Implement indexing for arrays

examples/example.rs

@@ -142,3 +142,7 @@ unsafe fn call_uninit() -> u8 {
 /*unsafe fn deref_str_ptr(s: *const str) -> &'static str {
     &*s
 }*/
+
+fn use_array(arr: [u8; 3]) -> u8 {
+    arr[1]
+}

examples/mini_core.rs

@@ -141,3 +141,17 @@ pub mod intrinsics {
         pub fn uninit<T>() -> T;
     }
 }
+
+#[lang = "index"]
+pub trait Index<Idx: ?Sized> {
+    type Output: ?Sized;
+    fn index(&self, index: Idx) -> &Self::Output;
+}
+
+impl<T> Index<usize> for [T; 3] {
+    type Output = T;
+
+    fn index(&self, index: usize) -> &Self::Output {
+        &self[index]
+    }
+}

src/base.rs

@@ -800,7 +800,8 @@ pub fn trans_place<'a, 'tcx: 'a>(
                 ),
                 ProjectionElem::Field(field, _ty) => base.place_field(fx, field),
                 ProjectionElem::Index(local) => {
-                    unimplemented!("projection index {:?} {:?}", projection.base, local)
+                    let index = fx.get_local_place(local).to_cvalue(fx).load_value(fx);
+                    base.place_index(fx, index)
                 }
                 ProjectionElem::ConstantIndex {
                     offset,

src/common.rs

@@ -297,6 +297,21 @@ impl<'a, 'tcx: 'a> CPlace<'tcx> {
         CPlace::Addr(field_ptr, field_layout)
     }
 
+    pub fn place_index(self, fx: &mut FunctionCx<'a, 'tcx>, index: Value) -> CPlace<'tcx> {
+        let addr = self.expect_addr();
+        let layout = self.layout();
+        match layout.ty.sty {
+            TypeVariants::TyArray(elem_ty, _) => {
+                let elem_layout = fx.layout_of(elem_ty);
+                let size = fx.bcx.ins().iconst(types::I64, elem_layout.size.bytes() as i64);
+                let offset = fx.bcx.ins().imul(size, index);
+                CPlace::Addr(fx.bcx.ins().iadd(addr, offset), elem_layout)
+            }
+            TypeVariants::TySlice(_elem_ty) => unimplemented!("place_index(TySlice)"),
+            _ => bug!("place_index({:?})", layout.ty),
+        }
+    }
+
     pub fn unchecked_cast_to(self, layout: TyLayout<'tcx>) -> Self {
         match self {
             CPlace::Var(var, _) => CPlace::Var(var, layout),