Rust: Apply fixes from code review

rust/ql/lib/codeql/rust/internal/Type.qll

@@ -352,16 +352,12 @@ class PtrMutType extends PtrType {
   PtrMutType() { this.getStruct() instanceof Builtins::PtrMutType }
 
   override string toString() { result = "*mut" }
-
-  override Location getLocation() { result instanceof EmptyLocation }
 }
 
 class PtrConstType extends PtrType {
   PtrConstType() { this.getStruct() instanceof Builtins::PtrConstType }
 
   override string toString() { result = "*const" }
-
-  override Location getLocation() { result instanceof EmptyLocation }
 }
 
 /**

rust/ql/test/library-tests/type-inference/raw_pointer.rs

@@ -28,11 +28,11 @@ fn raw_mut_borrow() {
 
 fn raw_mut_write(cond: bool) {
     let a = 10i32;
-    // The type of `x` must be inferred from the write below.
+    // The type of `ptr_written` must be inferred from the write below.
     let ptr_written = null_mut(); // $ target=null_mut type=ptr_written:TPtrMut.i32
     if cond {
         unsafe {
-            // NOTE: This write is undefined behavior because `x` is a null pointer.
+            // NOTE: This write is undefined behavior because `ptr_written` is a null pointer.
             *ptr_written = a;
             let _y = *ptr_written; // $ type=_y:i32
         }
@@ -40,11 +40,11 @@ fn raw_mut_write(cond: bool) {
 }
 
 fn raw_type_from_deref(cond: bool) {
-    // The type of `x` must be inferred from the read below.
+    // The type of `ptr_read` must be inferred from the read below.
     let ptr_read = null_mut(); // $ target=null_mut type=ptr_read:TPtrMut.i64
     if cond {
         unsafe {
-            // NOTE: This read is undefined behavior because `x` is a null pointer.
+            // NOTE: This read is undefined behavior because `ptr_read` is a null pointer.
             let _y: i64 = *ptr_read;
         }
     }