Extract integer conversion into a function

compiler/rustc_lint/src/types/literal.rs

@@ -204,29 +204,35 @@ fn get_type_suggestion(t: Ty<'_>, val: u128, negative: bool) -> Option<&'static
     match t.kind() {
         ty::Uint(ty::UintTy::Usize) | ty::Int(ty::IntTy::Isize) => None,
         ty::Uint(_) => Some(Integer::fit_unsigned(val).uint_ty_str()),
-        ty::Int(_) if negative => {
-            if val > i128::MAX as u128 + 1 {
-                None
-            } else {
-                Some(Integer::fit_signed(val.wrapping_neg() as i128).int_ty_str())
-            }
-        }
         ty::Int(int) => {
-            let unsigned = Integer::fit_unsigned(val);
-            Some(if let Ok(signed) = i128::try_from(val).map(Integer::fit_signed) {
-                if Some(unsigned.size().bits()) == int.bit_width() {
-                    unsigned.uint_ty_str()
-                } else {
-                    signed.int_ty_str()
-                }
+            let signed = literal_to_i128(val, negative).map(|v| Integer::fit_signed(v));
+            if negative {
+                signed.map(Integer::int_ty_str)
             } else {
-                unsigned.uint_ty_str()
-            })
+                let unsigned = Integer::fit_unsigned(val);
+                Some(if let Some(signed) = signed {
+                    if Some(unsigned.size().bits()) == int.bit_width() {
+                        unsigned.uint_ty_str()
+                    } else {
+                        signed.int_ty_str()
+                    }
+                } else {
+                    unsigned.uint_ty_str()
+                })
+            }
         }
         _ => None,
     }
 }
 
+fn literal_to_i128(val: u128, negative: bool) -> Option<i128> {
+    if negative {
+        (val <= i128::MAX as u128 + 1).then(|| val.wrapping_neg() as i128)
+    } else {
+        val.try_into().ok()
+    }
+}
+
 fn lint_int_literal<'tcx>(
     cx: &LateContext<'tcx>,
     type_limits: &TypeLimits,