From 2b5755178ff206978b0d587458669be4ca976c0f Mon Sep 17 00:00:00 2001
From: nella <simontupy64@gmail.com>
Date: Wed, 29 Jul 2026 11:02:59 +0200
Subject: [PATCH] Clean up diagnostics.

---
 frontends/verilog/const2ast.cc       | 14 ++++++++++----
 frontends/verilog/verilog_frontend.h |  2 ++
 tests/various/const_cmdline.ys       | 15 +++++++++++++++
 3 files changed, 27 insertions(+), 4 deletions(-)
 create mode 100644 tests/various/const_cmdline.ys

diff --git a/frontends/verilog/const2ast.cc b/frontends/verilog/const2ast.cc
index 43d36cf2f..7093b97ee 100644
--- a/frontends/verilog/const2ast.cc
+++ b/frontends/verilog/const2ast.cc
@@ -45,13 +45,17 @@ using namespace AST;
 using namespace VERILOG_FRONTEND;
 
 void ConstParser::log_maybe_loc_error(std::string msg) {
-	log_file_error(loc.begin.filename ? loc.begin.filename->c_str() : "INTERNAL",
-    loc.begin.line, "%s", msg);
+	if (loc.begin.filename)
+		log_file_error(*loc.begin.filename, loc.begin.line, "%s", msg);
+	else
+		log_error("Failed to parse constant `%s': %s", code_str, msg);
 }
 
 void ConstParser::log_maybe_loc_warn(std::string msg) {
-	log_file_warning(loc.begin.filename ? loc.begin.filename->c_str() : "INTERNAL",
-    loc.begin.line, "%s", msg);
+	if (loc.begin.filename)
+		log_file_warning(*loc.begin.filename, loc.begin.line, "%s", msg);
+	else
+		log_warning("While parsing constant `%s': %s", code_str, msg);
 }
 
 // divide an arbitrary length decimal number by two and return the rest
@@ -160,6 +164,8 @@ void ConstParser::my_strtobin(std::vector<RTLIL::State> &data, const char *str,
 // convert the Verilog code for a constant to an AST node
 std::unique_ptr<AstNode> ConstParser::const2ast(std::string code, char case_type, bool warn_z)
 {
+	code_str = code;
+
 	if (warn_z) {
 		auto ret = const2ast(code, case_type);
 		if (ret != nullptr && std::find(ret->bits.begin(), ret->bits.end(), RTLIL::State::Sz) != ret->bits.end())
diff --git a/frontends/verilog/verilog_frontend.h b/frontends/verilog/verilog_frontend.h
index 83c0e37a1..112f0977a 100644
--- a/frontends/verilog/verilog_frontend.h
+++ b/frontends/verilog/verilog_frontend.h
@@ -42,6 +42,8 @@ namespace VERILOG_FRONTEND
 	/* Ephemeral context class */
 	struct ConstParser {
 		AST::AstSrcLocType loc;
+		// original constant text, used in diagnostics when loc has no source file
+		std::string code_str = {};
 	private:
 		void log_maybe_loc_error(std::string msg);
 		void log_maybe_loc_warn(std::string msg);
diff --git a/tests/various/const_cmdline.ys b/tests/various/const_cmdline.ys
new file mode 100644
index 000000000..5874c2ecf
--- /dev/null
+++ b/tests/various/const_cmdline.ys
@@ -0,0 +1,15 @@
+# https://github.com/YosysHQ/yosys/issues/6009
+read_verilog <<EOT
+module top(output [7:0] o);
+assign o = 8'hAA;
+endmodule
+EOT
+prep -top top
+
+# width mismatch
+logger -expect warning "While parsing constant `2'd7'" 1
+setattr -set foo 2'd7 t:*
+
+# multi-bit unsized const
+logger -expect error "Failed to parse constant `8'00000101'" 1
+setattr -set foo 8'00000101 t:*