fix typo

Co-Authored-By: Jane Lusby <[email protected]>

Author: anp

src/codegen/implicit-caller-location.md

@@ -52,28 +52,28 @@ explained in terms of how it works in a `const` context.
 ## Caller Location in `const`
 
 There are two main phases to returning the caller location in a const context: walking up the stack
-to find it and allocating a const value to return.
+to find the right location and allocating a const value to return.
+
+### Finding the right `Location`
 
 In a const context we "walk up the stack" from where the intrinsic is invoked, stopping when we 
 reach the first function call in the stack which does *not* have the attribute. This walk is in
-[`InterpCx::find_closest_untracked_caller_location()`][const-find-closest] which returns 
-`Option<Span>`.
-
-If the caller of the current function is untracked, it returns `None`. We use the span for the
-intrinsic's callsite in this case.
+[`InterpCx::find_closest_untracked_caller_location()`][const-find-closest].
 
-Otherwise it searches by iterating in reverse over [`Frame`][const-frame]s in the [InterpCx::stack],
+Starting at the bottom, we iterate up over stack [`Frame`][const-frame]s in the [InterpCx::stack],
 calling [`InstanceDef::requires_caller_location`][requires-location] on the 
-[`Frame::instance`][frame-instance]'s def until it finds a `false` return. It then returns the span 
-of the prior still-tracked frame which is the "topmost" tracked function.
+[`Instance`s from each `Frame`][frame-instance]. We stop once we find one that returns `false` and
+return the span of the *previous* frame which was the "topmost" tracked function.
+
+### Allocating a static `Location`
 
-We use the same code in both contexts to allocate a static value for each `Location`. This is
-performed by the [`TyCtxt::const_caller_location()`][const-location-query] query. Internally this
-calls [`InterpCx::alloc_caller_location()`][alloc-location] and results in a unique 
+Once we have a `Span` we need to allocate static memory for the `Location`, which is performed by 
+the [`TyCtxt::const_caller_location()`][const-location-query] query. Internally this calls 
+[`InterpCx::alloc_caller_location()`][alloc-location] and results in a unique
 [memory kind][location-memory-kind]. The SSA codegen backend is able to emit code for these same 
-values.
+values, and we use this code there as well..
 
-Once our location has been allocated in static memory we return a pointer to it.
+Once our `Location` has been allocated in static memory, our intrinsic returns a reference to it.
 
 ## Generating code for `#[track_caller]` callees
 
@@ -157,8 +157,8 @@ probably the best we can do without modifying fully-stabilized type signatures.
 
 The `#[track_caller]` attribute is checked alongside other codegen attrs to ensure the function:
 
-* is not a foreign import (e.g. in an `extern {...}` block)
 * has `"Rust"` ABI (as opposed to `"C"`, etc...)
+* is not a foreign import (e.g. in an `extern {...}` block)
 * is not a closure
 * is not `#[naked]`
 
@@ -168,13 +168,13 @@ used in both const and codegen contexts to ensure correct propagation.
 
 ### Traits
 
-When applied to a trait method prototype, the attribute takes effect on all implementations of the
-trait method. When applied to a default trait method implementation, the attribute takes effect on
-that implementation *and* any overrides. It is valid to apply the attribute to a regular
-implementation of a trait method, regardless of whether the defining trait does. It is a no-op to
-apply the attribute to trait methods with the attribute in the trait definition, but a valid one.
+When applied to trait method implementations, the attribute works as it does for regular functions.
+
+When applied to a trait method prototype, the attribute applies to all implementations of the 
+method. When applied to a default trait method implementation, the attribute takes effect on
+that implementation *and* any overrides.
 
-Example:
+Examples:
 
 ```rust
 #![feature(track_caller)]