From 57629478a15249b4fc4bbffe534c2540e61607d3 Mon Sep 17 00:00:00 2001
From: hyung-hwan <hyunghwan.chung@gmail.com>
Date: Tue, 28 Nov 2023 20:47:23 +0900
Subject: [PATCH] some 'do' experiment

---
 README.md     |  7 +++++++
 lib/comp.c    | 20 +++++++++++++++++++-
 t/Makefile.am |  1 +
 t/Makefile.in |  1 +
 4 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 3cd878f..7238cd2 100644
--- a/README.md
+++ b/README.md
@@ -25,6 +25,13 @@ A HCL program is composed of expressions.
 - until
 - while
 
+### do
+
+```
+do;
+do 10;
+do { | k | set k 20; printf "k=%d\n" k };
+```
 
 ## Literals
 - integer
diff --git a/lib/comp.c b/lib/comp.c
index 6018c25..fb9de33 100644
--- a/lib/comp.c
+++ b/lib/comp.c
@@ -24,6 +24,10 @@
 
 #include "hcl-prv.h"
 
+/* limit the `do` expression to have not more than 1 expression and
+ * no variable declaration if not enclosed in parentheses */
+#define LANG_LIMIT_DO
+
 enum
 {
 	VAR_NAMED,
@@ -1707,7 +1711,6 @@ static HCL_INLINE int compile_or_p2 (hcl_t* hcl)
 
 /* ========================================================================= */
 
-
 /* EXPERIMENT WITH BINOP */
 static int compile_plus (hcl_t* hcl, hcl_cnode_t* src)
 {
@@ -2004,6 +2007,7 @@ static int compile_expression_block (hcl_t* hcl, hcl_cnode_t* src, const hcl_bch
 			return -1;
 		}
 
+#if defined(LANG_LIMIT_DO) /* this limitation doesn't seem really useful? or make it #pragma based? */
 		if (!(flags & CEB_IS_BLOCK) && (flags & CEB_AUTO_FORGED))
 		{
 			/* `do` not explicitly enclosed in ().
@@ -2016,6 +2020,7 @@ static int compile_expression_block (hcl_t* hcl, hcl_cnode_t* src, const hcl_bch
 				"variable declaration disallowed in %hs context", ctxname);
 			return -1;
 		}
+#endif
 	}
 
 	tvslen = hcl->c->tv.s.len;
@@ -2033,6 +2038,19 @@ static int compile_expression_block (hcl_t* hcl, hcl_cnode_t* src, const hcl_bch
 		}
 	}
 
+#if defined(LANG_LIMIT_DO)
+	if (!(flags & CEB_IS_BLOCK) && (flags & CEB_AUTO_FORGED))
+	{
+		if (obj && HCL_CNODE_IS_CONS(obj) && hcl_countcnodecons(hcl, obj) != 1)
+		{
+			hcl_setsynerrbfmt (
+				hcl, HCL_SYNERR_VARDCLBANNED, HCL_CNODE_GET_LOC(obj), HCL_NULL,
+				"more than one expression after %hs", ctxname);
+			return -1;
+		}
+	}
+#endif
+
 	fbi = &hcl->c->fnblk.info[hcl->c->fnblk.depth];
 	fbi->tmprlen = hcl->c->tv.s.len;
 	fbi->tmprcnt = hcl->c->tv.wcount;
diff --git a/t/Makefile.am b/t/Makefile.am
index 67d94c3..929c1e5 100644
--- a/t/Makefile.am
+++ b/t/Makefile.am
@@ -10,6 +10,7 @@ check_SCRIPTS = \
 
 check_ERRORS = \
 	do-01.err \
+	do-02.err \
 	feed-01.err \
 	var-01.err \
 	var-02.err \
diff --git a/t/Makefile.in b/t/Makefile.in
index d145a27..150455c 100644
--- a/t/Makefile.in
+++ b/t/Makefile.in
@@ -481,6 +481,7 @@ check_SCRIPTS = \
 
 check_ERRORS = \
 	do-01.err \
+	do-02.err \
 	feed-01.err \
 	var-01.err \
 	var-02.err \