fix: between span derviation on cast exprs

Author: calebcartwright

src/formatting/expr.rs

@@ -236,10 +236,10 @@ pub(crate) fn format_expr(
             /* Retrieving the comments before and after cast */
             let prefix_span = mk_sp(
                 subexpr.span.hi(),
-                context.snippet_provider.span_before(expr.span, "as"),
+                context.snippet_provider.span_before_last(expr.span, "as") - BytePos(1),
             );
             let suffix_span = mk_sp(
-                context.snippet_provider.span_after(expr.span, "as"),
+                context.snippet_provider.span_after_last(expr.span, "as"),
                 ty.span.lo(),
             );
             let infix_prefix_comments = rewrite_missing_comment(prefix_span, shape, context)?;

tests/source/issue_4534.rs

@@ -0,0 +1,4 @@
+fn main() { let z = (x as f64 / y as f64).floor() as usize; }
+
+
+fn main() { let z = (x   /* x */   as   /*y */     f64 / y   /* z */  as     /* a */    f64).floor()    /* b */ as /* c */ usize; }

tests/target/issue_4534.rs

@@ -0,0 +1,7 @@
+fn main() {
+    let z = (x as f64 / y as f64).floor() as usize;
+}
+
+fn main() {
+    let z = (x /* x */ as /*y */ f64 / y /* z */ as /* a */ f64).floor() /* b */ as /* c */ usize;
+}