsyncMoveBlockIn2015, AttributeOnParamType, AwaitSuggestion,
+    BadQPathStage2, BadTypePlus, BadTypePlusSub, ColonAsSemi, ComparisonOperatorsCannotBeChained,
     ComparisonOperatorsCannotBeChainedSugg, ConstGenericWithoutBraces,
     ConstGenericWithoutBracesSugg, DocCommentDoesNotDocumentAnything, DocCommentOnParamType,
     DoubleColonInBound, ExpectedIdentifier, ExpectedSemi, ExpectedSemiSugg,
@@ -1959,18 +1959,14 @@ impl<'a> Parser<'a> {
         is_question: bool,
     ) -> (Span, ErrorGuaranteed) {
         let span = lo.to(hi);
-        let applicability = match expr.kind {
-            ExprKind::Try(_) => Applicability::MaybeIncorrect, // `await <expr>?`
-            _ => Applicability::MachineApplicable,
-        };
-
         let guar = self.dcx().emit_err(IncorrectAwait {
             span,
-            sugg_span: (span, applicability),
-            expr: self.span_to_snippet(expr.span).unwrap_or_else(|_| pprust::expr_to_string(expr)),
-            question_mark: if is_question { "?" } else { "" },
+            suggestion: AwaitSuggestion {
+                removal: lo.until(expr.span),
+                dot_await: expr.span.shrink_to_hi(),
+                question_mark: if is_question { "?" } else { "" },
+            },
         });
-
         (span, guar)
     }