[spec] Fix context composition in text format (WebAssembly#1578)

document/core/text/modules.rst

@@ -108,7 +108,7 @@ If inline declarations are given, then their types must match the referenced :re
         \end{array} \\
    \end{array}
 
-The synthesized attribute of a |Ttypeuse| is a pair consisting of both the used :ref:`type index <syntax-typeidx>` and the updated :ref:`identifier context <text-context>` including possible parameter identifiers.
+The synthesized attribute of a |Ttypeuse| is a pair consisting of both the used :ref:`type index <syntax-typeidx>` and the local :ref:`identifier context <text-context>` containing possible parameter identifiers.
 The following auxiliary function extracts optional identifiers from parameters:
 
 .. math::
@@ -200,7 +200,7 @@ Function definitions can bind a symbolic :ref:`function identifier <text-id>`, a
      \text{(}~\text{func}~~\Tid^?~~x,I'{:}\Ttypeuse_I~~
      (t{:}\Tlocal)^\ast~~(\X{in}{:}\Tinstr_{I''})^\ast~\text{)} \\ &&& \qquad
        \Rightarrow\quad \{ \FTYPE~x, \FLOCALS~t^\ast, \FBODY~\X{in}^\ast~\END \} \\ &&& \qquad\qquad\qquad
-       (\iff I'' = I' \compose \{\ILOCALS~\F{id}(\Tlocal)^\ast\} \idcwellformed) \\[1ex]
+       (\iff I'' = I \compose I' \compose \{\ILOCALS~\F{id}(\Tlocal)^\ast\} \idcwellformed) \\[1ex]
    \production{local} & \Tlocal &::=&
      \text{(}~\text{local}~~\Tid^?~~t{:}\Tvaltype~\text{)}
        \quad\Rightarrow\quad t \\