From a7261c32f485872756b8dc1544963a59e86c6449 Mon Sep 17 00:00:00 2001
From: Michael Howell <michael@notriddle.com>
Date: Wed, 17 Nov 2021 13:28:54 -0700
Subject: [PATCH] Avoid suggesting literal formatting that turns into member
 access

Fixes #90974
---
 compiler/rustc_typeck/src/check/method/suggest.rs |  6 +++++-
 src/test/ui/suggestions/issue-90974.rs            |  3 +++
 src/test/ui/suggestions/issue-90974.stderr        | 14 ++++++++++++++
 3 files changed, 22 insertions(+), 1 deletion(-)
 create mode 100644 src/test/ui/suggestions/issue-90974.rs
 create mode 100644 src/test/ui/suggestions/issue-90974.stderr

diff --git a/compiler/rustc_typeck/src/check/method/suggest.rs b/compiler/rustc_typeck/src/check/method/suggest.rs
index 71cd8a43329c5..aceeb924ac4ad 100644
--- a/compiler/rustc_typeck/src/check/method/suggest.rs
+++ b/compiler/rustc_typeck/src/check/method/suggest.rs
@@ -317,6 +317,10 @@ 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!(
@@ -324,7 +328,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                                          like `{}`",
                                         concrete_type
                                     ),
-                                    format!("{}_{}", snippet, concrete_type),
+                                    format!("{snippet}_{concrete_type}"),
                                     Applicability::MaybeIncorrect,
                                 );
                             }
diff --git a/src/test/ui/suggestions/issue-90974.rs b/src/test/ui/suggestions/issue-90974.rs
new file mode 100644
index 0000000000000..83590dbf7ace7
--- /dev/null
+++ b/src/test/ui/suggestions/issue-90974.rs
@@ -0,0 +1,3 @@
+fn main() {
+    println!("{}", (3.).recip()); //~ERROR
+}
diff --git a/src/test/ui/suggestions/issue-90974.stderr b/src/test/ui/suggestions/issue-90974.stderr
new file mode 100644
index 0000000000000..e1fb479a3a7a0
--- /dev/null
+++ b/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`.