Small refactor of indentation lexer.

src/lex/indent.c

@@ -108,58 +108,53 @@ static uint32_t count_indents(enum indent_type type) {
     return counter;
 }
 
-static void new_indent(void) {
+// Returns `true` if a new indentation level was introduced.
+static _Bool new_indent(void) {
     struct indent indent = { 0, 0 };
     indent.tabs = count_indents(INDENT_TABS);
     indent.spaces = count_indents(INDENT_SPACES);
     char c = peekc();
-    if (c == '\t' && (indent.spaces > 0 || !tabs_allowed())) {
+    if ((indent.tabs > 0 && !tabs_allowed()) || (c == '\t' && indent.spaces > 0)) {
         fprintf(stderr, "lexical error: all tabs on a line must precede all spaces\n");
         exit(1);
     }
-    if (is_newline(c)) {
-        return;
-    }
-    if (indent_levels == MAX_INDENTS) {
+    if (indent_levels == MAX_INDENTS && !is_newline(c)) {
         fprintf(stderr, "lexical error: too many indentation levels! factor your code!\n");
         exit(1);
     }
     indents[indent_levels] = indent;
-    indent_levels++;
+    return indent.tabs > 0 || indent.spaces > 0;
 }
 
-int32_t lex_indentation(void) {
+uint32_t lex_line_indentation(void) {
     uint32_t indent_level = 0;
-    char c = peekc();
-    while (true) {
-        while (is_newline(c)) {
-            nextc();
-            c = peekc();
-        }
-        if (c == 0) {
-            indent_levels = 0;
+    while (indent_level < indent_levels) {
+        if (!is_indent(peekc())) {
             return indent_level;
         }
-        if (!is_indent(c)) {
-            break;
-        }
+        struct indent expected_indent = indents[indent_level];
+        expect_indent(INDENT_TABS, expected_indent.tabs);
+        expect_indent(INDENT_SPACES, expected_indent.spaces);
+        indent_level++;
+    }
+    if (new_indent()) {
+        return indent_level + 1;
+    }
+    return indent_level;
+}
+
+uint32_t lex_indentation(void) {
+    uint32_t indent_level;
+    while (true) {
+        indent_level = lex_line_indentation();
+        // We ignore trailing whitespace on empty lines,
+        // but don't know that a line will be empty until we've reached the end.
+        if (!is_newline(peekc())) { break; }
+        nextc();
+    }
+    if (peekc() == 0) {
+        // EOF closes all indentation-based blocks.
         indent_level = 0;
-        while (is_indent(c) && indent_level < indent_levels) {
-            struct indent indent = indents[indent_level];
-            expect_indent(INDENT_TABS, indent.tabs);
-            expect_indent(INDENT_SPACES, indent.spaces);
-            indent_level++;
-            c = peekc();
-        }
-        if (is_indent(c)) {
-            new_indent();
-            c = peekc();
-            if (!is_newline(c)) {
-                indent_levels++;
-                return indent_levels;
-            }
-        }
-        c = peekc();
     }
     indent_levels = indent_level;
     return indent_levels;

src/lex/indent.h

@@ -9,6 +9,6 @@
 _Bool is_newline(char c);
 _Bool is_indent(char c);
 
-int32_t lex_indentation(void);
+uint32_t lex_indentation(void);
 
 #endif