Add a helper method with an explicit name instead of hand rolling a match 3x

Author: oli-obk

compiler/rustc_codegen_ssa/src/mir/rvalue.rs

@@ -286,7 +286,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
 
                         let newval = match (r_t_in, r_t_out) {
                             (CastTy::Int(i), CastTy::Int(_)) => {
-                                bx.intcast(llval, ll_t_out, matches!(i, IntTy::I))
+                                bx.intcast(llval, ll_t_out, i.is_signed())
                             }
                             (CastTy::Float, CastTy::Float) => {
                                 let srcsz = bx.cx().float_width(ll_t_in);
@@ -300,7 +300,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                                 }
                             }
                             (CastTy::Int(i), CastTy::Float) => {
-                                if matches!(i, IntTy::I) {
+                                if i.is_signed() {
                                     bx.sitofp(llval, ll_t_out)
                                 } else {
                                     bx.uitofp(llval, ll_t_out)
@@ -311,7 +311,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                             }
                             (CastTy::Int(i), CastTy::Ptr(_)) => {
                                 let usize_llval =
-                                    bx.intcast(llval, bx.cx().type_isize(), matches!(i, IntTy::I));
+                                    bx.intcast(llval, bx.cx().type_isize(), i.is_signed());
                                 bx.inttoptr(usize_llval, ll_t_out)
                             }
                             (CastTy::Float, CastTy::Int(IntTy::I)) => {

compiler/rustc_middle/src/ty/cast.rs

@@ -15,6 +15,12 @@ pub enum IntTy {
     Char,
 }
 
+impl IntTy {
+    pub fn is_signed(self) -> bool {
+        matches!(self, Self::I)
+    }
+}
+
 // Valid types for the result of a non-coercion cast
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
 pub enum CastTy<'tcx> {