Add uninitialized intrinsic (#522)

This effectively just results in a null pointer, but it's cast to be
whatever generic value `T` it's required to be. This can be dangerous of
course and requires additional checks, but is useful in cases where
performance is important (like with `MapEntry<K, V>[]` in the `Map`
type); this approach can be leveraged instead of using `Option<T>`.
It's much less ergonomic and type-safe, but it doesn't result in an
extra layer of allocation and pointer-indirection.

projects/compiler/src/compiler.abra

@@ -2531,6 +2531,8 @@ export type Compiler {
           curVal = try self._compileFunctionValue(label.position, fn, targetParamTypes, capturesMem, selfVal)
         }
         AccessorPathSegment.Field(label, ty, field, isOptSafe) => {
+          val selfInstType = try self._addResolvedGenericsLayerForInstanceMethod(instType, field.name.name, label.position)
+
           var optSafeCtx: (Label, Value, QbeFunction, Label)? = None
 
           if isOptSafe {
@@ -2614,6 +2616,8 @@ export type Compiler {
           val (_instTy, typeArgs) = try self._getInstanceTypeForType(ty)
           instTy = _instTy
           instType = Type(kind: TypeKind.Instance(instTy, typeArgs))
+
+          self._resolvedGenerics.popLayer()
         }
       }
     }
@@ -3063,6 +3067,19 @@ export type Compiler {
 
         Ok(argVal)
       }
+      "uninitialized" => {
+        self._currentFn.block.addComment("begin uninitialized...")
+
+        val innerTy = if self._resolvedGenerics.resolveGeneric("T") |ty| ty else unreachable("(uninitialized) could not resolve T for uninitialized<T>()")
+        val innerTySize = try self._pointerSize(innerTy)
+        if innerTySize != QbeType.U64.size() unreachable("innerTySize != QbeType.U64.size()")
+
+        val res = Value.Int(0)
+
+        self._currentFn.block.addComment("...uninitialized end")
+
+        Ok(res)
+      }
       "u64_to_string" => {
         self._currentFn.block.addComment("begin u64_to_string...")
         val _arg = if arguments[0] |arg| arg else unreachable("'u64_to_string' has 1 required argument")

projects/std/src/_intrinsics.abra

@@ -16,6 +16,9 @@ export func moduleNames(): Pointer<Byte>
 @Intrinsic("functionnames")
 export func functionNames(): Pointer<Byte>
 
+@Intrinsic("uninitialized")
+export func uninitialized<T>(): T
+
 @Intrinsic("u64_to_string")
 export func u64ToString(i: Int): String