Do not bound Arbitrary parameters passed to InputWeightPrediction

Now that InputWeightPrediction can no longer overflow due to extreme
values, there is no longer need to bound the Arbitrary parameters
passed.

Author: yancyribbens

bitcoin/src/blockdata/transaction.rs

@@ -1165,31 +1165,23 @@ mod sealed {
 #[cfg(feature = "arbitrary")]
 impl<'a> Arbitrary<'a> for InputWeightPrediction {
     fn arbitrary(u: &mut Unstructured<'a>) -> arbitrary::Result<Self> {
-        // limit script size to 4Mwu block size.
-        let max_block = Weight::MAX_BLOCK.to_wu() as usize;
-        let input_script_len = u.int_in_range(0..=max_block)?;
-        let remaining = max_block - input_script_len;
-
-        // create witness data if there is remaining space.
-        let mut witness_length = u.int_in_range(0..=remaining)?;
-        let mut witness_element_lengths = Vec::new();
-
-        // build vec of random witness element lengths.
-        while witness_length > 0 {
-            let elem = u.int_in_range(1..=witness_length)?;
-            witness_element_lengths.push(elem);
-            witness_length -= elem;
-        }
-
         match u.int_in_range(0..=7)? {
             0 => Ok(InputWeightPrediction::P2WPKH_MAX),
             1 => Ok(InputWeightPrediction::NESTED_P2WPKH_MAX),
             2 => Ok(InputWeightPrediction::P2PKH_COMPRESSED_MAX),
             3 => Ok(InputWeightPrediction::P2PKH_UNCOMPRESSED_MAX),
             4 => Ok(InputWeightPrediction::P2TR_KEY_DEFAULT_SIGHASH),
             5 => Ok(InputWeightPrediction::P2TR_KEY_NON_DEFAULT_SIGHASH),
-            6 => Ok(InputWeightPrediction::new(input_script_len, witness_element_lengths)),
-            _ => Ok(InputWeightPrediction::from_slice(input_script_len, &witness_element_lengths)),
+            6 => {
+                let input_script_len = usize::arbitrary(u)?;
+                let witness_element_lengths: Vec<usize> = Vec::arbitrary(u)?;
+                Ok(InputWeightPrediction::new(input_script_len, witness_element_lengths))
+            }
+            _ => {
+                let input_script_len = usize::arbitrary(u)?;
+                let witness_element_lengths: Vec<usize> = Vec::arbitrary(u)?;
+                Ok(InputWeightPrediction::from_slice(input_script_len, &witness_element_lengths))
+            }
         }
     }
 }