properly handle duplicate names in vcd

crates/fayalite/src/sim/vcd.rs

@@ -5,6 +5,7 @@ use crate::{
     enum_::{Enum, EnumType},
     expr::Flow,
     int::UInt,
+    intern::{Intern, Interned},
     sim::{
         time::{SimDuration, SimInstant},
         TraceArray, TraceAsyncReset, TraceBool, TraceBundle, TraceClock, TraceDecl,
@@ -15,12 +16,73 @@ use crate::{
     },
 };
 use bitvec::{order::Lsb0, slice::BitSlice};
+use hashbrown::{hash_map::Entry, HashMap};
 use std::{
-    fmt,
+    fmt::{self, Write as _},
-    io::{self, Write},
+    io, mem,
-    mem,
 };
 
+#[derive(Default)]
+struct Scope {
+    last_inserted: HashMap<Interned<str>, usize>,
+}
+
+#[derive(Copy, Clone)]
+struct VerilogIdentifier {
+    unescaped_name: Interned<str>,
+}
+
+impl VerilogIdentifier {
+    fn needs_escape(self) -> bool {
+        // we only allow ascii, so we can just check bytes
+        let Some((&first, rest)) = self.unescaped_name.as_bytes().split_first() else {
+            unreachable!("Scope::new_identifier guarantees a non-empty name");
+        };
+        if !first.is_ascii_alphabetic() && first != b'_' {
+            true
+        } else {
+            rest.iter()
+                .any(|&ch| !ch.is_ascii_alphanumeric() && ch != b'_' && ch != b'$')
+        }
+    }
+}
+
+impl fmt::Display for VerilogIdentifier {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        if self.needs_escape() {
+            f.write_str("\\")?;
+        }
+        write!(f, "{}", Escaped(self.unescaped_name))
+    }
+}
+
+impl Scope {
+    fn new_identifier(&mut self, unescaped_name: Interned<str>) -> VerilogIdentifier {
+        let next_disambiguator = match self.last_inserted.entry(unescaped_name) {
+            Entry::Vacant(entry) => {
+                entry.insert(1);
+                return VerilogIdentifier { unescaped_name };
+            }
+            Entry::Occupied(entry) => entry.get() + 1,
+        };
+        let mut disambiguated_name = String::from(&*unescaped_name);
+        for disambiguator in next_disambiguator.. {
+            disambiguated_name.truncate(unescaped_name.len());
+            write!(disambiguated_name, "_{disambiguator}").expect("can't fail");
+            if let Entry::Vacant(entry) = self.last_inserted.entry((*disambiguated_name).intern()) {
+                let retval = VerilogIdentifier {
+                    unescaped_name: *entry.key(),
+                };
+                entry.insert(1);
+                // speed up future searches
+                self.last_inserted.insert(unescaped_name, disambiguator);
+                return retval;
+            }
+        }
+        panic!("too many names");
+    }
+}
+
 pub struct VcdWriterDecls<W: io::Write + 'static> {
     writer: W,
     timescale: SimDuration,
@@ -97,14 +159,20 @@ impl<W: io::Write> fmt::Debug for VcdWriterDecls<W> {
     }
 }
 
+/// pass in scope to ensure it's not available in child scope
 fn write_vcd_scope<W: io::Write, R>(
     writer: &mut W,
     scope_type: &str,
-    scope_name: &str,
+    scope_name: Interned<str>,
-    f: impl FnOnce(&mut W) -> io::Result<R>,
+    scope: &mut Scope,
+    f: impl FnOnce(&mut W, &mut Scope) -> io::Result<R>,
 ) -> io::Result<R> {
-    writeln!(writer, "$scope {scope_type} {scope_name} $end")?;
+    writeln!(
-    let retval = f(writer)?;
+        writer,
+        "$scope {scope_type} {} $end",
+        scope.new_identifier(scope_name),
+    )?;
+    let retval = f(writer, &mut Scope::default())?;
     writeln!(writer, "$upscope $end")?;
     Ok(retval)
 }
@@ -143,24 +211,28 @@ trait_arg! {
 
 struct ArgModule<'a> {
     properties: &'a mut VcdWriterProperties,
+    scope: &'a mut Scope,
 }
 
 impl<'a> ArgModule<'a> {
     fn reborrow(&mut self) -> ArgModule<'_> {
         ArgModule {
             properties: self.properties,
+            scope: self.scope,
         }
     }
 }
 
 struct ArgModuleBody<'a> {
     properties: &'a mut VcdWriterProperties,
+    scope: &'a mut Scope,
 }
 
 impl<'a> ArgModuleBody<'a> {
     fn reborrow(&mut self) -> ArgModuleBody<'_> {
         ArgModuleBody {
             properties: self.properties,
+            scope: self.scope,
         }
     }
 }
@@ -170,6 +242,7 @@ struct ArgInType<'a> {
     sink_var_type: &'static str,
     duplex_var_type: &'static str,
     properties: &'a mut VcdWriterProperties,
+    scope: &'a mut Scope,
 }
 
 impl<'a> ArgInType<'a> {
@@ -179,6 +252,7 @@ impl<'a> ArgInType<'a> {
             sink_var_type: self.sink_var_type,
             duplex_var_type: self.duplex_var_type,
             properties: self.properties,
+            scope: self.scope,
         }
     }
 }
@@ -226,55 +300,42 @@ fn write_vcd_id<W: io::Write>(writer: &mut W, mut id: usize) -> io::Result<()> {
     Ok(())
 }
 
-fn write_escaped<W: io::Write>(writer: &mut W, value: impl fmt::Display) -> io::Result<()> {
+struct Escaped<T: fmt::Display>(T);
-    // escaping rules from function GTKWave uses to decode VCD strings:
+
-    // https://github.com/gtkwave/gtkwave/blob/491f24d7e8619cfc1fcc65704ee5c967d1083c18/lib/libfst/fstapi.c#L7090
+impl<T: fmt::Display> fmt::Display for Escaped<T> {
-    struct Wrapper<W>(W);
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-    impl<W: io::Write> io::Write for Wrapper<W> {
+        // escaping rules from function GTKWave uses to decode VCD strings:
-        fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        // https://github.com/gtkwave/gtkwave/blob/491f24d7e8619cfc1fcc65704ee5c967d1083c18/lib/libfst/fstapi.c#L7090
-            if buf.is_empty() {
+        struct Wrapper<W>(W);
-                return self.0.write(buf);
+        impl<W: fmt::Write> fmt::Write for Wrapper<W> {
-            }
+            fn write_str(&mut self, s: &str) -> fmt::Result {
-            let mut retval = 0;
+                for byte in s.bytes() {
-            for &byte in buf {
+                    match byte {
-                match byte {
+                        b'\\' | b'\'' | b'"' | b'?' => {
-                    b'\\' | b'\'' | b'"' | b'?' => self.0.write_all(&[b'\\', byte])?,
+                            self.0.write_str("\\")?;
-                    b'\n' => self.0.write_all(br"\n")?,
+                            self.0.write_char(byte as char)?;
-                    b'\r' => self.0.write_all(br"\r")?,
+                        }
-                    b'\t' => self.0.write_all(br"\t")?,
+                        b'\n' => self.0.write_str(r"\n")?,
-                    0x7 => self.0.write_all(br"\a")?,
+                        b'\r' => self.0.write_str(r"\r")?,
-                    0x8 => self.0.write_all(br"\b")?,
+                        b'\t' => self.0.write_str(r"\t")?,
-                    0xC => self.0.write_all(br"\f")?,
+                        0x7 => self.0.write_str(r"\a")?,
-                    0xB => self.0.write_all(br"\v")?,
+                        0x8 => self.0.write_str(r"\b")?,
-                    _ => {
+                        0xC => self.0.write_str(r"\f")?,
-                        if byte.is_ascii_graphic() {
+                        0xB => self.0.write_str(r"\v")?,
-                            self.0.write_all(&[byte])?;
+                        _ => {
-                        } else {
+                            if byte.is_ascii_graphic() {
-                            write!(self.0, r"\x{byte:02x}")?;
+                                self.0.write_char(byte as char)?;
+                            } else {
+                                write!(self.0, r"\x{byte:02x}")?;
+                            }
                         }
                     }
                 }
-                retval += 1;
+                Ok(())
             }
-            Ok(retval)
-        }
-
-        fn flush(&mut self) -> io::Result<()> {
-            self.0.flush()
         }
+        write!(Wrapper(f), "{}", self.0)
     }
-    write!(Wrapper(writer), "{value}")
-}
-
-fn is_unescaped_verilog_identifier(ident: &str) -> bool {
-    // we only allow ascii, so we can just check bytes
-    let Some((&first, rest)) = ident.as_bytes().split_first() else {
-        return false; // empty string is not an identifier
-    };
-    (first.is_ascii_alphabetic() || first == b'_')
-        && rest
-            .iter()
-            .all(|&ch| ch.is_ascii_alphanumeric() || ch == b'_' || ch == b'$')
 }
 
 fn write_vcd_var<W: io::Write>(
@@ -284,7 +345,7 @@ fn write_vcd_var<W: io::Write>(
     var_type: &str,
     size: usize,
     location: TraceLocation,
-    name: &str,
+    name: VerilogIdentifier,
 ) -> io::Result<()> {
     let id = match location {
         TraceLocation::Scalar(id) => id.as_usize(),
@@ -319,12 +380,7 @@ fn write_vcd_var<W: io::Write>(
     };
     write!(writer, "$var {var_type} {size} ")?;
     write_vcd_id(writer, id)?;
-    writer.write_all(b" ")?;
+    writeln!(writer, " {name} $end")
-    if !is_unescaped_verilog_identifier(name) {
-        writer.write_all(b"\\")?;
-    }
-    write_escaped(writer, name)?;
-    writer.write_all(b" $end\n")
 }
 
 impl WriteTrace for TraceUInt {
@@ -334,6 +390,7 @@ impl WriteTrace for TraceUInt {
             sink_var_type,
             duplex_var_type,
             properties,
+            scope,
         } = arg.in_type();
         let Self {
             location,
@@ -356,7 +413,7 @@ impl WriteTrace for TraceUInt {
             var_type,
             ty.width(),
             location,
-            &name,
+            scope.new_identifier(name),
         )
     }
 }
@@ -421,6 +478,7 @@ impl WriteTrace for TraceEnumDiscriminant {
             sink_var_type: _,
             duplex_var_type: _,
             properties,
+            scope,
         } = arg.in_type();
         let Self {
             location,
@@ -435,7 +493,7 @@ impl WriteTrace for TraceEnumDiscriminant {
             "string",
             1,
             location,
-            &name,
+            scope.new_identifier(name),
         )
     }
 }
@@ -507,11 +565,11 @@ impl WriteTrace for TraceScope {
 
 impl WriteTrace for TraceModule {
     fn write_trace<W: io::Write, A: Arg>(self, writer: &mut W, mut arg: A) -> io::Result<()> {
-        let ArgModule { properties } = arg.module();
+        let ArgModule { properties, scope } = arg.module();
         let Self { name, children } = self;
-        write_vcd_scope(writer, "module", &name, |writer| {
+        write_vcd_scope(writer, "module", name, scope, |writer, scope| {
             for child in children {
-                child.write_trace(writer, ArgModuleBody { properties })?;
+                child.write_trace(writer, ArgModuleBody { properties, scope })?;
             }
             Ok(())
         })
@@ -520,7 +578,7 @@ impl WriteTrace for TraceModule {
 
 impl WriteTrace for TraceInstance {
     fn write_trace<W: io::Write, A: Arg>(self, writer: &mut W, mut arg: A) -> io::Result<()> {
-        let ArgModuleBody { properties } = arg.module_body();
+        let ArgModuleBody { properties, scope } = arg.module_body();
         let Self {
             name: _,
             instance_io,
@@ -534,15 +592,16 @@ impl WriteTrace for TraceInstance {
                 sink_var_type: "wire",
                 duplex_var_type: "wire",
                 properties,
+                scope,
             },
         )?;
-        module.write_trace(writer, ArgModule { properties })
+        module.write_trace(writer, ArgModule { properties, scope })
     }
 }
 
 impl WriteTrace for TraceMem {
     fn write_trace<W: io::Write, A: Arg>(self, writer: &mut W, mut arg: A) -> io::Result<()> {
-        let ArgModuleBody { properties } = arg.module_body();
+        let ArgModuleBody { properties, scope } = arg.module_body();
         let Self {
             id,
             name,
@@ -551,27 +610,41 @@ impl WriteTrace for TraceMem {
             ports,
             array_type,
         } = self;
-        write_vcd_scope(writer, "struct", &*name, |writer| {
+        write_vcd_scope(writer, "struct", name, scope, |writer, scope| {
-            write_vcd_scope(writer, "struct", "contents", |writer| {
+            write_vcd_scope(
-                for element_index in 0..array_type.len() {
+                writer,
-                    write_vcd_scope(writer, "struct", &format!("[{element_index}]"), |writer| {
+                "struct",
-                        properties.memory_properties[id.as_usize()].element_index = element_index;
+                "contents".intern(),
-                        properties.memory_properties[id.as_usize()].element_part_index = 0;
+                scope,
-                        element_type.write_trace(
+                |writer, scope| {
+                    for element_index in 0..array_type.len() {
+                        write_vcd_scope(
                             writer,
-                            ArgInType {
+                            "struct",
-                                source_var_type: "reg",
+                            Intern::intern_owned(format!("[{element_index}]")),
-                                sink_var_type: "reg",
+                            scope,
-                                duplex_var_type: "reg",
+                            |writer, scope| {
-                                properties,
+                                properties.memory_properties[id.as_usize()].element_index =
+                                    element_index;
+                                properties.memory_properties[id.as_usize()].element_part_index = 0;
+                                element_type.write_trace(
+                                    writer,
+                                    ArgInType {
+                                        source_var_type: "reg",
+                                        sink_var_type: "reg",
+                                        duplex_var_type: "reg",
+                                        properties,
+                                        scope,
+                                    },
+                                )
                             },
-                        )
+                        )?;
-                    })?;
+                    }
-                }
+                    Ok(())
-                Ok(())
+                },
-            })?;
+            )?;
             for port in ports {
-                port.write_trace(writer, ArgModuleBody { properties })?;
+                port.write_trace(writer, ArgModuleBody { properties, scope })?;
             }
             Ok(())
         })
@@ -580,7 +653,7 @@ impl WriteTrace for TraceMem {
 
 impl WriteTrace for TraceMemPort {
     fn write_trace<W: io::Write, A: Arg>(self, writer: &mut W, mut arg: A) -> io::Result<()> {
-        let ArgModuleBody { properties } = arg.module_body();
+        let ArgModuleBody { properties, scope } = arg.module_body();
         let Self {
             name: _,
             bundle,
@@ -593,6 +666,7 @@ impl WriteTrace for TraceMemPort {
                 sink_var_type: "wire",
                 duplex_var_type: "wire",
                 properties,
+                scope,
             },
         )
     }
@@ -600,7 +674,7 @@ impl WriteTrace for TraceMemPort {
 
 impl WriteTrace for TraceWire {
     fn write_trace<W: io::Write, A: Arg>(self, writer: &mut W, mut arg: A) -> io::Result<()> {
-        let ArgModuleBody { properties } = arg.module_body();
+        let ArgModuleBody { properties, scope } = arg.module_body();
         let Self {
             name: _,
             child,
@@ -613,6 +687,7 @@ impl WriteTrace for TraceWire {
                 sink_var_type: "wire",
                 duplex_var_type: "wire",
                 properties,
+                scope,
             },
         )
     }
@@ -620,7 +695,7 @@ impl WriteTrace for TraceWire {
 
 impl WriteTrace for TraceReg {
     fn write_trace<W: io::Write, A: Arg>(self, writer: &mut W, mut arg: A) -> io::Result<()> {
-        let ArgModuleBody { properties } = arg.module_body();
+        let ArgModuleBody { properties, scope } = arg.module_body();
         let Self {
             name: _,
             child,
@@ -633,6 +708,7 @@ impl WriteTrace for TraceReg {
                 sink_var_type: "reg",
                 duplex_var_type: "reg",
                 properties,
+                scope,
             },
         )
     }
@@ -640,7 +716,7 @@ impl WriteTrace for TraceReg {
 
 impl WriteTrace for TraceModuleIO {
     fn write_trace<W: io::Write, A: Arg>(self, writer: &mut W, mut arg: A) -> io::Result<()> {
-        let ArgModuleBody { properties } = arg.module_body();
+        let ArgModuleBody { properties, scope } = arg.module_body();
         let Self {
             name: _,
             child,
@@ -654,6 +730,7 @@ impl WriteTrace for TraceModuleIO {
                 sink_var_type: "wire",
                 duplex_var_type: "wire",
                 properties,
+                scope,
             },
         )
     }
@@ -661,16 +738,31 @@ impl WriteTrace for TraceModuleIO {
 
 impl WriteTrace for TraceBundle {
     fn write_trace<W: io::Write, A: Arg>(self, writer: &mut W, mut arg: A) -> io::Result<()> {
-        let mut arg = arg.in_type();
+        let ArgInType {
+            source_var_type,
+            sink_var_type,
+            duplex_var_type,
+            properties,
+            scope,
+        } = arg.in_type();
         let Self {
             name,
             fields,
             ty: _,
             flow: _,
         } = self;
-        write_vcd_scope(writer, "struct", &name, |writer| {
+        write_vcd_scope(writer, "struct", name, scope, |writer, scope| {
             for field in fields {
-                field.write_trace(writer, arg.reborrow())?;
+                field.write_trace(
+                    writer,
+                    ArgInType {
+                        source_var_type,
+                        sink_var_type,
+                        duplex_var_type,
+                        properties,
+                        scope,
+                    },
+                )?;
             }
             Ok(())
         })
@@ -679,16 +771,31 @@ impl WriteTrace for TraceBundle {
 
 impl WriteTrace for TraceArray {
     fn write_trace<W: io::Write, A: Arg>(self, writer: &mut W, mut arg: A) -> io::Result<()> {
-        let mut arg = arg.in_type();
+        let ArgInType {
+            source_var_type,
+            sink_var_type,
+            duplex_var_type,
+            properties,
+            scope,
+        } = arg.in_type();
         let Self {
             name,
             elements,
             ty: _,
             flow: _,
         } = self;
-        write_vcd_scope(writer, "struct", &name, |writer| {
+        write_vcd_scope(writer, "struct", name, scope, |writer, scope| {
             for element in elements {
-                element.write_trace(writer, arg.reborrow())?;
+                element.write_trace(
+                    writer,
+                    ArgInType {
+                        source_var_type,
+                        sink_var_type,
+                        duplex_var_type,
+                        properties,
+                        scope,
+                    },
+                )?;
             }
             Ok(())
         })
@@ -697,7 +804,13 @@ impl WriteTrace for TraceArray {
 
 impl WriteTrace for TraceEnumWithFields {
     fn write_trace<W: io::Write, A: Arg>(self, writer: &mut W, mut arg: A) -> io::Result<()> {
-        let mut arg = arg.in_type();
+        let ArgInType {
+            source_var_type,
+            sink_var_type,
+            duplex_var_type,
+            properties,
+            scope,
+        } = arg.in_type();
         let Self {
             name,
             discriminant,
@@ -705,10 +818,28 @@ impl WriteTrace for TraceEnumWithFields {
             ty: _,
             flow: _,
         } = self;
-        write_vcd_scope(writer, "struct", &name, |writer| {
+        write_vcd_scope(writer, "struct", name, scope, |writer, scope| {
-            discriminant.write_trace(writer, arg.reborrow())?;
+            discriminant.write_trace(
+                writer,
+                ArgInType {
+                    source_var_type,
+                    sink_var_type,
+                    duplex_var_type,
+                    properties,
+                    scope,
+                },
+            )?;
             for field in non_empty_fields {
-                field.write_trace(writer, arg.reborrow())?;
+                field.write_trace(
+                    writer,
+                    ArgInType {
+                        source_var_type,
+                        sink_var_type,
+                        duplex_var_type,
+                        properties,
+                        scope,
+                    },
+                )?;
             }
             Ok(())
         })
@@ -744,6 +875,7 @@ impl<W: io::Write> TraceWriterDecls for VcdWriterDecls<W> {
             &mut writer,
             ArgModule {
                 properties: &mut properties,
+                scope: &mut Scope::default(),
             },
         )?;
         writeln!(writer, "$enddefinitions $end")?;
@@ -798,9 +930,7 @@ fn write_string_value_change(
     value: impl fmt::Display,
     id: usize,
 ) -> io::Result<()> {
-    writer.write_all(b"s")?;
+    write!(writer, "s{} ", Escaped(value))?;
-    write_escaped(writer, value)?;
-    writer.write_all(b" ")?;
     write_vcd_id(writer, id)?;
     writer.write_all(b"\n")
 }
@@ -946,3 +1076,49 @@ impl<W: io::Write> fmt::Debug for VcdWriter<W> {
             .finish_non_exhaustive()
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_scope() {
+        let mut scope = Scope::default();
+        assert_eq!(&*scope.new_identifier("foo".intern()).unescaped_name, "foo");
+        assert_eq!(
+            &*scope.new_identifier("foo_0".intern()).unescaped_name,
+            "foo_0"
+        );
+        assert_eq!(
+            &*scope.new_identifier("foo_1".intern()).unescaped_name,
+            "foo_1"
+        );
+        assert_eq!(
+            &*scope.new_identifier("foo_3".intern()).unescaped_name,
+            "foo_3"
+        );
+        assert_eq!(
+            &*scope.new_identifier("foo".intern()).unescaped_name,
+            "foo_2"
+        );
+        assert_eq!(
+            &*scope.new_identifier("foo".intern()).unescaped_name,
+            "foo_4"
+        );
+        assert_eq!(
+            &*scope.new_identifier("foo_0".intern()).unescaped_name,
+            "foo_0_2"
+        );
+        assert_eq!(
+            &*scope.new_identifier("foo_1".intern()).unescaped_name,
+            "foo_1_2"
+        );
+        for i in 5..1000u64 {
+            // verify it actually picks the next available identifier with no skips or duplicates
+            assert_eq!(
+                *scope.new_identifier("foo".intern()).unescaped_name,
+                format!("foo_{i}"),
+            );
+        }
+    }
+}

crates/fayalite/tests/sim.rs

@@ -1246,3 +1246,33 @@ fn test_memories3() {
         panic!();
     }
 }
+
+#[hdl_module(outline_generated)]
+pub fn duplicate_names() {
+    #[hdl]
+    let w = wire();
+    connect(w, 5u8);
+    #[hdl]
+    let w = wire();
+    connect(w, 6u8);
+}
+
+#[test]
+fn test_duplicate_names() {
+    let _n = SourceLocation::normalize_files_for_tests();
+    let mut sim = Simulation::new(duplicate_names());
+    let mut writer = RcWriter::default();
+    sim.add_trace_writer(VcdWriterDecls::new(writer.clone()));
+    sim.advance_time(SimDuration::from_micros(1));
+    sim.flush_traces().unwrap();
+    let vcd = String::from_utf8(writer.take()).unwrap();
+    println!("####### VCD:\n{vcd}\n#######");
+    if vcd != include_str!("sim/expected/duplicate_names.vcd") {
+        panic!();
+    }
+    let sim_debug = format!("{sim:#?}");
+    println!("#######\n{sim_debug}\n#######");
+    if sim_debug != include_str!("sim/expected/duplicate_names.txt") {
+        panic!();
+    }
+}

crates/fayalite/tests/sim/expected/duplicate_names.txt

@@ -0,0 +1,153 @@
+Simulation {
+    state: State {
+        insns: Insns {
+            state_layout: StateLayout {
+                ty: TypeLayout {
+                    small_slots: StatePartLayout<SmallSlots> {
+                        len: 0,
+                        debug_data: [],
+                        ..
+                    },
+                    big_slots: StatePartLayout<BigSlots> {
+                        len: 4,
+                        debug_data: [
+                            SlotDebugData {
+                                name: "InstantiatedModule(duplicate_names: duplicate_names).duplicate_names::w",
+                                ty: UInt<8>,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: UInt<8>,
+                            },
+                            SlotDebugData {
+                                name: "InstantiatedModule(duplicate_names: duplicate_names).duplicate_names::w",
+                                ty: UInt<8>,
+                            },
+                            SlotDebugData {
+                                name: "",
+                                ty: UInt<8>,
+                            },
+                        ],
+                        ..
+                    },
+                },
+                memories: StatePartLayout<Memories> {
+                    len: 0,
+                    debug_data: [],
+                    layout_data: [],
+                    ..
+                },
+            },
+            insns: [
+                // at: module-XXXXXXXXXX.rs:1:1
+                0: Const {
+                    dest: StatePartIndex<BigSlots>(3), // (0x6) SlotDebugData { name: "", ty: UInt<8> },
+                    value: 0x6,
+                },
+                // at: module-XXXXXXXXXX.rs:5:1
+                1: Copy {
+                    dest: StatePartIndex<BigSlots>(2), // (0x6) SlotDebugData { name: "InstantiatedModule(duplicate_names: duplicate_names).duplicate_names::w", ty: UInt<8> },
+                    src: StatePartIndex<BigSlots>(3), // (0x6) SlotDebugData { name: "", ty: UInt<8> },
+                },
+                // at: module-XXXXXXXXXX.rs:1:1
+                2: Const {
+                    dest: StatePartIndex<BigSlots>(1), // (0x5) SlotDebugData { name: "", ty: UInt<8> },
+                    value: 0x5,
+                },
+                // at: module-XXXXXXXXXX.rs:3:1
+                3: Copy {
+                    dest: StatePartIndex<BigSlots>(0), // (0x5) SlotDebugData { name: "InstantiatedModule(duplicate_names: duplicate_names).duplicate_names::w", ty: UInt<8> },
+                    src: StatePartIndex<BigSlots>(1), // (0x5) SlotDebugData { name: "", ty: UInt<8> },
+                },
+                // at: module-XXXXXXXXXX.rs:1:1
+                4: Return,
+            ],
+            ..
+        },
+        pc: 4,
+        memory_write_log: [],
+        memories: StatePart {
+            value: [],
+        },
+        small_slots: StatePart {
+            value: [],
+        },
+        big_slots: StatePart {
+            value: [
+                5,
+                5,
+                6,
+                6,
+            ],
+        },
+    },
+    io: Instance {
+        name: <simulator>::duplicate_names,
+        instantiated: Module {
+            name: duplicate_names,
+            ..
+        },
+    },
+    uninitialized_inputs: {},
+    io_targets: {},
+    made_initial_step: true,
+    needs_settle: false,
+    trace_decls: TraceModule {
+        name: "duplicate_names",
+        children: [
+            TraceWire {
+                name: "w",
+                child: TraceUInt {
+                    location: TraceScalarId(0),
+                    name: "w",
+                    ty: UInt<8>,
+                    flow: Duplex,
+                },
+                ty: UInt<8>,
+            },
+            TraceWire {
+                name: "w",
+                child: TraceUInt {
+                    location: TraceScalarId(1),
+                    name: "w",
+                    ty: UInt<8>,
+                    flow: Duplex,
+                },
+                ty: UInt<8>,
+            },
+        ],
+    },
+    traces: [
+        SimTrace {
+            id: TraceScalarId(0),
+            kind: BigUInt {
+                index: StatePartIndex<BigSlots>(0),
+                ty: UInt<8>,
+            },
+            state: 0x05,
+            last_state: 0x05,
+        },
+        SimTrace {
+            id: TraceScalarId(1),
+            kind: BigUInt {
+                index: StatePartIndex<BigSlots>(2),
+                ty: UInt<8>,
+            },
+            state: 0x06,
+            last_state: 0x06,
+        },
+    ],
+    trace_memories: {},
+    trace_writers: [
+        Running(
+            VcdWriter {
+                finished_init: true,
+                timescale: 1 ps,
+                ..
+            },
+        ),
+    ],
+    instant: 1 μs,
+    clocks_triggered: [],
+    ..
+}

crates/fayalite/tests/sim/expected/duplicate_names.vcd

@@ -0,0 +1,11 @@
+$timescale 1 ps $end
+$scope module duplicate_names $end
+$var wire 8 ! w $end
+$var wire 8 " w_2 $end
+$upscope $end
+$enddefinitions $end
+$dumpvars
+b101 !
+b110 "
+$end
+#1000000

crates/fayalite/tests/sim/expected/memories.vcd

@@ -24,97 +24,97 @@ $upscope $end
 $upscope $end
 $scope struct mem $end
 $scope struct contents $end
-$scope struct [0] $end
+$scope struct \[0] $end
 $scope struct mem $end
 $var reg 8 9 \0 $end
 $var reg 8 I \1 $end
 $upscope $end
 $upscope $end
-$scope struct [1] $end
+$scope struct \[1] $end
 $scope struct mem $end
 $var reg 8 : \0 $end
 $var reg 8 J \1 $end
 $upscope $end
 $upscope $end
-$scope struct [2] $end
+$scope struct \[2] $end
 $scope struct mem $end
 $var reg 8 ; \0 $end
 $var reg 8 K \1 $end
 $upscope $end
 $upscope $end
-$scope struct [3] $end
+$scope struct \[3] $end
 $scope struct mem $end
 $var reg 8 < \0 $end
 $var reg 8 L \1 $end
 $upscope $end
 $upscope $end
-$scope struct [4] $end
+$scope struct \[4] $end
 $scope struct mem $end
 $var reg 8 = \0 $end
 $var reg 8 M \1 $end
 $upscope $end
 $upscope $end
-$scope struct [5] $end
+$scope struct \[5] $end
 $scope struct mem $end
 $var reg 8 > \0 $end
 $var reg 8 N \1 $end
 $upscope $end
 $upscope $end
-$scope struct [6] $end
+$scope struct \[6] $end
 $scope struct mem $end
 $var reg 8 ? \0 $end
 $var reg 8 O \1 $end
 $upscope $end
 $upscope $end
-$scope struct [7] $end
+$scope struct \[7] $end
 $scope struct mem $end
 $var reg 8 @ \0 $end
 $var reg 8 P \1 $end
 $upscope $end
 $upscope $end
-$scope struct [8] $end
+$scope struct \[8] $end
 $scope struct mem $end
 $var reg 8 A \0 $end
 $var reg 8 Q \1 $end
 $upscope $end
 $upscope $end
-$scope struct [9] $end
+$scope struct \[9] $end
 $scope struct mem $end
 $var reg 8 B \0 $end
 $var reg 8 R \1 $end
 $upscope $end
 $upscope $end
-$scope struct [10] $end
+$scope struct \[10] $end
 $scope struct mem $end
 $var reg 8 C \0 $end
 $var reg 8 S \1 $end
 $upscope $end
 $upscope $end
-$scope struct [11] $end
+$scope struct \[11] $end
 $scope struct mem $end
 $var reg 8 D \0 $end
 $var reg 8 T \1 $end
 $upscope $end
 $upscope $end
-$scope struct [12] $end
+$scope struct \[12] $end
 $scope struct mem $end
 $var reg 8 E \0 $end
 $var reg 8 U \1 $end
 $upscope $end
 $upscope $end
-$scope struct [13] $end
+$scope struct \[13] $end
 $scope struct mem $end
 $var reg 8 F \0 $end
 $var reg 8 V \1 $end
 $upscope $end
 $upscope $end
-$scope struct [14] $end
+$scope struct \[14] $end
 $scope struct mem $end
 $var reg 8 G \0 $end
 $var reg 8 W \1 $end
 $upscope $end
 $upscope $end
-$scope struct [15] $end
+$scope struct \[15] $end
 $scope struct mem $end
 $var reg 8 H \0 $end
 $var reg 8 X \1 $end

crates/fayalite/tests/sim/expected/memories2.vcd

@@ -11,31 +11,31 @@ $var wire 1 ' wmask $end
 $upscope $end
 $scope struct mem $end
 $scope struct contents $end
-$scope struct [0] $end
+$scope struct \[0] $end
 $scope struct mem $end
 $var string 1 1 \$tag $end
 $var reg 1 6 HdlSome $end
 $upscope $end
 $upscope $end
-$scope struct [1] $end
+$scope struct \[1] $end
 $scope struct mem $end
 $var string 1 2 \$tag $end
 $var reg 1 7 HdlSome $end
 $upscope $end
 $upscope $end
-$scope struct [2] $end
+$scope struct \[2] $end
 $scope struct mem $end
 $var string 1 3 \$tag $end
 $var reg 1 8 HdlSome $end
 $upscope $end
 $upscope $end
-$scope struct [3] $end
+$scope struct \[3] $end
 $scope struct mem $end
 $var string 1 4 \$tag $end
 $var reg 1 9 HdlSome $end
 $upscope $end
 $upscope $end
-$scope struct [4] $end
+$scope struct \[4] $end
 $scope struct mem $end
 $var string 1 5 \$tag $end
 $var reg 1 : HdlSome $end

crates/fayalite/tests/sim/expected/memories3.vcd

@@ -42,7 +42,7 @@ $upscope $end
 $upscope $end
 $scope struct mem $end
 $scope struct contents $end
-$scope struct [0] $end
+$scope struct \[0] $end
 $scope struct mem $end
 $var reg 8 ] \[0] $end
 $var reg 8 e \[1] $end
@@ -54,7 +54,7 @@ $var reg 8 /" \[6] $end
 $var reg 8 7" \[7] $end
 $upscope $end
 $upscope $end
-$scope struct [1] $end
+$scope struct \[1] $end
 $scope struct mem $end
 $var reg 8 ^ \[0] $end
 $var reg 8 f \[1] $end
@@ -66,7 +66,7 @@ $var reg 8 0" \[6] $end
 $var reg 8 8" \[7] $end
 $upscope $end
 $upscope $end
-$scope struct [2] $end
+$scope struct \[2] $end
 $scope struct mem $end
 $var reg 8 _ \[0] $end
 $var reg 8 g \[1] $end
@@ -78,7 +78,7 @@ $var reg 8 1" \[6] $end
 $var reg 8 9" \[7] $end
 $upscope $end
 $upscope $end
-$scope struct [3] $end
+$scope struct \[3] $end
 $scope struct mem $end
 $var reg 8 ` \[0] $end
 $var reg 8 h \[1] $end
@@ -90,7 +90,7 @@ $var reg 8 2" \[6] $end
 $var reg 8 :" \[7] $end
 $upscope $end
 $upscope $end
-$scope struct [4] $end
+$scope struct \[4] $end
 $scope struct mem $end
 $var reg 8 a \[0] $end
 $var reg 8 i \[1] $end
@@ -102,7 +102,7 @@ $var reg 8 3" \[6] $end
 $var reg 8 ;" \[7] $end
 $upscope $end
 $upscope $end
-$scope struct [5] $end
+$scope struct \[5] $end
 $scope struct mem $end
 $var reg 8 b \[0] $end
 $var reg 8 j \[1] $end
@@ -114,7 +114,7 @@ $var reg 8 4" \[6] $end
 $var reg 8 <" \[7] $end
 $upscope $end
 $upscope $end
-$scope struct [6] $end
+$scope struct \[6] $end
 $scope struct mem $end
 $var reg 8 c \[0] $end
 $var reg 8 k \[1] $end
@@ -126,7 +126,7 @@ $var reg 8 5" \[6] $end
 $var reg 8 =" \[7] $end
 $upscope $end
 $upscope $end
-$scope struct [7] $end
+$scope struct \[7] $end
 $scope struct mem $end
 $var reg 8 d \[0] $end
 $var reg 8 l \[1] $end