Avoid suggesting literal formatting that turns into member access

compiler/rustc_typeck/src/check/method/suggest.rs

@@ -317,14 +317,18 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
  .span_to_snippet(lit.span)
  .unwrap_or_else(|_| "<numeric literal>".to_owned());
 
+ // If this is a floating point literal that ends with '.',
+ // get rid of it to stop this from becoming a member access.
+ let snippet = snippet.strip_suffix('.').unwrap_or(&snippet);
+
  err.span_suggestion(
  lit.span,
  &format!(
  "you must specify a concrete type for this numeric value, \
  like `{}`",
  concrete_type
  ),
- format!("{}_{}", snippet, concrete_type),
+ format!("{snippet}_{concrete_type}"),
  Applicability::MaybeIncorrect,
  );
  }

src/test/ui/suggestions/issue-90974.rs

@@ -0,0 +1,3 @@
+fn main() {
+ println!("{}", (3.).recip()); //~ERROR
+}

src/test/ui/suggestions/issue-90974.stderr

@@ -0,0 +1,14 @@
+error[E0689]: can't call method `recip` on ambiguous numeric type `{float}`
+ --> $DIR/issue-90974.rs:2:25
+ |
+LL | println!("{}", (3.).recip());
+ | ^^^^^
+ |
+help: you must specify a concrete type for this numeric value, like `f32`
+ |
+LL | println!("{}", (3_f32).recip());
+ | ~~~~~
+
+error: aborting due to previous error
+
+For more information about this error, try `rustc --explain E0689`.