A block comment must affirmatively end before end of source

wgsl/extract-grammar.py

@@ -426,6 +426,7 @@ def not_token_only(value):
     grammar_package.write('}\n')
 
 # External scanner for nested block comments
+# For the API, see https://tree-sitter.github.io/tree-sitter/creating-parsers#external-scanners
 # See: https://github.com/tree-sitter/tree-sitter-rust/blob/master/src/scanner.c
 
 os.makedirs(os.path.join(grammar_path, "src"), exist_ok=True)
@@ -461,6 +462,11 @@ def not_token_only(value):
     for (;;) {
       switch (lexer->lookahead) {
         case '\0':
+          /* This signals the end of input. Since nesting depth is
+           * greater than zero, the scanner is in the middle of
+           * a block comment. Block comments must be affirmatively
+           * terminated.
+           */
           return false;
         case '*':
           advance(lexer);

wgsl/index.bs

@@ -430,15 +430,25 @@ A <dfn noexport>block comment</dfn> is a kind of [=comment=] consisting of:
 * Then any sequence of:
     * A [=block comment=], or
     * Text that does not contain either `*/` or `/*`
-* Then either:
-    * The two characters `*/`, or
-    * The end of the source text.
+* Then the two characters `*/`
 
 Note: Block comments can be nested.
 Since a block comment requires matching start and end text sequences, and allows arbitrary nesting,
 a block comment cannot be recognized with a regular expression.
 This is a consequence of the Pumping Lemma for Regular Languages.
 
+<div class='example wgsl' heading='Comments'>
+  <xmp>
+  let f = 1.5;   // This is line-ending comment.
+  let g = 2.5;   /* This is a block comment
+                    that spans lines.
+                    /* Block comments can nest.
+                     */
+                    But all block comments must terminate.
+                  */
+  </xmp>
+</div>
+
 ## Tokens ## {#tokens}
 
 A <dfn>token</dfn> is a contiguous sequence of characters forming one of: