From e169c907f4634fe0e28e7caa6f2e80385cd5f4ca Mon Sep 17 00:00:00 2001
From: Zachary Snow <zach@zachjs.com>
Date: Mon, 13 Sep 2021 20:46:59 -0400
Subject: [PATCH] fix preprocessing of line comments not preceded by whitespace

---
 CHANGELOG.md                                    | 2 ++
 src/Language/SystemVerilog/Parser/Preprocess.hs | 3 +++
 test/lex/comment_no_space.sv                    | 5 +++++
 3 files changed, 10 insertions(+)
 create mode 100644 test/lex/comment_no_space.sv

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a2643e0..bc46ff6 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -26,6 +26,8 @@
   files encoding using Latin-1 with special characters in comments
 * Support for non-ANSI style port declarations where the port declaration is
   separate from the corresponding net or variable declaration
+* Fix preprocessing of line comments which are neither preceded nor followed by
+  whitespace except for the newline which terminates the comment
 
 ## v0.0.8
 
diff --git a/src/Language/SystemVerilog/Parser/Preprocess.hs b/src/Language/SystemVerilog/Parser/Preprocess.hs
index 8130cb0..0b0fb4e 100644
--- a/src/Language/SystemVerilog/Parser/Preprocess.hs
+++ b/src/Language/SystemVerilog/Parser/Preprocess.hs
@@ -951,4 +951,7 @@ removeThrough pattern = do
             let chars = patternIdx + length pattern
             let (dropped, rest) = splitAt chars str
             advancePositions dropped
+            when (pattern == "\n") $ do
+                pos <- getPosition
+                pushChar '\n' pos
             setInput rest
diff --git a/test/lex/comment_no_space.sv b/test/lex/comment_no_space.sv
new file mode 100644
index 0000000..39e0135
--- /dev/null
+++ b/test/lex/comment_no_space.sv
@@ -0,0 +1,5 @@
+module top;
+    initial begin
+        $display("Hi!");
+    end//comment
+endmodule