From 1f02ef82910f8c2b37a33cbfc0c347ebb10de9ae Mon Sep 17 00:00:00 2001
From: adamhutchings <adam.abahot@gmail.com>
Date: Sat, 12 Nov 2022 23:51:41 -0500
Subject: [PATCH 1/4] Add empty function test

---
 tests/sem/func-forward.yf | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 tests/sem/func-forward.yf

diff --git a/tests/sem/func-forward.yf b/tests/sem/func-forward.yf
new file mode 100644
index 0000000..0d30a14
--- /dev/null
+++ b/tests/sem/func-forward.yf
@@ -0,0 +1 @@
+foo(x: int): int;

From 97c2f845f20ea2d02c6c0032a8437458d8518e11 Mon Sep 17 00:00:00 2001
From: adamhutchings <adam.abahot@gmail.com>
Date: Sat, 12 Nov 2022 23:51:57 -0500
Subject: [PATCH 2/4] Handle empty function bodies properly

---
 src/api/cst-dump.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/api/cst-dump.c b/src/api/cst-dump.c
index 0c96f2b..26646ca 100644
--- a/src/api/cst-dump.c
+++ b/src/api/cst-dump.c
@@ -132,7 +132,11 @@ static void yf_dump_funcdecl(struct yfcs_funcdecl * node, FILE * out) {
     yf_print_line(out, "return type: %s", node->ret.databuf);
     yf_print_line(out, "function body");
     indent();
-    yf_dump_cst(node->body, out);
+    if (node->body) {
+        yf_dump_cst(node->body, out);
+    } else {
+        yf_print_line(out, "[no body]");
+    }
     dedent();
     yf_print_line(out, "end function body");
     dedent();

From a1756b5a84d3f63ee7145833232f815abc687d98 Mon Sep 17 00:00:00 2001
From: adamhutchings <adam.abahot@gmail.com>
Date: Sat, 12 Nov 2022 23:52:07 -0500
Subject: [PATCH 3/4] Generate empty function bodies properly

---
 src/gen/gen.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/src/gen/gen.c b/src/gen/gen.c
index 43c0ee5..e27ca2d 100644
--- a/src/gen/gen.c
+++ b/src/gen/gen.c
@@ -138,7 +138,10 @@ static void yf_gen_funcdecl(
 
     fprintf(out, ") ");
 
-    yf_gen_node(node->body, out, i);
+    if (node->body == NULL)
+        fprintf(out, ";");
+    else
+        yf_gen_node(node->body, out, i);
 
 }
 

From 70f67710416e3471b8e0f17734da698002b77632 Mon Sep 17 00:00:00 2001
From: adamhutchings <adam.abahot@gmail.com>
Date: Sat, 12 Nov 2022 23:52:24 -0500
Subject: [PATCH 4/4] Add frontend for empty function bodies

---
 src/parser/func.c                      | 11 +++++++
 src/semantics/validate/validate-func.c | 41 +++++++++++++++-----------
 2 files changed, 35 insertions(+), 17 deletions(-)

diff --git a/src/parser/func.c b/src/parser/func.c
index 0270a75..c04c4aa 100644
--- a/src/parser/func.c
+++ b/src/parser/func.c
@@ -88,6 +88,17 @@ int yfp_funcdecl(struct yf_parse_node * node, struct yf_lexer * lexer) {
 
 bodyp:
     node->type = YFCS_FUNCDECL;
+
+    struct yf_token sctest; /* semicolon test */
+    yfl_lex(lexer, &sctest);
+    if (sctest.type == YFT_SEMICOLON) {
+        /* No body for function. */
+        node->funcdecl.body = NULL;
+        return 0;
+    } else {
+        yfl_unlex(lexer, &sctest);
+    }
+
     node->funcdecl.body = yf_malloc(sizeof (struct yf_parse_node));
     return yfp_bstmt(node->funcdecl.body, lexer);
 
diff --git a/src/semantics/validate/validate-func.c b/src/semantics/validate/validate-func.c
index 1195d8c..ea3679c 100644
--- a/src/semantics/validate/validate-func.c
+++ b/src/semantics/validate/validate-func.c
@@ -67,29 +67,36 @@ int validate_funcdecl(
         return 1;
     }
 
-    a->body = yf_malloc(sizeof (struct yf_ast_node));
-    if (!a->body)
-        return 2;
-
-    /* Now, validate the body. */
-    if (validate_bstmt(validator, c->body, a->body, a->ret, &returns)) {
-        yf_free(a->body);
+    if (c->body == NULL) {
         a->body = NULL;
-        return 1;
+    } else {
+        a->body = yf_malloc(sizeof (struct yf_ast_node));
+        if (!a->body)
+            return 2;
+
+        /* Now, validate the body. */
+        if (validate_bstmt(validator, c->body, a->body, a->ret, &returns)) {
+            yf_free(a->body);
+            a->body = NULL;
+            return 1;
+        }
     }
 
+
     /* Close the scope. */
     exit_scope(validator);
 
-    if (returns == 0 && a->ret->primitive.size != 0) {
-        YF_PRINT_ERROR(
-            "%s %d:%d: Function '%s' does not always return a value",
-            cin->loc.file,
-            cin->loc.line,
-            cin->loc.column,
-            c->name.name
-        );
-        return 1;
+    if (a->body != NULL) {
+        if (returns == 0 && a->ret->primitive.size != 0) {
+            YF_PRINT_ERROR(
+                "%s %d:%d: Function '%s' does not always return a value",
+                cin->loc.file,
+                cin->loc.line,
+                cin->loc.column,
+                c->name.name
+            );
+            return 1;
+        }
     }
 
     return 0;