From 328e34077a2017d4017f907ac69c7ed5d6c160d4 Mon Sep 17 00:00:00 2001
From: David Phillips <david@sighup.nz>
Date: Wed, 1 Aug 2018 20:21:37 +1200
Subject: Trim leading whitespace from contextual error, detect EOF

Side-note that the token location tuple maintains the correct column
number to include the whitespace in the source file. Side-side note:
tabs are counted as one column but many editors will count them as
whatever the tabstop/tabwidth is.
---
 parser.c | 30 ++++++++++++++++++++++++------
 1 file changed, 24 insertions(+), 6 deletions(-)

(limited to 'parser.c')

diff --git a/parser.c b/parser.c
index 618df1a..f16af6c 100644
--- a/parser.c
+++ b/parser.c
@@ -14,9 +14,16 @@ static FILE* fd;
 static struct token *cursor;
 static const char *filename;
 
-#define emit(...) fprintf(stderr, "%s at (%zd,%zd): ", filename, cursor->loc.line, cursor->loc.column);\
-                  fprintf(stderr, __VA_ARGS__);\
-                  indicate_file_area(fd, cursor->loc.line, cursor->loc.column, cursor->span)
+/* FIXME change to varadic fuction */
+#define emit(...) \
+    if (cursor) { \
+        fprintf(stderr, "%s at (%zd,%zd): ", filename, cursor->loc.line, cursor->loc.column); \
+        fprintf(stderr, __VA_ARGS__); \
+        indicate_file_area(fd, cursor->loc.line, cursor->loc.column - cursor->loc.leading_whitespace_len, cursor->span); \
+    } else { \
+        fprintf(stderr, "%s: ", filename); \
+        fprintf(stderr, __VA_ARGS__); \
+    }
 
 
 //static struct op_lookup uop_handlers[] = {
@@ -42,9 +49,13 @@ expect(enum TOKEN_TYPE e) {
 	char *expected_desc = "(internal error)";
 	char *observed_desc = "(internal error)";
 
-	if (cursor->type != e) {
+	if (!cursor || cursor->type != e) {
 		expected_desc = get_token_description(e);
-		observed_desc = get_token_description(cursor->type);
+		if (cursor) {
+			observed_desc = get_token_description(cursor->type);
+		} else {
+			observed_desc = "end of file";
+		}
 		emit("Error: Expected %s, got %s\n", expected_desc, observed_desc);
 		return 1;
 	}
@@ -54,7 +65,9 @@ expect(enum TOKEN_TYPE e) {
 
 static void
 kerchunk() {
-	cursor = cursor->next;
+	if (cursor) {
+		cursor = cursor->next;
+	}
 }
 
 int
@@ -64,6 +77,11 @@ parse(const char *fname, FILE *f, struct token *t) {
 	filename = fname;
 	cursor = t;
 
+	/* Eat leading EOL tokens */
+	while (cursor && cursor->type == TOK_EOL) {
+		kerchunk();
+	}
+
 	if (expect(TOK_MODULE)) {
 		return 1;
 	}
-- 
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