Rename ConstStringValue -> FrozenStringValue

Summary:
There's `ConstFrozenStringN` type, which is `*FrozenValue` i. e. data, while `ConstFrozenString` is actually a `FrozenValue`, i. e. pointer.

`FrozenStringValue` name is more consistent. Also, the type has nothing to do with type being "const" (which means here statically allocated), it can store frozen heap allocated value.

Additionally, following diff D30884361 adds `StringValue` type. So the relation is:

* `FrozenStringValue` is a wrapper for `FrozenValue`
* `StringValue` is a wrapper for `Value`

Reviewed By: ndmitchell

Differential Revision: D30884360

fbshipit-source-id: 55493f25808ee47a090f52e3ab5062956f5d2c4a

Author: stepancheg

starlark/src/values/layout/constant.rs

@@ -53,8 +53,8 @@ impl<const N: usize> ConstFrozenStringN<N> {
     }
 
     /// Erase the type parameter, giving a slightly nicer user experience.
-    pub const fn erase(&'static self) -> ConstFrozenString {
-        ConstFrozenString(&self.repr)
+    pub const fn erase(&'static self) -> FrozenStringValue {
+        FrozenStringValue(&self.repr)
     }
 }
 
@@ -64,23 +64,23 @@ impl<const N: usize> ConstFrozenStringN<N> {
 ///
 /// ```
 /// use starlark::const_frozen_string;
-/// use starlark::values::{ConstFrozenString, FrozenValue};
+/// use starlark::values::{FrozenStringValue, FrozenValue};
 ///
-/// static RES: ConstFrozenString = const_frozen_string!("magic");
+/// static RES: FrozenStringValue = const_frozen_string!("magic");
 /// let fv: FrozenValue = RES.unpack();
 /// assert_eq!(Some("magic"), fv.to_value().unpack_str());
 /// ```
 #[derive(Copy, Clone, Dupe)]
-pub struct ConstFrozenString(&'static AValueRepr<StarlarkStr>);
+pub struct FrozenStringValue(&'static AValueRepr<StarlarkStr>);
 
-impl ConstFrozenString {
-    /// Obtain the [`FrozenValue`] for a [`ConstFrozenString`].
+impl FrozenStringValue {
+    /// Obtain the [`FrozenValue`] for a [`FrozenStringValue`].
     pub fn unpack(self) -> FrozenValue {
         FrozenValue::new_repr(self.0)
     }
 }
 
-/// Create a [`ConstFrozenString`].
+/// Create a [`FrozenStringValue`].
 #[macro_export]
 macro_rules! const_frozen_string {
     ($s:expr) => {{

starlark/src/values/layout/mod.rs

@@ -27,7 +27,7 @@ mod pointer_i32;
 mod value;
 mod value_captured;
 
-pub use constant::{ConstFrozenString, ConstFrozenStringN};
+pub use constant::{ConstFrozenStringN, FrozenStringValue};
 pub use heap::{Freezer, FrozenHeap, FrozenHeapRef, Heap, Tracer};
 pub(crate) use pointer_i32::PointerI32;
 pub use value::{FrozenValue, Value};