Auto merge of #138271 - mu001999-contrib:fix-138234, r=jackh726

Keep space if arg does not follow punctuation when lint unused parens

Fixes rust-lang/rust#138234

If the arg follows punctuation, still pass `left_pos` with `None` and no space will be added, else then pass `left_pos` with `Some(arg.span.lo())`, so that we can add the space as expected.

And `emit_unused_delims` can make sure no more space will be added if the expr follows space.

---

Edited:

Directly use the `value_span` to check whether the expr removed parens will follow identifier or be followed by identifier.

1 files changed, 8 insertions, 0 deletions

diff --git a/compiler/rustc_lint/src/unused.rs b/compiler/rustc_lint/src/unused.rs
index 22d89d24612..edbbfba4f34 100644
--- a/compiler/rustc_lint/src/unused.rs
+++ b/compiler/rustc_lint/src/unused.rs
@@ -843,6 +843,10 @@ trait UnusedDelimLint {
                 && !snip.ends_with(' ')
             {
                 " "
+            } else if let Ok(snip) = sm.span_to_prev_source(value_span)
+                && snip.ends_with(|c: char| c.is_alphanumeric())
+            {
+                " "
             } else {
                 ""
             };
@@ -852,6 +856,10 @@ trait UnusedDelimLint {
                 && !snip.starts_with(' ')
             {
                 " "
+            } else if let Ok(snip) = sm.span_to_prev_source(value_span)
+                && snip.starts_with(|c: char| c.is_alphanumeric())
+            {
+                " "
             } else {
                 ""
             };