From e64a254a4107d4f476abfceb963a88150de6c152 Mon Sep 17 00:00:00 2001
From: Chris B <cbieneman@microsoft.com>
Date: Wed, 13 Dec 2023 16:50:50 -0600
Subject: [PATCH] [Expr] Add Expr.Post.Subscript (#139)

This adds definitions for HLSL array subscripting. HLSL deviates from
C/C++ in part because of the lack of pointers.
---
 specs/language/expressions.tex  | 27 +++++++++++++++++++++++++++
 specs/language/placeholders.tex |  1 +
 2 files changed, 28 insertions(+)

diff --git a/specs/language/expressions.tex b/specs/language/expressions.tex
index b1308214..c388d6fb 100644
--- a/specs/language/expressions.tex
+++ b/specs/language/expressions.tex
@@ -133,3 +133,30 @@
   nested-name-specifier \opt{\keyword{template}} simple-template-id \terminal{::}
 \end{grammar}
 
+\Sec{Postfix Expressions}{Expr.Post}
+
+\begin{grammar}
+  \define{postfix-expression}\br
+  primary-expression\br
+  postfix-expression \terminal{[} expression \terminal{]}\br
+  postfix-expression \terminal{[} braced-init-list \terminal{]}\br
+  postfix-expression \terminal{(} \opt{expression-list} \terminal{)}\br
+  simple-type-specifier \terminal{(} \opt{expression-list} \terminal{)}\br
+  typename-specifier \terminal{(} \opt{expression} \terminal{)}\br
+  simple-type-specifier braced-init-list\br
+  typename-specifier braced-init-list\br
+  postfix-expression \terminal{.} \opt{\terminal{template}} id-expression\br
+  postfix-expression \terminal{->} \opt{\terminal{template}} id-expression\br
+  postfix-expression \terminal{++}\br
+  postfix-expression \terminal{--}
+\end{grammar}
+
+\Sec{Subscript}{Expr.Post.Subscript}
+
+\p A \textit{postfix-expression} followed by an expression in square brackets
+(\texttt{[ ]}) is a subscript expression. In an array subscript expression of
+the form \texttt{E1[E2]}, \texttt{E1} must either be a variable of array of
+\texttt{T[]}, or an object of type \texttt{T} where \texttt{T} provides an
+overloaded implementation of \texttt{operator[]} (\ref{Overload}).\footnote{HLSL
+does not support the base address of a subscript operator being the expression
+inside the braces, which is valid in C and C++.}
diff --git a/specs/language/placeholders.tex b/specs/language/placeholders.tex
index b51bca4b..be3ecd52 100644
--- a/specs/language/placeholders.tex
+++ b/specs/language/placeholders.tex
@@ -1,4 +1,5 @@
 \Ch{Declarations}{Decl}
 \Sec{Attributes}{Decl.Attr}
 \Sub{Entry Attributes}{Decl.Attr.Entry}
+\Ch{Overloading}{Overload}
 \Ch{Runtime}{Runtime}