UnpackValue for more integer types

Summary: Used in the following diff D38712859.

Reviewed By: bobyangyf

Differential Revision: D38712854

fbshipit-source-id: 5e6269cb9979a6642bf91526d4495f649aaf4fd4

Author: stepancheg

starlark/src/values/layout/value.rs

@@ -309,6 +309,18 @@ impl<'v> Value<'v> {
         }
     }
 
+    pub(crate) fn unpack_integer<I>(self) -> Option<I>
+    where
+        I: TryFrom<i32>,
+        I: TryFrom<&'v BigInt>,
+    {
+        match self.unpack_num()? {
+            Num::Float(_) => None,
+            Num::Int(x) => I::try_from(x).ok(),
+            Num::BigInt(x) => x.unpack_integer(),
+        }
+    }
+
     /// Obtain the underlying `bool` if it is a boolean.
     pub fn unpack_bool(self) -> Option<bool> {
         let p = self.0.raw().ptr_value();

starlark/src/values/types/bigint/convert.rs

@@ -22,6 +22,7 @@ use crate::values::AllocValue;
 use crate::values::FrozenHeap;
 use crate::values::FrozenValue;
 use crate::values::Heap;
+use crate::values::UnpackValue;
 use crate::values::Value;
 
 impl StarlarkTypeRepr for u32 {
@@ -143,3 +144,33 @@ impl AllocFrozenValue for isize {
         }
     }
 }
+
+impl<'v> UnpackValue<'v> for u32 {
+    fn unpack_value(value: Value<'v>) -> Option<u32> {
+        value.unpack_integer()
+    }
+}
+
+impl<'v> UnpackValue<'v> for u64 {
+    fn unpack_value(value: Value<'v>) -> Option<u64> {
+        value.unpack_integer()
+    }
+}
+
+impl<'v> UnpackValue<'v> for i64 {
+    fn unpack_value(value: Value<'v>) -> Option<i64> {
+        value.unpack_integer()
+    }
+}
+
+impl<'v> UnpackValue<'v> for usize {
+    fn unpack_value(value: Value<'v>) -> Option<usize> {
+        value.unpack_integer()
+    }
+}
+
+impl<'v> UnpackValue<'v> for isize {
+    fn unpack_value(value: Value<'v>) -> Option<isize> {
+        value.unpack_integer()
+    }
+}

starlark/src/values/types/bigint/mod.rs

@@ -160,6 +160,10 @@ impl StarlarkBigInt {
             ))
         }
     }
+
+    pub(crate) fn unpack_integer<'v, I: TryFrom<&'v BigInt>>(&'v self) -> Option<I> {
+        I::try_from(&self.value).ok()
+    }
 }
 
 impl PartialEq<i32> for StarlarkBigInt {