update annotation docs to reference signatures

Author: ginsbach

docs/codeql/ql-language-reference/annotations.rst

@@ -126,7 +126,7 @@ body must also be annotated with ``cached``, otherwise a compiler error is repor
 ``deprecated``
 ==============
 
-**Available for**: |classes|, |algebraic datatypes|, |member predicates|, |non-member predicates|, |imports|, |fields|, |modules|, |aliases|
+**Available for**: |classes|, |algebraic datatypes|, |member predicates|, |non-member predicates|, |imports|, |fields|, |modules|, |aliases|, |signatures|
 
 The ``deprecated`` annotation is applied to names that are outdated and scheduled for removal
 in a future release of QL.
@@ -235,7 +235,7 @@ warning.
 ``private``
 ===========
 
-**Available for**: |classes|, |algebraic datatypes|, |member predicates|, |non-member predicates|, |imports|, |fields|, |modules|, |aliases|
+**Available for**: |classes|, |algebraic datatypes|, |member predicates|, |non-member predicates|, |imports|, |fields|, |modules|, |aliases|, |signatures|
 
 The ``private`` annotation is used to prevent names from being exported.
 
@@ -461,7 +461,7 @@ For more information, see ":ref:`monotonic-aggregates`."
 Binding sets
 ============
 
-**Available for**: |classes|, |characteristic predicates|, |member predicates|, |non-member predicates|
+**Available for**: |classes|, |characteristic predicates|, |member predicates|, |non-member predicates|, |predicate signatures|, |type signatures|
 
 ``bindingset[...]``
 -------------------
@@ -491,3 +491,6 @@ The ``bindingset`` annotation takes a comma-separated list of variables.
 .. |type-aliases|              replace:: :ref:`type aliases <type-aliases>`
 .. |algebraic datatypes|       replace:: :ref:`algebraic datatypes <algebraic-datatypes>`
 .. |expressions|               replace:: :ref:`expressions <expressions>`
+.. |signatures|                replace:: :ref:`signatures <signatures>`
+.. |predicate signatures|      replace:: :ref:`predicate signatures <predicate-signatures>`
+.. |type signatures|           replace:: :ref:`type signatures <type-signatures>`

docs/codeql/ql-language-reference/signatures.rst

@@ -10,6 +10,10 @@ Signatures
 Parameterized modules use signatures as a type system for their parameters.
 There are three categories of signatures: **predicate signatures**, **type signatures**, and **module signatures**.
 
+.. index:: predicate signature
+
+.. _predicate-signatures:
+
 Predicate signatures
 ====================
 
@@ -36,6 +40,10 @@ For example:
 
     signature int operator(int lhs, int rhs);
 
+.. index:: type signature
+
+.. _type-signatures:
+
 Type signatures
 ===============
 
@@ -66,6 +74,10 @@ For example:
       string toString();
     }
 
+.. index:: module signature
+
+.. _module-signatures:
+
 Module signatures
 =================