From 2bc59c7ae2631863e947ccdba42b989feeec6b36 Mon Sep 17 00:00:00 2001
From: b-naber <bn263@gmx.de>
Date: Tue, 12 Apr 2022 13:08:47 +0200
Subject: [PATCH] add some helper methods to ScalarInt

---
 compiler/rustc_middle/src/ty/consts/int.rs | 92 ++++++++++++++++++++++
 1 file changed, 92 insertions(+)

diff --git a/compiler/rustc_middle/src/ty/consts/int.rs b/compiler/rustc_middle/src/ty/consts/int.rs
index 72623ba54ee..a3ce674c115 100644
--- a/compiler/rustc_middle/src/ty/consts/int.rs
+++ b/compiler/rustc_middle/src/ty/consts/int.rs
@@ -237,6 +237,98 @@ impl ScalarInt {
     pub fn try_to_machine_usize<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Result<u64, Size> {
         Ok(self.to_bits(tcx.data_layout.pointer_size)? as u64)
     }
+
+    /// Tries to convert the `ScalarInt` to an unsigned integer of the given size.
+    /// Fails if the size of the `ScalarInt` is unequal to `size` and returns the
+    /// `ScalarInt`s size in that case.
+    #[inline]
+    pub fn try_to_uint(self, size: Size) -> Result<u128, Size> {
+        self.to_bits(size)
+    }
+
+    // Tries to convert the `ScalarInt` to `u8`. Fails if the `size` of the `ScalarInt`
+    // in not equal to `Size { raw: 1 }` and returns the `size` value of the `ScalarInt` in
+    // that case.
+    #[inline]
+    pub fn try_to_u8(self) -> Result<u8, Size> {
+        self.to_bits(Size::from_bits(8)).map(|v| u8::try_from(v).unwrap())
+    }
+
+    /// Tries to convert the `ScalarInt` to `u16`. Fails if the size of the `ScalarInt`
+    /// in not equal to `Size { raw: 2 }` and returns the `size` value of the `ScalarInt` in
+    /// that case.
+    #[inline]
+    pub fn try_to_u16(self) -> Result<u16, Size> {
+        self.to_bits(Size::from_bits(16)).map(|v| u16::try_from(v).unwrap())
+    }
+
+    /// Tries to convert the `ScalarInt` to `u32`. Fails if the `size` of the `ScalarInt`
+    /// in not equal to `Size { raw: 4 }` and returns the `size` value of the `ScalarInt` in
+    /// that case.
+    #[inline]
+    pub fn try_to_u32(self) -> Result<u32, Size> {
+        self.to_bits(Size::from_bits(32)).map(|v| u32::try_from(v).unwrap())
+    }
+
+    /// Tries to convert the `ScalarInt` to `u64`. Fails if the `size` of the `ScalarInt`
+    /// in not equal to `Size { raw: 8 }` and returns the `size` value of the `ScalarInt` in
+    /// that case.
+    #[inline]
+    pub fn try_to_u64(self) -> Result<u64, Size> {
+        self.to_bits(Size::from_bits(64)).map(|v| u64::try_from(v).unwrap())
+    }
+
+    /// Tries to convert the `ScalarInt` to `u128`. Fails if the `size` of the `ScalarInt`
+    /// in not equal to `Size { raw: 16 }` and returns the `size` value of the `ScalarInt` in
+    /// that case.
+    #[inline]
+    pub fn try_to_u128(self) -> Result<u128, Size> {
+        self.to_bits(Size::from_bits(128))
+    }
+
+    /// Tries to convert the `ScalarInt` to a signed integer of the given size.
+    /// Fails if the size of the `ScalarInt` is unequal to `size` and returns the
+    /// `ScalarInt`s size in that case.
+    #[inline]
+    pub fn try_to_int(self, size: Size) -> Result<i128, Size> {
+        let b = self.to_bits(size)?;
+        Ok(size.sign_extend(b) as i128)
+    }
+
+    /// Tries to convert the `ScalarInt` to i8.
+    /// Fails if the size of the `ScalarInt` is unequal to `Size { raw: 1 }`
+    /// and returns the `ScalarInt`s size in that case.
+    pub fn try_to_i8(self) -> Result<i8, Size> {
+        self.try_to_int(Size::from_bits(8)).map(|v| i8::try_from(v).unwrap())
+    }
+
+    /// Tries to convert the `ScalarInt` to i16.
+    /// Fails if the size of the `ScalarInt` is unequal to `Size { raw: 2 }`
+    /// and returns the `ScalarInt`s size in that case.
+    pub fn try_to_i16(self) -> Result<i16, Size> {
+        self.try_to_int(Size::from_bits(16)).map(|v| i16::try_from(v).unwrap())
+    }
+
+    /// Tries to convert the `ScalarInt` to i32.
+    /// Fails if the size of the `ScalarInt` is unequal to `Size { raw: 4 }`
+    /// and returns the `ScalarInt`s size in that case.
+    pub fn try_to_i32(self) -> Result<i32, Size> {
+        self.try_to_int(Size::from_bits(32)).map(|v| i32::try_from(v).unwrap())
+    }
+
+    /// Tries to convert the `ScalarInt` to i64.
+    /// Fails if the size of the `ScalarInt` is unequal to `Size { raw: 8 }`
+    /// and returns the `ScalarInt`s size in that case.
+    pub fn try_to_i64(self) -> Result<i64, Size> {
+        self.try_to_int(Size::from_bits(64)).map(|v| i64::try_from(v).unwrap())
+    }
+
+    /// Tries to convert the `ScalarInt` to i128.
+    /// Fails if the size of the `ScalarInt` is unequal to `Size { raw: 16 }`
+    /// and returns the `ScalarInt`s size in that case.
+    pub fn try_to_i128(self) -> Result<i128, Size> {
+        self.try_to_int(Size::from_bits(128)).map(|v| i128::try_from(v).unwrap())
+    }
 }
 
 macro_rules! from {