generic_arguments.md: substs -> GenericArgs

See rust-lang/rust#113591

src/generic_arguments.md

@@ -1,36 +1,36 @@
 # Generic arguments
-A `ty::subst::GenericArg<'tcx>` represents some entity in the type system: a type
+A `ty::GenericArg<'tcx>` represents some entity in the type system: a type
 (`Ty<'tcx>`), lifetime (`ty::Region<'tcx>`) or constant (`ty::Const<'tcx>`).
-`GenericArg` is used to perform substitutions of generic parameters for concrete
+`GenericArg` is used to perform instantiation of generic parameters to concrete
 arguments, such as when calling a function with generic parameters explicitly
-with type arguments. Substitutions are represented using the
-[`Subst` type](#subst) as described below.
+with type arguments. Instantiations are represented using the
+[`GenericArgs` type](#genericargs) as described below.
 
-## `Subst`
-`ty::subst::Subst<'tcx>` is intuitively simply a slice of `GenericArg<'tcx>`s,
-acting as an ordered list of substitutions from generic parameters to
+## `GenericArgs`
+`ty::GenericArgs<'tcx>` is intuitively simply a slice of `GenericArg<'tcx>`s,
+acting as an ordered list of generic parameters instantiated to
 concrete arguments (such as types, lifetimes and consts).
 
 For example, given a `HashMap<K, V>` with two type parameters, `K` and `V`, an
 instantiation of the parameters, for example `HashMap<i32, u32>`, would be
-represented by the substitution `&'tcx [tcx.types.i32, tcx.types.u32]`.
+represented by `&'tcx [tcx.types.i32, tcx.types.u32]`.
 
-`Subst` provides various convenience methods to instantiate substitutions
+`GenericArgs` provides various convenience methods to instantiate generic arguments
 given item definitions, which should generally be used rather than explicitly
-constructing such substitution slices.
+instantiating such slices.
 
 ## `GenericArg`
 The actual `GenericArg` struct is optimised for space, storing the type, lifetime or
 const as an interned pointer containing a tag identifying its kind (in the
-lowest 2 bits). Unless you are working with the `Subst` implementation
+lowest 2 bits). Unless you are working with the `GenericArgs` implementation
 specifically, you should generally not have to deal with `GenericArg` and instead
 make use of the safe [`GenericArgKind`](#genericargkind) abstraction.
 
 ## `GenericArgKind`
 As `GenericArg` itself is not type-safe, the `GenericArgKind` enum provides a more
 convenient and safe interface for dealing with generic arguments. An
 `GenericArgKind` can be converted to a raw `GenericArg` using `GenericArg::from()`
-(or simply `.into()` when the context is clear). As mentioned earlier, substitution
+(or simply `.into()` when the context is clear). As mentioned earlier, instantiation
 lists store raw `GenericArg`s, so before dealing with them, it is preferable to
 convert them to `GenericArgKind`s first. This is done by calling the `.unpack()`
 method.
@@ -44,7 +44,7 @@ fn deal_with_generic_arg<'tcx>(generic_arg: GenericArg<'tcx>) -> GenericArg<'tcx
         GenericArgKind::Lifetime(lt) => { /* ... */ }
         GenericArgKind::Const(ct) => { /* ... */ }
     };
-    // Pack the `GenericArgKind` to store it in a substitution list.
+    // Pack the `GenericArgKind` to store it in a generic args list.
     new_generic_arg.into()
 }
 ```