lib/*: fix docs to use "returns" instead of "return" (#442388)

lib/attrsets.nix

···
     ;
 
   /**
-    Return an attribute from nested attribute sets.
+    Returns an attribute from nested attribute sets.
 
     Nix has an [attribute selection operator `.`](https://nixos.org/manual/nix/stable/language/operators#attribute-selection) which is sufficient for such queries, as long as the number of attributes is static. For example:
 
···
     attrByPath' 0 set;
 
   /**
-    Return if an attribute from nested attribute set exists.
+    Returns if an attribute from nested attribute set exists.
 
     Nix has a [has attribute operator `?`](https://nixos.org/manual/nix/stable/language/operators#has-attribute), which is sufficient for such queries, as long as the number of attributes is static. For example:
 
···
     hasAttrByPath' 0 e;
 
   /**
-    Return the longest prefix of an attribute path that refers to an existing attribute in a nesting of attribute sets.
+    Returns the longest prefix of an attribute path that refers to an existing attribute in a nesting of attribute sets.
 
     Can be used after [`mapAttrsRecursiveCond`](#function-library-lib.attrsets.mapAttrsRecursiveCond) to apply a condition,
     although this will evaluate the predicate function on sibling attributes as well.
···
     updates: value: go 0 true value updates;
 
   /**
-    Return the specified attributes from a set.
+    Returns the specified attributes from a set.
 
     # Inputs
 
···
   attrVals = nameList: set: map (x: set.${x}) nameList;
 
   /**
-    Return the values of all attributes in the given set, sorted by
+    Returns the values of all attributes in the given set, sorted by
     attribute name.
 
     # Type

lib/deprecated/misc.nix

···
     name: default: attrs:
     attrs.${name} or default;
 
-  # Return the second argument if the first one is true or the empty version
+  # Returns the second argument if the first one is true or the empty version
   # of the second argument.
   ifEnable =
     cond: val:
···
     else
       null;
 
-  # Return true only if there is an attribute and it is true.
+  # Returns true only if there is an attribute and it is true.
   checkFlag =
     attrSet: name:
     if name == "true" then

lib/fixed-points.nix

···
     x;
 
   /**
-    Return the fixpoint that `f` converges to when called iteratively, starting
+    Returns the fixpoint that `f` converges to when called iteratively, starting
     with the input `x`.
 
     ```

lib/lists.nix

···
     if index == null then default else elemAt list index;
 
   /**
-    Return true if function `pred` returns true for at least one
+    Returns true if function `pred` returns true for at least one
     element of `list`.
 
     # Inputs
···
   any = builtins.any;
 
   /**
-    Return true if function `pred` returns true for all elements of
+    Returns true if function `pred` returns true for all elements of
     `list`.
 
     # Inputs
···
   optional = cond: elem: if cond then [ elem ] else [ ];
 
   /**
-    Return a list or an empty list, depending on a boolean value.
+    Returns a list or an empty list, depending on a boolean value.
 
     # Inputs
 
···
   toList = x: if isList x then x else [ x ];
 
   /**
-    Return a list of integers from `first` up to and including `last`.
+    Returns a list of integers from `first` up to and including `last`.
 
     # Inputs
 
···
   range = first: last: if first > last then [ ] else genList (n: first + n) (last - first + 1);
 
   /**
-    Return a list with `n` copies of an element.
+    Returns a list with `n` copies of an element.
 
     # Inputs
 
···
     map (x: elemAt x 1) (sort less prepared);
 
   /**
-    Return the first (at most) N elements of a list.
+    Returns the first (at most) N elements of a list.
 
     # Inputs
 
···
   take = count: sublist 0 count;
 
   /**
-    Return the last (at most) N elements of a list.
+    Returns the last (at most) N elements of a list.
 
     # Inputs
 
···
       throw "lib.lists.removePrefix: First argument is not a list prefix of the second argument";
 
   /**
-    Return a list consisting of at most `count` elements of `list`,
+    Returns a list consisting of at most `count` elements of `list`,
     starting at index `start`.
 
     # Inputs
···
     take commonPrefixLength list1;
 
   /**
-    Return the last element of a list.
+    Returns the last element of a list.
 
     This function throws an error if the list is empty.
 
···
     elemAt list (length list - 1);
 
   /**
-    Return all elements but the last.
+    Returns all elements but the last.
 
     This function throws an error if the list is empty.
 
···
     take (length list - 1) list;
 
   /**
-    Return the image of the cross product of some lists by a function.
+    Returns the image of the cross product of some lists by a function.
 
     # Examples
     :::{.example}

lib/modules.nix

···
   };
 
   /**
-    Return a definition with file location information.
+    Returns a definition with file location information.
   */
   mkDefinition = args@{ file, value, ... }: args // { _type = "definition"; };
 
···
     };
 
   /**
-    Return a module that causes a warning to be shown if the
+    Returns a module that causes a warning to be shown if the
     specified option is defined. For example,
 
       mkRemovedOptionModule [ "boot" "loader" "grub" "bootDevice" ] "<replacement instructions>"
···
     };
 
   /**
-    Return a module that causes a warning to be shown if the
+    Returns a module that causes a warning to be shown if the
     specified "from" option is defined; the defined value is however
     forwarded to the "to" option. This can be used to rename options
     while providing backward compatibility. For example,
···
     };
 
   /**
-    Return a module that causes a warning to be shown if any of the "from"
+    Returns a module that causes a warning to be shown if any of the "from"
     option is defined; the defined values can be used in the "mergeFn" to set
     the "to" value.
     This function can be used to merge multiple options into one that has a
···
 
   /**
     Single "from" version of mkMergedOptionModule.
-    Return a module that causes a warning to be shown if the "from" option is
+    Returns a module that causes a warning to be shown if the "from" option is
     defined; the defined value can be used in the "mergeFn" to set the "to"
     value.
     This function can be used to change an option into another that has a
···
   mkDerivedConfig = opt: f: mkOverride (opt.highestPrio or defaultOverridePriority) (f opt.value);
 
   /**
-    Return a module that help declares an option that has been renamed.
+    Returns a module that help declares an option that has been renamed.
     When a value is defined for the old option, it is forwarded to the `to` option.
   */
   doRename =

lib/options.nix

···
     loc: defs:
     if defs == [ ] then
       abort "This case should never happen."
-    # Return early if we only have one element
+    # Returns early if we only have one element
     # This also makes it work for functions, because the foldl' below would try
     # to compare the first element with itself, which is false for functions
     else if length defs == 1 then

lib/path/default.nix

···
     isValid
     ;
 
-  # Return the reason why a subpath is invalid, or `null` if it's valid
+  # Returns the reason why a subpath is invalid, or `null` if it's valid
   subpathInvalidReason =
     value:
     if !isString value then

lib/strings.nix

···
     if len == 0 then [ (addContextFrom str "") ] else map (addContextFrom str) (go 0 "" [ ]);
 
   /**
-    Return a string without the specified prefix, if the prefix matches.
+    Returns a string without the specified prefix, if the prefix matches.
 
     # Inputs
 
···
       );
 
   /**
-    Return a string without the specified suffix, if the suffix matches.
+    Returns a string without the specified suffix, if the suffix matches.
 
     # Inputs
 
···
       );
 
   /**
-    Return true if string `v1` denotes a version older than `v2`.
+    Returns true if string `v1` denotes a version older than `v2`.
 
     # Inputs
 
···
   versionOlder = v1: v2: compareVersions v2 v1 == 1;
 
   /**
-    Return true if string v1 denotes a version equal to or newer than v2.
+    Returns true if string v1 denotes a version equal to or newer than v2.
 
     # Inputs
 

lib/trivial.nix

···
     f b a;
 
   /**
-    Return `maybeValue` if not null, otherwise return `default`.
+    Returns `maybeValue` if not null, otherwise return `default`.
 
     # Inputs
 
···
   ## Integer operations
 
   /**
-    Return minimum of two numbers.
+    Returns minimum of two numbers.
 
     # Inputs
 
···
   min = x: y: if x < y then x else y;
 
   /**
-    Return maximum of two numbers.
+    Returns maximum of two numbers.
 
     # Inputs
 

lib/types.nix

···
     # `optionType`: The option type to parenthesize or not.
     #   The option whose description we're returning.
     #
-    # Return value
+    # Returns value
     #
     # The description of the `optionType`, with parentheses if there may be an
     # ambiguity.