[gardening] Fix a vs. an issues

Author: practicalswift

include/swift/AST/DeclContext.h

@@ -285,13 +285,13 @@ class alignas(1 << DeclContextAlignInBits) DeclContext {
 
   /// Gets the type being declared by this context.
   ///
-  /// - Generic types return an bound generic type using archetypes.
+  /// - Generic types return a bound generic type using archetypes.
   /// - Non-type contexts return a null type.
   Type getDeclaredTypeInContext() const;
 
   /// Gets the type being declared by this context.
   ///
-  /// - Generic types return an bound generic type using interface types.
+  /// - Generic types return a bound generic type using interface types.
   /// - Non-type contexts return a null type.
   Type getDeclaredInterfaceType() const;
 

include/swift/AST/GenericEnvironment.h

@@ -59,7 +59,7 @@ class GenericEnvironment final {
   /// Map an interface type to a contextual type.
   Type mapTypeIntoContext(ModuleDecl *M, Type type) const;
 
-  /// Map an generic parameter type to a contextual type.
+  /// Map a generic parameter type to a contextual type.
   Type mapTypeIntoContext(GenericTypeParamType *type) const;
 
   /// Derive a contextual type substitution map from a substitution array.