Unify vocabulary related to the feature.

libsolidity/analysis/TypeChecker.cpp

@@ -3872,7 +3872,7 @@ void TypeChecker::endVisit(UsingForDirective const& _usingFor)
 		m_errorReporter.typeError(
 			9921_error,
 			_usingFor.location(),
-			"The \"using\" directive cannot be used to attach functions to enum types."
+			"The \"using\" directive cannot be used to bind functions to enum types."
 		);
 
 	Type const* normalizedType = TypeProvider::withLocationIfReference(

libsolidity/ast/AST.h

@@ -645,11 +645,11 @@ private:
 /**
  * Using for directive:
  *
- * 1. `using LibraryName for T` attaches all functions from the library `LibraryName` to the type `T`
+ * 1. `using LibraryName for T` binds all functions from the library `LibraryName` to the type `T`
- * 2. `using LibraryName for *` attaches to all types.
+ * 2. `using LibraryName for *` binds to all types.
- * 3. `using {f1, f2, ..., fn} for T` attaches the functions `f1`, `f2`, ...,
+ * 3. `using {f1, f2, ..., fn} for T` binds the functions `f1`, `f2`, ...,
  *     `fn`, respectively to `T`.
- * 4. `using {f1 as op1, f2 as op2, ..., fn as opn} for T` bounds operator `opn` to function `fn` for type `T`.
+ * 4. `using {f1 as op1, f2 as op2, ..., fn as opn} for T` binds function `fn` to operator `opn` for type `T`.
  *
  * For version 3, T has to be implicitly convertible to the first parameter type of
  * all functions, and this is checked at the point of the using statement. For versions 1 and

test/libsolidity/syntaxTests/operators/custom/operator_bound_to_enum.sol

@@ -10,4 +10,4 @@ function add(E, E) pure returns (E) {
 }
 
 // ----
-// TypeError 9921: (0-23): The "using" directive cannot be used to attach functions to enum types.
+// TypeError 9921: (0-23): The "using" directive cannot be used to bind functions to enum types.