make suggestion text more legible

Author: Young-Flash

compiler/rustc_resolve/src/late/diagnostics.rs

@@ -1970,7 +1970,7 @@ impl<'a: 'ast, 'ast, 'tcx> LateResolutionVisitor<'a, '_, 'ast, 'tcx> {
         {
             if !ident_span.from_expansion() {
                 let (span, text) = match self.r.tcx.sess.source_map().span_to_snippet(ident_span) {
-                    Ok(var_name) => {
+                    Ok(var_name) if var_name.starts_with("let") => {
                         // a special case for #117894
                         let text = var_name.strip_prefix("let").and_then(|rest| {
                             match rest.starts_with("_") {

tests/ui/suggestions/suggest-let-for-assignment.stderr

@@ -7,7 +7,7 @@ LL |     demo = 1;
 help: you might have meant to introduce a new binding
    |
 LL |     let demo = 1;
-   |     ~~~~~~~~
+   |     +++
 
 error[E0425]: cannot find value `demo` in this scope
   --> $DIR/suggest-let-for-assignment.rs:5:10
@@ -24,7 +24,7 @@ LL |     x = "x";
 help: you might have meant to introduce a new binding
    |
 LL |     let x = "x";
-   |     ~~~~~
+   |     +++
 
 error[E0425]: cannot find value `x` in this scope
   --> $DIR/suggest-let-for-assignment.rs:8:23
@@ -81,7 +81,7 @@ LL |     y = 1 + 2;
 help: you might have meant to introduce a new binding
    |
 LL |     let y = 1 + 2;
-   |     ~~~~~
+   |     +++
 
 error[E0425]: cannot find value `y` in this scope
   --> $DIR/suggest-let-for-assignment.rs:22:23