diff --git a/data/test.lang b/data/test.lang
index ba5a860..9f7fa75 100644
--- a/data/test.lang
+++ b/data/test.lang
@@ -1,33 +1,33 @@
 fn start() {
-    print("Helld!\n");
-    print("Hello World!!!!!\n");
-    thinger();
-    print("what\n");
-    exit(39);
+   print("Helld!\n");
+   print("Hello World!!!!!\n");
+   thinger();
+   print("what\n");
+   exit(39);
 }
 
 fn thinger() {
-    print("estamos jugando\n");
+   print("estamos jugando\n");
 }
 
 fn unused() {
-    print("el unused\n");
+   print("el unused\n");
 }
 
 fn print(msg: slice<8>) {
-    asm (a1 = msg) {
-        ld a2, 8, a1
-        ld a1, 0, a1
-        li a0, 1
-        li a7, 64
-        ecall
-    }
+   asm (a1 = msg) {
+      ld a2, 8, a1
+      ld a1, 0, a1
+      li a0, 1
+      li a7, 64
+      ecall
+   }
 }
 
 fn exit(status: 64) {
-    asm (a0 = status) {
-        ld a0, 0, a0
-        li a7, 93
-        ecall
-    };
+   asm (a0 = status) {
+      ld a0, 0, a0
+      li a7, 93
+      ecall
+   };
 }
diff --git a/src/ir/file.rs b/src/common/file.rs
similarity index 100%
rename from src/ir/file.rs
rename to src/common/file.rs
diff --git a/src/common/mod.rs b/src/common/mod.rs
new file mode 100644
index 0000000..7a3c486
--- /dev/null
+++ b/src/common/mod.rs
@@ -0,0 +1,5 @@
+mod output;
+mod file;
+
+pub use output::*;
+pub use file::*;
diff --git a/src/common/output.rs b/src/common/output.rs
new file mode 100644
index 0000000..87e42ea
--- /dev/null
+++ b/src/common/output.rs
@@ -0,0 +1,64 @@
+use super::{FilePos, FileSpan};
+
+#[derive(Debug, Clone)]
+pub struct CompilerMsg {
+    pub msg: String,
+    pub spans: Vec<FileSpan>,
+}
+
+pub struct CompilerOutput {
+    pub errs: Vec<CompilerMsg>,
+    pub hints: Vec<CompilerMsg>,
+}
+
+impl CompilerMsg {
+    pub fn from_msg(msg: String) -> Self {
+        Self {
+            msg,
+            spans: Vec::new(),
+        }
+    }
+    pub fn from_span(span: FileSpan, msg: String) -> Self {
+        Self {
+            msg,
+            spans: vec![span],
+        }
+    }
+    pub fn at(pos: FilePos, msg: String) -> Self {
+        Self {
+            msg,
+            spans: vec![FileSpan::at(pos)],
+        }
+    }
+    pub fn write_for(&self, ty: &str, writer: &mut impl std::io::Write, file: &str) -> std::io::Result<()> {
+        let after = if self.spans.is_empty() { "" } else { ":" };
+        writeln!(writer, "{}: {}{}", ty, self.msg, after)?;
+        for span in &self.spans {
+            span.write_for(writer, file)?;
+        }
+        Ok(())
+    }
+}
+
+impl CompilerOutput {
+    pub fn new() -> Self {
+        Self {
+            errs: Vec::new(),
+            hints: Vec::new(),
+        }
+    }
+    pub fn err(&mut self, msg: CompilerMsg) {
+        self.errs.push(msg);
+    }
+    pub fn hint(&mut self, msg: CompilerMsg) {
+        self.hints.push(msg);
+    }
+    pub fn write_for(&self, out: &mut impl std::io::Write, file: &str) {
+        for err in &self.errs {
+            err.write_for("error", out, file).unwrap();
+        }
+        for hint in &self.hints {
+            hint.write_for("hint", out, file).unwrap();
+        }
+    }
+}
diff --git a/src/compiler/arch/riscv64/asm.rs b/src/compiler/arch/riscv64/asm.rs
index d7d8422..6b76923 100644
--- a/src/compiler/arch/riscv64/asm.rs
+++ b/src/compiler/arch/riscv64/asm.rs
@@ -10,7 +10,13 @@ pub enum LinkerInstruction {
     Slli { dest: Reg, src: Reg, imm: i32 },
     Srli { dest: Reg, src: Reg, imm: i32 },
     Sd { src: Reg, offset: i32, base: Reg },
+    Sw { src: Reg, offset: i32, base: Reg },
+    Sh { src: Reg, offset: i32, base: Reg },
+    Sb { src: Reg, offset: i32, base: Reg },
     Ld { dest: Reg, offset: i32, base: Reg },
+    Lw { dest: Reg, offset: i32, base: Reg },
+    Lh { dest: Reg, offset: i32, base: Reg },
+    Lb { dest: Reg, offset: i32, base: Reg },
     Mv { dest: Reg, src: Reg },
     La { dest: Reg, src: Symbol },
     Jal { dest: Reg, offset: i32 },
@@ -36,7 +42,13 @@ impl Instr for LinkerInstruction {
             Self::Slli { dest, src, imm } => slli(*dest, *src, BitsI32::new(*imm)),
             Self::Srli { dest, src, imm } => srli(*dest, *src, BitsI32::new(*imm)),
             Self::Sd { src, offset, base } => sd(*src, BitsI32::new(*offset), *base),
+            Self::Sw { src, offset, base } => sw(*src, BitsI32::new(*offset), *base),
+            Self::Sh { src, offset, base } => sh(*src, BitsI32::new(*offset), *base),
+            Self::Sb { src, offset, base } => sb(*src, BitsI32::new(*offset), *base),
             Self::Ld { dest, offset, base } => ld(*dest, BitsI32::new(*offset), *base),
+            Self::Lw { dest, offset, base } => lw(*dest, BitsI32::new(*offset), *base),
+            Self::Lh { dest, offset, base } => lh(*dest, BitsI32::new(*offset), *base),
+            Self::Lb { dest, offset, base } => lb(*dest, BitsI32::new(*offset), *base),
             Self::Mv { dest, src } => addi(*dest, *src, BitsI32::new(0)),
             Self::La { dest, src } => {
                 if let Some(addr) = sym_map.get(*src) {
diff --git a/src/compiler/arch/riscv64/compile.rs b/src/compiler/arch/riscv64/compile.rs
index 93e1d80..9302055 100644
--- a/src/compiler/arch/riscv64/compile.rs
+++ b/src/compiler/arch/riscv64/compile.rs
@@ -4,7 +4,7 @@ use crate::{
     compiler::{arch::riscv64::Reg, create_program, Addr},
     ir::{
         arch::riscv64::{RV64Instruction as AI, RegRef},
-        IRLInstruction as IRI, IRLProgram, Len, Size, Symbol, VarID,
+        IRLInstruction as IRI, IRLProgram, Len, Size,
     },
 };
 
@@ -40,6 +40,54 @@ fn mov_mem(
         len -= 8;
         off += 8;
     }
+    while len >= 4 {
+        v.extend([
+            LI::Lw {
+                dest: temp,
+                offset: src_offset + off,
+                base: src,
+            },
+            LI::Sw {
+                src: temp,
+                offset: dest_offset + off,
+                base: dest,
+            },
+        ]);
+        len -= 4;
+        off += 4;
+    }
+    while len >= 2 {
+        v.extend([
+            LI::Lh {
+                dest: temp,
+                offset: src_offset + off,
+                base: src,
+            },
+            LI::Sh {
+                src: temp,
+                offset: dest_offset + off,
+                base: dest,
+            },
+        ]);
+        len -= 2;
+        off += 2;
+    }
+    while len >= 1 {
+        v.extend([
+            LI::Lb {
+                dest: temp,
+                offset: src_offset + off,
+                base: src,
+            },
+            LI::Sb {
+                src: temp,
+                offset: dest_offset + off,
+                base: dest,
+            },
+        ]);
+        len -= 1;
+        off += 1;
+    }
 }
 
 pub fn compile(program: IRLProgram) -> (Vec<u8>, Option<Addr>) {
diff --git a/src/compiler/arch/riscv64/single.rs b/src/compiler/arch/riscv64/single.rs
index b6e98db..a63f5d7 100644
--- a/src/compiler/arch/riscv64/single.rs
+++ b/src/compiler/arch/riscv64/single.rs
@@ -13,24 +13,33 @@ pub const fn ebreak() -> I {
 pub const fn auipc(dest: Reg, imm: BitsI32<31, 12>) -> I {
     u_type(imm.to_u(), dest, AUIPC)
 }
+
 pub const fn ld(dest: Reg, offset: BitsI32<11, 0>, base: Reg) -> I {
     i_type(offset.to_u(), base, width::D, dest, LOAD)
 }
 pub const fn lw(dest: Reg, offset: BitsI32<11, 0>, base: Reg) -> I {
     i_type(offset.to_u(), base, width::W, dest, LOAD)
 }
+pub const fn lh(dest: Reg, offset: BitsI32<11, 0>, base: Reg) -> I {
+    i_type(offset.to_u(), base, width::H, dest, LOAD)
+}
 pub const fn lb(dest: Reg, offset: BitsI32<11, 0>, base: Reg) -> I {
     i_type(offset.to_u(), base, width::B, dest, LOAD)
 }
+
+pub const fn sd(src: Reg, offset: BitsI32<11, 0>, base: Reg) -> I {
+    s_type(src, base, width::D, offset.to_u(), STORE)
+}
 pub const fn sb(src: Reg, offset: BitsI32<11, 0>, base: Reg) -> I {
     s_type(src, base, width::B, offset.to_u(), STORE)
 }
+pub const fn sh(src: Reg, offset: BitsI32<11, 0>, base: Reg) -> I {
+    s_type(src, base, width::H, offset.to_u(), STORE)
+}
 pub const fn sw(src: Reg, offset: BitsI32<11, 0>, base: Reg) -> I {
     s_type(src, base, width::W, offset.to_u(), STORE)
 }
-pub const fn sd(src: Reg, offset: BitsI32<11, 0>, base: Reg) -> I {
-    s_type(src, base, width::D, offset.to_u(), STORE)
-}
+
 pub const fn add(dest: Reg, src1: Reg, src2: Reg) -> I {
     r_type(Bits32::new(0), src2, src1, ADD, dest, OP)
 }
diff --git a/src/ir/arch/riscv64.rs b/src/ir/arch/riscv64.rs
index 55ed3dd..b36cfef 100644
--- a/src/ir/arch/riscv64.rs
+++ b/src/ir/arch/riscv64.rs
@@ -1,17 +1,33 @@
-use crate::{compiler::arch::riscv64::*, ir::VarID};
+use crate::{
+    compiler::arch::riscv64::*,
+    ir::{VarID, VarInst},
+};
 
 #[derive(Copy, Clone)]
 pub enum RV64Instruction {
     Ecall,
-    Li { dest: RegRef, imm: i64 },
-    Mv { dest: RegRef, src: RegRef },
-    La { dest: RegRef, src: VarID },
-    Ld { dest: RegRef, offset: i64, base: RegRef },
+    Li {
+        dest: RegRef,
+        imm: i64,
+    },
+    Mv {
+        dest: RegRef,
+        src: RegRef,
+    },
+    La {
+        dest: RegRef,
+        src: VarInst,
+    },
+    Ld {
+        dest: RegRef,
+        offset: i64,
+        base: RegRef,
+    },
 }
 
 #[derive(Copy, Clone)]
 pub enum RegRef {
-    Var(VarID),
+    Var(VarInst),
     Reg(Reg),
 }
 
diff --git a/src/ir/lower/program.rs b/src/ir/lower/program.rs
index 07f6ea1..06b6360 100644
--- a/src/ir/lower/program.rs
+++ b/src/ir/lower/program.rs
@@ -1,8 +1,8 @@
 use std::collections::HashMap;
 
-use crate::ir::{FnID, SymbolSpace};
+use crate::ir::SymbolSpace;
 
-use super::{IRLFunction, IRLInstruction, IRUInstruction, Len, Namespace, Symbol, VarID};
+use super::{IRLFunction, IRLInstruction, IRUInstruction, IRUProgram, Len, Symbol, Type, VarID};
 
 pub struct IRLProgram {
     sym_space: SymbolSpace,
@@ -12,110 +12,116 @@ pub struct IRLProgram {
 // NOTE: there are THREE places here where I specify size (8)
 
 impl IRLProgram {
-    pub fn create(ns: &Namespace) -> Option<Self> {
+    pub fn create(p: &IRUProgram) -> Result<Self, String> {
         let mut start = None;
-        for (i, f) in ns.iter_fns() {
-            if f?.name == "start" {
+        for (i, f) in p.iter_fns() {
+            if f.name == "start" {
                 start = Some(i);
             }
         }
-        let start = start?;
+        let start = start.ok_or("no start method found")?;
         let mut builder = SymbolSpace::with_entries(&[start]);
         let entry = builder.func(&start);
         while let Some((sym, i)) = builder.pop_fn() {
-            let f = ns.fns[i.0].as_ref().unwrap();
+            let f = p.fns[i.0].as_ref().unwrap();
             let mut instrs = Vec::new();
             let mut stack = HashMap::new();
             let mut makes_call = false;
-            let mut alloc_stack = |i: &VarID| -> bool {
+            let mut alloc_stack = |i: VarID| -> bool {
                 let size = *stack
-                    .entry(*i)
-                    .or_insert(ns.size_of_var(i).expect("unsized type"));
+                    .entry(i)
+                    .or_insert(p.size_of_var(i).expect("unsized type"));
                 size == 0
             };
             for i in &f.instructions {
-                match i {
+                match &i.i {
                     IRUInstruction::Mv { dest, src } => {
-                        if alloc_stack(dest) {
+                        if alloc_stack(dest.id) {
                             continue;
                         }
                         instrs.push(IRLInstruction::Mv {
-                            dest: *dest,
-                            src: *src,
+                            dest: dest.id,
+                            src: src.id,
                         });
                     }
                     IRUInstruction::Ref { dest, src } => {
-                        if alloc_stack(dest) {
+                        if alloc_stack(dest.id) {
                             continue;
                         }
                         instrs.push(IRLInstruction::Ref {
-                            dest: *dest,
-                            src: *src,
+                            dest: dest.id,
+                            src: src.id,
                         });
                     }
                     IRUInstruction::LoadData { dest, src } => {
-                        if alloc_stack(dest) {
+                        if alloc_stack(dest.id) {
                             continue;
                         }
-                        let data = &ns.data[src.0];
+                        let data = &p.data[src.0];
                         let sym = builder.ro_data(src, data);
                         instrs.push(IRLInstruction::LoadData {
-                            dest: *dest,
+                            dest: dest.id,
                             offset: 0,
                             len: data.len() as Len,
                             src: sym,
                         });
                     }
-                    IRUInstruction::LoadSlice { dest, src, len } => {
-                        if alloc_stack(dest) {
+                    IRUInstruction::LoadSlice { dest, src } => {
+                        if alloc_stack(dest.id) {
                             continue;
                         }
-                        let sym = builder.ro_data(src, &ns.data[src.0]);
+                        let data = &p.data[src.0];
+                        let def = p.get_data(*src);
+                        let Type::Array(ty, len) = &def.ty else {
+                            return Err(format!("tried to load {} as slice", p.type_name(&def.ty)));
+                        };
+                        let sym = builder.ro_data(src, data);
                         instrs.push(IRLInstruction::LoadAddr {
-                            dest: *dest,
+                            dest: dest.id,
                             offset: 0,
                             src: sym,
                         });
+
                         let sym = builder.anon_ro_data(&(*len as u64).to_le_bytes());
                         instrs.push(IRLInstruction::LoadData {
-                            dest: *dest,
+                            dest: dest.id,
                             offset: 8,
                             len: 8,
                             src: sym,
                         });
                     }
                     IRUInstruction::LoadFn { dest, src } => {
-                        if alloc_stack(dest) {
+                        if alloc_stack(dest.id) {
                             continue;
                         }
                         let sym = builder.func(src);
                         instrs.push(IRLInstruction::LoadAddr {
-                            dest: *dest,
+                            dest: dest.id,
                             offset: 0,
                             src: sym,
                         });
                     }
                     IRUInstruction::Call { dest, f, args } => {
-                        alloc_stack(dest);
+                        alloc_stack(dest.id);
                         makes_call = true;
-                        let fid = &ns.fn_map[f];
+                        let fid = &p.fn_map[&f.id];
                         let sym = builder.func(fid);
                         instrs.push(IRLInstruction::Call {
-                            dest: *dest,
+                            dest: dest.id,
                             f: sym,
                             args: args
                                 .iter()
-                                .map(|a| (*a, ns.size_of_var(a).expect("unsized type")))
+                                .map(|a| (a.id, p.size_of_var(a.id).expect("unsized type")))
                                 .collect(),
                         });
                     }
                     IRUInstruction::AsmBlock { instructions, args } => {
                         instrs.push(IRLInstruction::AsmBlock {
                             instructions: instructions.clone(),
-                            args: args.clone(),
+                            args: args.iter().cloned().map(|(r, v)| (r, v.id)).collect(),
                         })
                     }
-                    IRUInstruction::Ret { src } => instrs.push(IRLInstruction::Ret { src: *src }),
+                    IRUInstruction::Ret { src } => instrs.push(IRLInstruction::Ret { src: src.id }),
                 };
             }
             builder.write_fn(
@@ -127,7 +133,7 @@ impl IRLProgram {
                     args: f
                         .args
                         .iter()
-                        .map(|a| (*a, ns.size_of_var(a).expect("unsized type")))
+                        .map(|a| (*a, p.size_of_var(*a).expect("unsized type")))
                         .collect(),
                     stack,
                 },
@@ -139,7 +145,7 @@ impl IRLProgram {
         //     println!("    {:?}: {}", a, f.name);
         // }
         // println!("datas: {}", sym_space.ro_data().len());
-        Some(Self { sym_space, entry })
+        Ok(Self { sym_space, entry })
     }
 
     pub fn entry(&self) -> Symbol {
diff --git a/src/ir/mod.rs b/src/ir/mod.rs
index 68ff9eb..2883df1 100644
--- a/src/ir/mod.rs
+++ b/src/ir/mod.rs
@@ -1,5 +1,4 @@
 mod upper;
-mod file;
 mod lower;
 mod id;
 mod asm;
@@ -7,5 +6,4 @@ pub mod arch;
 
 pub use upper::*;
 pub use lower::*;
-pub use file::*;
 pub use id::*;
diff --git a/src/ir/upper/def.rs b/src/ir/upper/def.rs
index da5f9af..97c4314 100644
--- a/src/ir/upper/def.rs
+++ b/src/ir/upper/def.rs
@@ -1,4 +1,6 @@
-use super::{FileSpan, Type};
+use crate::common::FileSpan;
+
+use super::Type;
 use std::fmt::Debug;
 
 #[derive(Clone)]
@@ -23,6 +25,12 @@ pub struct VarDef {
     pub origin: Origin,
 }
 
+#[derive(Clone)]
+pub struct DataDef {
+    pub ty: Type,
+    pub origin: Origin,
+}
+
 #[derive(Debug, Clone, Copy)]
 pub enum Origin {
     Builtin,
diff --git a/src/ir/upper/error.rs b/src/ir/upper/error.rs
new file mode 100644
index 0000000..f2ffe52
--- /dev/null
+++ b/src/ir/upper/error.rs
@@ -0,0 +1,19 @@
+use crate::common::{CompilerMsg, CompilerOutput, FileSpan};
+
+use super::{IRUProgram, Type};
+
+impl CompilerOutput {
+    pub fn check_assign(&mut self, p: &IRUProgram, src: &Type, dest: &Type, span: FileSpan) {
+        // TODO: spans
+        if src != dest {
+            self.err(CompilerMsg {
+                msg: format!(
+                    "Cannot assign type '{}' to '{}'",
+                    p.type_name(src),
+                    p.type_name(dest)
+                ),
+                spans: vec![span],
+            });
+        }
+    }
+}
diff --git a/src/ir/upper/func.rs b/src/ir/upper/func.rs
index d9c190e..f5fdbe5 100644
--- a/src/ir/upper/func.rs
+++ b/src/ir/upper/func.rs
@@ -1,52 +1,51 @@
 use std::fmt::Write;
 
-use super::{arch::riscv64::RV64Instruction, DataID, FnID, Len, VarID};
-use crate::{compiler::arch::riscv64::Reg, util::Padder};
+use super::{arch::riscv64::RV64Instruction, inst::VarInst, DataID, FnID, IRUInstrInst, VarID};
+use crate::{common::FileSpan, compiler::arch::riscv64::Reg, util::Padder};
 
 pub struct IRUFunction {
     pub name: String,
     pub args: Vec<VarID>,
-    pub instructions: Vec<IRUInstruction>,
+    pub instructions: Vec<IRUInstrInst>,
 }
 
 pub enum IRUInstruction {
     Mv {
-        dest: VarID,
-        src: VarID,
+        dest: VarInst,
+        src: VarInst,
     },
     Ref {
-        dest: VarID,
-        src: VarID,
+        dest: VarInst,
+        src: VarInst,
     },
     LoadData {
-        dest: VarID,
+        dest: VarInst,
         src: DataID,
     },
     LoadSlice {
-        dest: VarID,
+        dest: VarInst,
         src: DataID,
-        len: Len,
     },
     LoadFn {
-        dest: VarID,
+        dest: VarInst,
         src: FnID,
     },
     Call {
-        dest: VarID,
-        f: VarID,
-        args: Vec<VarID>,
+        dest: VarInst,
+        f: VarInst,
+        args: Vec<VarInst>,
     },
     AsmBlock {
         instructions: Vec<RV64Instruction>,
-        args: Vec<(Reg, VarID)>,
+        args: Vec<(Reg, VarInst)>,
     },
     Ret {
-        src: VarID,
+        src: VarInst,
     },
 }
 
 pub struct IRInstructions {
-    vec: Vec<IRUInstruction>,
+    vec: Vec<IRUInstrInst>,
 }
 
 impl IRUFunction {
@@ -63,8 +62,8 @@ impl IRInstructions {
     pub fn new() -> Self {
         Self { vec: Vec::new() }
     }
-    pub fn push(&mut self, i: IRUInstruction) {
-        self.vec.push(i);
+    pub fn push(&mut self, i: IRUInstruction, span: FileSpan) {
+        self.vec.push(IRUInstrInst { i, span });
     }
 }
 
@@ -75,7 +74,7 @@ impl std::fmt::Debug for IRUInstruction {
             Self::Ref { dest, src } => write!(f, "{dest:?} <- &{src:?}"),
             Self::LoadData { dest, src } => write!(f, "{dest:?} <- {src:?}"),
             Self::LoadFn { dest, src } => write!(f, "{dest:?} <- {src:?}"),
-            Self::LoadSlice { dest, src, len } => write!(f, "{dest:?} <- &[{src:?}; {len}]"),
+            Self::LoadSlice { dest, src } => write!(f, "{dest:?} <- &[{src:?}]"),
             Self::Call {
                 dest,
                 f: func,
diff --git a/src/ir/upper/inst.rs b/src/ir/upper/inst.rs
new file mode 100644
index 0000000..6e93092
--- /dev/null
+++ b/src/ir/upper/inst.rs
@@ -0,0 +1,27 @@
+use crate::{common::FileSpan, ir::VarID};
+use std::fmt::Debug;
+
+use super::IRUInstruction;
+
+#[derive(Clone, Copy)]
+pub struct VarInst {
+    pub id: VarID,
+    pub span: FileSpan,
+}
+
+pub struct IRUInstrInst {
+    pub i: IRUInstruction,
+    pub span: FileSpan,
+}
+
+impl Debug for VarInst {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{:?}", self.id)
+    }
+}
+
+impl Debug for IRUInstrInst {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "{:?}", self.i)
+    }
+}
diff --git a/src/ir/upper/mod.rs b/src/ir/upper/mod.rs
index c027275..56992f9 100644
--- a/src/ir/upper/mod.rs
+++ b/src/ir/upper/mod.rs
@@ -1,10 +1,14 @@
 mod def;
 mod func;
 mod ty;
-mod namespace;
+mod program;
+mod validate;
+mod error;
+mod inst;
 
 use super::*;
 pub use def::*;
 pub use func::*;
 pub use ty::*;
-pub use namespace::*;
+pub use program::*;
+pub use inst::*;
diff --git a/src/ir/upper/namespace.rs b/src/ir/upper/program.rs
similarity index 88%
rename from src/ir/upper/namespace.rs
rename to src/ir/upper/program.rs
index f296390..ebf232d 100644
--- a/src/ir/upper/namespace.rs
+++ b/src/ir/upper/program.rs
@@ -4,12 +4,15 @@ use std::{
     ops::{Deref, DerefMut},
 };
 
-use super::*;
+use crate::common::FileSpan;
 
-pub struct Namespace {
+use super::{inst::VarInst, *};
+
+pub struct IRUProgram {
     pub fn_defs: Vec<FnDef>,
     pub var_defs: Vec<VarDef>,
     pub type_defs: Vec<TypeDef>,
+    pub data_defs: Vec<DataDef>,
     pub fns: Vec<Option<IRUFunction>>,
     pub data: Vec<Vec<u8>>,
     pub fn_map: HashMap<VarID, FnID>,
@@ -17,12 +20,13 @@ pub struct Namespace {
     pub stack: Vec<HashMap<String, Idents>>,
 }
 
-impl Namespace {
+impl IRUProgram {
     pub fn new() -> Self {
         Self {
             fn_defs: Vec::new(),
             var_defs: Vec::new(),
             type_defs: Vec::new(),
+            data_defs: Vec::new(),
             data: Vec::new(),
             fn_map: HashMap::new(),
             fns: Vec::new(),
@@ -49,6 +53,9 @@ impl Namespace {
     pub fn get_fn(&self, id: FnID) -> &FnDef {
         &self.fn_defs[id.0]
     }
+    pub fn get_data(&self, id: DataID) -> &DataDef {
+        &self.data_defs[id.0]
+    }
     pub fn get_fn_var(&self, id: VarID) -> Option<&FnDef> {
         Some(&self.fn_defs[self.fn_map.get(&id)?.0])
     }
@@ -90,17 +97,20 @@ impl Namespace {
             Type::Unit => 0,
         })
     }
-    pub fn size_of_var(&self, var: &VarID) -> Option<Size> {
+    pub fn size_of_var(&self, var: VarID) -> Option<Size> {
         self.size_of_type(&self.var_defs[var.0].ty)
     }
-    pub fn temp_var(&mut self, origin: FileSpan, ty: Type) -> VarID {
+    pub fn temp_var(&mut self, origin: FileSpan, ty: Type) -> VarInst {
         let v = self.def_var(VarDef {
             name: format!("temp{}", self.temp),
             origin: super::Origin::File(origin),
             ty,
         });
         self.temp += 1;
-        v
+        VarInst {
+            id: v,
+            span: origin,
+        }
     }
     pub fn def_fn(&mut self, def: FnDef) -> FnID {
         let i = self.fn_defs.len();
@@ -128,8 +138,9 @@ impl Namespace {
         self.type_defs.push(def);
         id
     }
-    pub fn def_data(&mut self, bytes: Vec<u8>) -> DataID {
+    pub fn def_data(&mut self, def: DataDef, bytes: Vec<u8>) -> DataID {
         let i = self.data.len();
+        self.data_defs.push(def);
         self.data.push(bytes);
         DataID(i)
     }
@@ -187,18 +198,17 @@ impl Namespace {
         self.fns[id.0] = Some(f);
     }
     pub fn iter_vars(&self) -> impl Iterator<Item = (VarID, &VarDef)> {
-        (0..self.var_defs.len())
-            .map(|i| VarID(i))
-            .zip(self.var_defs.iter())
+        self.var_defs.iter().enumerate().map(|(i, v)| (VarID(i), v))
     }
-    pub fn iter_fns(&self) -> impl Iterator<Item = (FnID, Option<&IRUFunction>)> {
-        (0..self.fns.len())
-            .map(|i| FnID(i))
-            .zip(self.fns.iter().map(|f| f.as_ref()))
+    pub fn iter_fns(&self) -> impl Iterator<Item = (FnID, &IRUFunction)> {
+        self.fns
+            .iter()
+            .enumerate()
+            .flat_map(|(i, f)| Some((FnID(i), f.as_ref()?)))
     }
 }
 
-pub struct NamespaceGuard<'a>(&'a mut Namespace);
+pub struct NamespaceGuard<'a>(&'a mut IRUProgram);
 
 impl Drop for NamespaceGuard<'_> {
     fn drop(&mut self) {
@@ -207,7 +217,7 @@ impl Drop for NamespaceGuard<'_> {
 }
 
 impl Deref for NamespaceGuard<'_> {
-    type Target = Namespace;
+    type Target = IRUProgram;
     fn deref(&self) -> &Self::Target {
         self.0
     }
diff --git a/src/ir/upper/ty.rs b/src/ir/upper/ty.rs
index 89ac718..3f3cb6e 100644
--- a/src/ir/upper/ty.rs
+++ b/src/ir/upper/ty.rs
@@ -1,6 +1,6 @@
-use super::{Len, TypeID};
+use super::{IRUInstruction, IRUProgram, Len, TypeID};
 
-#[derive(Clone)]
+#[derive(Clone, PartialEq)]
 pub enum Type {
     Concrete(TypeID),
     Bits(u32),
@@ -25,3 +25,20 @@ impl Type {
         Self::Slice(Box::new(self))
     }
 }
+
+pub fn resolve_types(ns: &IRUProgram) {
+    for (i, f) in ns.iter_fns() {
+        for inst in &f.instructions {
+            match &inst.i {
+                IRUInstruction::Mv { dest, src } => todo!(),
+                IRUInstruction::Ref { dest, src } => todo!(),
+                IRUInstruction::LoadData { dest, src } => todo!(),
+                IRUInstruction::LoadSlice { dest, src } => todo!(),
+                IRUInstruction::LoadFn { dest, src } => todo!(),
+                IRUInstruction::Call { dest, f, args } => todo!(),
+                IRUInstruction::AsmBlock { instructions, args } => todo!(),
+                IRUInstruction::Ret { src } => todo!(),
+            }
+        }
+    }
+}
diff --git a/src/ir/upper/validate.rs b/src/ir/upper/validate.rs
new file mode 100644
index 0000000..407ee6a
--- /dev/null
+++ b/src/ir/upper/validate.rs
@@ -0,0 +1,52 @@
+// TODO: move this into ir, not parser
+use super::{IRUProgram, Type};
+use crate::common::CompilerOutput;
+
+impl IRUProgram {
+    pub fn validate(&self) -> CompilerOutput {
+        let mut output = CompilerOutput::new();
+        for f in self.fns.iter().flatten() {
+            for i in &f.instructions {
+                match &i.i {
+                    super::IRUInstruction::Mv { dest, src } => {
+                        let dest = self.get_var(dest.id);
+                        let src = self.get_var(src.id);
+                        output.check_assign(self, &src.ty, &dest.ty, i.span);
+                    }
+                    super::IRUInstruction::Ref { dest, src } => todo!(),
+                    super::IRUInstruction::LoadData { dest, src } => {
+                        let dest = self.get_var(dest.id);
+                        let src = self.get_data(*src);
+                        output.check_assign(self, &src.ty, &dest.ty, i.span);
+                    }
+                    super::IRUInstruction::LoadSlice { dest, src } => {
+                        let dest = self.get_var(dest.id);
+                        let src = self.get_data(*src);
+                        let Type::Array(srcty, ..) = &src.ty else {
+                            todo!()
+                        };
+                        output.check_assign(self, &Type::Slice(srcty.clone()), &dest.ty, i.span);
+                    }
+                    super::IRUInstruction::LoadFn { dest, src } => todo!(),
+                    super::IRUInstruction::Call { dest, f, args } => {
+                        let destty = &self.get_var(dest.id).ty;
+                        let f = self.get_var(f.id);
+                        let Type::Fn { args: argtys, ret } = &f.ty else {
+                            todo!()
+                        };
+                        output.check_assign(self, ret, destty, dest.span);
+                        for (argv, argt) in args.iter().zip(argtys) {
+                            let dest = self.get_var(argv.id);
+                            output.check_assign(self, argt, &dest.ty, argv.span);
+                        }
+                    }
+                    super::IRUInstruction::AsmBlock { instructions, args } => {
+                        // TODO
+                    }
+                    super::IRUInstruction::Ret { src } => todo!(),
+                }
+            }
+        }
+        output
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index abdcebb..9cc250f 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,7 +1,7 @@
 #![feature(box_patterns)]
 #![feature(try_trait_v2)]
 
-use ir::{Namespace, IRLProgram};
+use ir::{IRLProgram, IRUProgram};
 use parser::{NodeParsable, PModule, PStatement, ParserCtx};
 use std::{
     fs::{create_dir_all, OpenOptions},
@@ -11,10 +11,12 @@ use std::{
     process::Command,
 };
 
+mod common;
 mod compiler;
 mod ir;
 mod parser;
 mod util;
+use common::*;
 
 fn main() {
     let file = std::env::args_os().nth(1);
@@ -34,7 +36,7 @@ fn run_file(file: &str, gdb: bool) {
         // println!("Parsed:");
         // println!("{:#?}", res.node);
         if let Some(module) = res.node.as_ref() {
-            let mut namespace = Namespace::new();
+            let mut namespace = IRUProgram::new();
             module.lower(&mut namespace.push(), &mut ctx.output);
             if ctx.output.errs.is_empty() {
                 // println!("vars:");
@@ -44,10 +46,14 @@ fn run_file(file: &str, gdb: bool) {
                 // for (id, f) in namespace.iter_fns() {
                 //     println!("{id:?} = {:#?}", f.unwrap());
                 // }
-                let program = IRLProgram::create(&namespace);
-                let bin = compiler::compile(program.expect("morir"));
-                println!("compiled");
-                save_run(&bin, gdb);
+                let output = namespace.validate();
+                output.write_for(&mut stdout(), file);
+                if output.errs.is_empty() {
+                    let program = IRLProgram::create(&namespace);
+                    let bin = compiler::compile(program.expect("morir"));
+                    println!("compiled");
+                    save_run(&bin, gdb);
+                }
             }
         }
     }
diff --git a/src/parser/v3/ctx.rs b/src/parser/v3/ctx.rs
index 93c8705..0b31515 100644
--- a/src/parser/v3/ctx.rs
+++ b/src/parser/v3/ctx.rs
@@ -1,10 +1,13 @@
 use std::ops::{Deref, DerefMut};
 
-use super::{MaybeParsable, Node, NodeParseResult, Parsable, ParserMsg, ParserOutput, TokenCursor};
+use super::{
+    MaybeParsable, Node, NodeParseResult, Parsable, ParsableWith, CompilerMsg, CompilerOutput,
+    TokenCursor,
+};
 
 pub struct ParserCtx<'a> {
     pub cursor: TokenCursor<'a>,
-    pub output: ParserOutput,
+    pub output: CompilerOutput,
 }
 
 impl<'a> Deref for ParserCtx<'a> {
@@ -22,15 +25,18 @@ impl DerefMut for ParserCtx<'_> {
 }
 
 impl<'a> ParserCtx<'a> {
-    pub fn err(&mut self, msg: ParserMsg) {
+    pub fn err(&mut self, msg: CompilerMsg) {
         self.output.err(msg);
     }
-    pub fn hint(&mut self, msg: ParserMsg) {
+    pub fn hint(&mut self, msg: CompilerMsg) {
         self.output.hint(msg);
     }
     pub fn parse<T: Parsable>(&mut self) -> NodeParseResult<T> {
         Node::parse(self)
     }
+    pub fn parse_with<T: ParsableWith>(&mut self, data: T::Data) -> NodeParseResult<T> {
+        Node::parse_with(self, data)
+    }
     pub fn maybe_parse<T: MaybeParsable>(&mut self) -> Option<Node<T>> {
         Node::maybe_parse(self)
     }
@@ -40,7 +46,7 @@ impl<'a> From<TokenCursor<'a>> for ParserCtx<'a> {
     fn from(cursor: TokenCursor<'a>) -> Self {
         Self {
             cursor,
-            output: ParserOutput::new(),
+            output: CompilerOutput::new(),
         }
     }
 }
@@ -49,7 +55,7 @@ impl<'a> From<&'a str> for ParserCtx<'a> {
     fn from(string: &'a str) -> Self {
         Self {
             cursor: TokenCursor::from(string),
-            output: ParserOutput::new(),
+            output: CompilerOutput::new(),
         }
     }
 }
diff --git a/src/parser/v3/cursor.rs b/src/parser/v3/cursor.rs
index ae430b0..3cabf9e 100644
--- a/src/parser/v3/cursor.rs
+++ b/src/parser/v3/cursor.rs
@@ -1,7 +1,7 @@
-use crate::ir::FilePos;
-
-use super::error::ParserMsg;
-use super::token::{CharCursor, Keyword, Symbol, Token, TokenInstance};
+use super::{
+    token::{CharCursor, Keyword, Symbol, Token, TokenInstance},
+    CompilerMsg, FilePos,
+};
 
 pub struct TokenCursor<'a> {
     cursor: CharCursor<'a>,
@@ -12,11 +12,7 @@ pub struct TokenCursor<'a> {
 
 impl<'a> TokenCursor<'a> {
     pub fn next(&mut self) -> Option<TokenInstance> {
-        self.prev_end = self
-            .next
-            .as_ref()
-            .map(|i| i.span.end)
-            .unwrap_or(FilePos::start());
+        self.prev_end = self.cursor.prev_pos();
         let next = TokenInstance::parse(&mut self.cursor);
         self.next_start = next
             .as_ref()
@@ -24,19 +20,19 @@ impl<'a> TokenCursor<'a> {
             .unwrap_or(FilePos::start());
         std::mem::replace(&mut self.next, next)
     }
-    pub fn expect_next(&mut self) -> Result<TokenInstance, ParserMsg> {
-        self.peek().ok_or(ParserMsg::unexpected_end())?;
+    pub fn expect_next(&mut self) -> Result<TokenInstance, CompilerMsg> {
+        self.peek().ok_or(CompilerMsg::unexpected_end())?;
         Ok(self.next().unwrap())
     }
-    pub fn expect_token(&mut self, t: Token) -> Result<(), ParserMsg> {
+    pub fn expect_token(&mut self, t: Token) -> Result<(), CompilerMsg> {
         let next = self.expect_next()?;
         if t == next.token {
             Ok(())
         } else {
-            Err(ParserMsg::unexpected_token(&next, &format!("{t:?}")))
+            Err(CompilerMsg::unexpected_token(&next, &format!("{t:?}")))
         }
     }
-    pub fn expect_sym(&mut self, symbol: Symbol) -> Result<(), ParserMsg> {
+    pub fn expect_sym(&mut self, symbol: Symbol) -> Result<(), CompilerMsg> {
         self.expect_token(Token::Symbol(symbol))
     }
     pub fn next_on_new_line(&mut self) -> bool {
@@ -64,14 +60,14 @@ impl<'a> TokenCursor<'a> {
             self.next();
         }
     }
-    pub fn expect_kw(&mut self, kw: Keyword) -> Result<(), ParserMsg> {
+    pub fn expect_kw(&mut self, kw: Keyword) -> Result<(), CompilerMsg> {
         self.expect_token(Token::Keyword(kw))
     }
     pub fn peek(&self) -> Option<&TokenInstance> {
         self.next.as_ref()
     }
-    pub fn expect_peek(&mut self) -> Result<&TokenInstance, ParserMsg> {
-        self.peek().ok_or(ParserMsg::unexpected_end())
+    pub fn expect_peek(&mut self) -> Result<&TokenInstance, CompilerMsg> {
+        self.peek().ok_or(CompilerMsg::unexpected_end())
     }
     pub fn chars(&mut self) -> &mut CharCursor<'a> {
         &mut self.cursor
diff --git a/src/parser/v3/error.rs b/src/parser/v3/error.rs
index db1ebe7..b707240 100644
--- a/src/parser/v3/error.rs
+++ b/src/parser/v3/error.rs
@@ -1,36 +1,17 @@
-use crate::ir::{FilePos, FileSpan};
+use super::Node;
+use super::PIdent;
+use super::CompilerMsg;
+use super::TokenInstance;
 
-use super::{token::TokenInstance, PIdent, Node};
-
-#[derive(Debug, Clone)]
-pub struct ParserMsg {
-    pub msg: String,
-    pub spans: Vec<FileSpan>,
-}
-
-pub struct ParserOutput {
-    pub errs: Vec<ParserMsg>,
-    pub hints: Vec<ParserMsg>,
-}
-
-impl ParserMsg {
+impl CompilerMsg {
     pub fn from_instances(instances: &[&TokenInstance], msg: String) -> Self {
-        ParserMsg {
+        CompilerMsg {
             msg,
             spans: instances.iter().map(|i| i.span).collect(),
         }
     }
-    pub fn from_msg(msg: String) -> Self {
-        Self {
-            msg,
-            spans: Vec::new(),
-        }
-    }
-    pub fn from_span(span: FileSpan, msg: String) -> Self {
-        Self {
-            msg,
-            spans: vec![span],
-        }
+    pub fn unexpected_end() -> Self {
+        Self::from_msg("unexpected end of input".to_string())
     }
     pub fn identifier_not_found(id: &Node<PIdent>) -> Self {
         Self {
@@ -38,51 +19,11 @@ impl ParserMsg {
             spans: vec![id.span],
         }
     }
-    pub fn at(pos: FilePos, msg: String) -> Self {
-        Self {
-            msg,
-            spans: vec![FileSpan::at(pos)],
-        }
-    }
-    pub fn unexpected_end() -> Self {
-        Self::from_msg("unexpected end of input".to_string())
-    }
     pub fn unexpected_token(inst: &TokenInstance, expected: &str) -> Self {
         let t = &inst.token;
-        ParserMsg::from_instances(
+        CompilerMsg::from_instances(
             &[inst],
             format!("unexpected token {t:?}; expected {expected}"),
         )
     }
-    pub fn write_for(&self, ty: &str, writer: &mut impl std::io::Write, file: &str) -> std::io::Result<()> {
-        let after = if self.spans.is_empty() { "" } else { ":" };
-        writeln!(writer, "{}: {}{}", ty, self.msg, after)?;
-        for span in &self.spans {
-            span.write_for(writer, file)?;
-        }
-        Ok(())
-    }
-}
-
-impl ParserOutput {
-    pub fn new() -> Self {
-        Self {
-            errs: Vec::new(),
-            hints: Vec::new(),
-        }
-    }
-    pub fn err(&mut self, msg: ParserMsg) {
-        self.errs.push(msg);
-    }
-    pub fn hint(&mut self, msg: ParserMsg) {
-        self.hints.push(msg);
-    }
-    pub fn write_for(&self, out: &mut impl std::io::Write, file: &str) {
-        for err in &self.errs {
-            err.write_for("error", out, file).unwrap();
-        }
-        for hint in &self.hints {
-            hint.write_for("hint", out, file).unwrap();
-        }
-    }
 }
diff --git a/src/parser/v3/lower/arch/riscv64.rs b/src/parser/v3/lower/arch/riscv64.rs
index 79cb72d..eb2cc92 100644
--- a/src/parser/v3/lower/arch/riscv64.rs
+++ b/src/parser/v3/lower/arch/riscv64.rs
@@ -3,7 +3,7 @@ use crate::{
     compiler::arch::riscv64::*,
     ir::{
         arch::riscv64::{RV64Instruction, RegRef},
-        VarID,
+        VarInst,
     },
 };
 
@@ -57,7 +57,7 @@ impl RV64Instruction {
     }
 }
 
-pub fn arg_to_var(node: &Node<PAsmArg>, ctx: &mut FnLowerCtx) -> Option<VarID> {
+pub fn arg_to_var(node: &Node<PAsmArg>, ctx: &mut FnLowerCtx) -> Option<VarInst> {
     let PAsmArg::Ref(node) = node.inner.as_ref()? else {
         ctx.err_at(
             node.span,
diff --git a/src/parser/v3/lower/asm.rs b/src/parser/v3/lower/asm.rs
index b8dfd46..b65aeb8 100644
--- a/src/parser/v3/lower/asm.rs
+++ b/src/parser/v3/lower/asm.rs
@@ -1,9 +1,9 @@
 use crate::{
     compiler::arch::riscv64::Reg,
-    ir::{arch::riscv64::RV64Instruction, IRUInstruction, VarID},
+    ir::{arch::riscv64::RV64Instruction, IRUInstruction, VarInst},
 };
 
-use super::{PAsmBlock, PAsmBlockArg, FnLowerCtx, FnLowerable, PInstruction};
+use super::{FnLowerCtx, FnLowerable, PAsmBlock, PAsmBlockArg, PInstruction};
 
 impl FnLowerable for PInstruction {
     type Output = RV64Instruction;
@@ -43,7 +43,7 @@ impl FnLowerable for PAsmBlock {
 }
 
 impl FnLowerable for PAsmBlockArg {
-    type Output = (Reg, VarID);
+    type Output = (Reg, VarInst);
 
     fn lower(&self, ctx: &mut FnLowerCtx) -> Option<Self::Output> {
         let var = ctx.get_var(&self.var)?;
diff --git a/src/parser/v3/lower/block.rs b/src/parser/v3/lower/block.rs
index 39ed048..b735f91 100644
--- a/src/parser/v3/lower/block.rs
+++ b/src/parser/v3/lower/block.rs
@@ -1,10 +1,10 @@
-use crate::ir::{IRUInstruction, VarID};
+use crate::ir::{IRUInstruction, VarInst};
 
-use super::{PBlock, FnLowerCtx, FnLowerable, PStatement};
+use super::{FnLowerCtx, FnLowerable, PBlock, PStatement};
 
 impl FnLowerable for PBlock {
-    type Output = VarID;
-    fn lower(&self, ctx: &mut FnLowerCtx) -> Option<VarID> {
+    type Output = VarInst;
+    fn lower(&self, ctx: &mut FnLowerCtx) -> Option<VarInst> {
         let ctx = &mut ctx.sub();
         for statement in &self.statements {
             statement.lower(ctx);
@@ -14,20 +14,20 @@ impl FnLowerable for PBlock {
 }
 
 impl FnLowerable for PStatement {
-    type Output = VarID;
-    fn lower(&self, ctx: &mut FnLowerCtx) -> Option<VarID> {
+    type Output = VarInst;
+    fn lower(&self, ctx: &mut FnLowerCtx) -> Option<VarInst> {
         match self {
             super::PStatement::Let(def, e) => {
                 let def = def.lower(ctx.map, ctx.output)?;
                 let res = e.lower(ctx);
                 if let Some(res) = res {
-                    ctx.map.name_var(&def, res);
+                    ctx.map.name_var(&def, res.id);
                 }
                 None
             }
             super::PStatement::Return(e) => {
                 let src = e.lower(ctx)?;
-                ctx.push(IRUInstruction::Ret { src });
+                ctx.push_at(IRUInstruction::Ret { src }, src.span);
                 None
             }
             super::PStatement::Expr(e) => e.lower(ctx),
diff --git a/src/parser/v3/lower/def.rs b/src/parser/v3/lower/def.rs
index 0e4a3ef..2b8a9cc 100644
--- a/src/parser/v3/lower/def.rs
+++ b/src/parser/v3/lower/def.rs
@@ -1,12 +1,12 @@
-use crate::ir::{FileSpan, NamespaceGuard, Origin, Type, VarDef};
+use crate::ir::{NamespaceGuard, Origin, Type, VarDef};
 
-use super::{Node, PType, PVarDef, ParserMsg, ParserOutput};
+use super::{CompilerMsg, CompilerOutput, FileSpan, Node, PType, PVarDef};
 
 impl Node<PVarDef> {
     pub fn lower(
         &self,
         namespace: &mut NamespaceGuard,
-        output: &mut ParserOutput,
+        output: &mut CompilerOutput,
     ) -> Option<VarDef> {
         let s = self.as_ref()?;
         let name = s.name.as_ref()?.to_string();
@@ -23,7 +23,7 @@ impl Node<PVarDef> {
 }
 
 impl Node<PType> {
-    pub fn lower(&self, namespace: &mut NamespaceGuard, output: &mut ParserOutput) -> Type {
+    pub fn lower(&self, namespace: &mut NamespaceGuard, output: &mut CompilerOutput) -> Type {
         self.as_ref()
             .map(|t| t.lower(namespace, output, self.span))
             .unwrap_or(Type::Error)
@@ -34,7 +34,7 @@ impl PType {
     pub fn lower(
         &self,
         namespace: &mut NamespaceGuard,
-        output: &mut ParserOutput,
+        output: &mut CompilerOutput,
         span: FileSpan,
     ) -> Type {
         match namespace.get(&self.name).and_then(|ids| ids.ty) {
@@ -60,7 +60,7 @@ impl PType {
                             Type::Slice(Box::new(inner))
                         }
                         _ => {
-                            output.err(ParserMsg::from_span(span, "Type not found".to_string()));
+                            output.err(CompilerMsg::from_span(span, "Type not found".to_string()));
                             Type::Error
                         }
                     }
diff --git a/src/parser/v3/lower/expr.rs b/src/parser/v3/lower/expr.rs
index 8f238dd..f2adb23 100644
--- a/src/parser/v3/lower/expr.rs
+++ b/src/parser/v3/lower/expr.rs
@@ -1,31 +1,48 @@
 use super::{func::FnLowerCtx, FnLowerable, PExpr, UnaryOp};
-use crate::ir::{IRUInstruction, Size, Type, VarID};
+use crate::ir::{DataDef, IRUInstruction, Origin, Type, VarInst};
 
 impl FnLowerable for PExpr {
-    type Output = VarID;
-    fn lower(&self, ctx: &mut FnLowerCtx) -> Option<VarID> {
+    type Output = VarInst;
+    fn lower(&self, ctx: &mut FnLowerCtx) -> Option<VarInst> {
         Some(match self {
             PExpr::Lit(l) => match l.as_ref()? {
                 super::PLiteral::String(s) => {
                     let dest = ctx.map.temp_var(l.span, Type::Bits(8).slice());
                     let data = s.as_bytes().to_vec();
-                    let len = data.len() as Size;
-                    let src = ctx.map.def_data(data);
-                    ctx.push(IRUInstruction::LoadSlice { dest, src, len });
+                    let src = ctx.map.def_data(
+                        DataDef {
+                            ty: Type::Bits(8).arr(data.len() as u32),
+                            origin: Origin::File(l.span),
+                        },
+                        data,
+                    );
+                    ctx.push(IRUInstruction::LoadSlice { dest, src });
                     dest
                 }
                 super::PLiteral::Char(c) => {
-                    let dest = ctx.map.temp_var(l.span, Type::Bits(8).slice());
-                    let src = ctx.map.def_data(c.to_string().as_bytes().to_vec());
+                    let ty = Type::Bits(8);
+                    let dest = ctx.map.temp_var(l.span, ty.clone());
+                    let src = ctx.map.def_data(
+                        DataDef {
+                            ty,
+                            origin: Origin::File(l.span),
+                        },
+                        c.to_string().as_bytes().to_vec(),
+                    );
                     ctx.push(IRUInstruction::LoadData { dest, src });
                     dest
                 }
                 super::PLiteral::Number(n) => {
                     // TODO: temp
+                    let ty = Type::Bits(64);
                     let dest = ctx.map.temp_var(l.span, Type::Bits(64));
-                    let src = ctx
-                        .map
-                        .def_data(n.whole.parse::<i64>().unwrap().to_le_bytes().to_vec());
+                    let src = ctx.map.def_data(
+                        DataDef {
+                            ty,
+                            origin: Origin::File(l.span),
+                        },
+                        n.whole.parse::<i64>().unwrap().to_le_bytes().to_vec(),
+                    );
                     ctx.push(IRUInstruction::LoadData { dest, src });
                     dest
                 }
@@ -44,7 +61,7 @@ impl FnLowerable for PExpr {
                 let res = e.lower(ctx)?;
                 match op {
                     UnaryOp::Ref => {
-                        let temp = ctx.temp(ctx.map.get_var(res).ty.clone());
+                        let temp = ctx.temp(ctx.map.get_var(res.id).ty.clone());
                         ctx.push(IRUInstruction::Ref {
                             dest: temp,
                             src: res,
@@ -52,7 +69,7 @@ impl FnLowerable for PExpr {
                         temp
                     }
                     UnaryOp::Deref => {
-                        let t = &ctx.map.get_var(res).ty;
+                        let t = &ctx.map.get_var(res.id).ty;
                         let Type::Ref(inner) = t else {
                             ctx.err(format!(
                                 "Cannot dereference type {:?}",
@@ -77,7 +94,7 @@ impl FnLowerable for PExpr {
                     let arg = arg.lower(ctx)?;
                     nargs.push(arg);
                 }
-                let def = ctx.map.get_fn_var(fe);
+                let def = ctx.map.get_fn_var(fe.id);
                 let ty = match def {
                     Some(def) => def.ret.clone(),
                     None => {
@@ -85,7 +102,7 @@ impl FnLowerable for PExpr {
                             e.span,
                             format!(
                                 "Expected function, found {}",
-                                ctx.map.type_name(&ctx.map.get_var(fe).ty)
+                                ctx.map.type_name(&ctx.map.get_var(fe.id).ty)
                             ),
                         );
                         Type::Error
@@ -100,6 +117,7 @@ impl FnLowerable for PExpr {
                 temp
             }
             PExpr::Group(e) => e.lower(ctx)?,
+            PExpr::Construct(c) => todo!(),
         })
     }
 }
diff --git a/src/parser/v3/lower/func.rs b/src/parser/v3/lower/func.rs
index 9487fd0..e10b12b 100644
--- a/src/parser/v3/lower/func.rs
+++ b/src/parser/v3/lower/func.rs
@@ -1,8 +1,8 @@
-use super::{FnLowerable, Node, PFunction, ParserMsg, ParserOutput};
+use super::{CompilerMsg, CompilerOutput, FileSpan, FnLowerable, Node, PFunction};
 use crate::{
     ir::{
-        FileSpan, FnDef, FnID, IRInstructions, IRUFunction, IRUInstruction, Idents, NamespaceGuard,
-        Origin, Type, VarDef, VarID,
+        FnDef, FnID, IRInstructions, IRUFunction, IRUInstruction, Idents, NamespaceGuard, Origin,
+        Type, VarDef, VarID, VarInst,
     },
     parser,
 };
@@ -11,7 +11,7 @@ impl Node<PFunction> {
     pub fn lower_header(
         &self,
         map: &mut NamespaceGuard,
-        output: &mut ParserOutput,
+        output: &mut CompilerOutput,
     ) -> Option<FnID> {
         self.as_ref()?.lower_header(map, output)
     }
@@ -19,7 +19,7 @@ impl Node<PFunction> {
         &self,
         id: FnID,
         map: &mut NamespaceGuard,
-        output: &mut ParserOutput,
+        output: &mut CompilerOutput,
     ) -> Option<IRUFunction> {
         Some(self.as_ref()?.lower_body(id, map, output))
     }
@@ -29,7 +29,7 @@ impl PFunction {
     pub fn lower_header(
         &self,
         map: &mut NamespaceGuard,
-        output: &mut ParserOutput,
+        output: &mut CompilerOutput,
     ) -> Option<FnID> {
         let header = self.header.as_ref()?;
         let name = header.name.as_ref()?;
@@ -59,7 +59,7 @@ impl PFunction {
         &self,
         id: FnID,
         map: &mut NamespaceGuard,
-        output: &mut ParserOutput,
+        output: &mut CompilerOutput,
     ) -> IRUFunction {
         let mut instructions = IRInstructions::new();
         let def = map.get_fn(id).clone();
@@ -71,7 +71,7 @@ impl PFunction {
             span: self.body.span,
         };
         if let Some(src) = self.body.lower(&mut ctx) {
-            instructions.push(IRUInstruction::Ret { src });
+            instructions.push(IRUInstruction::Ret { src }, src.span);
         }
         IRUFunction::new(def.name.clone(), args, instructions)
     }
@@ -80,7 +80,7 @@ impl PFunction {
 pub struct FnLowerCtx<'a, 'n> {
     pub map: &'a mut NamespaceGuard<'n>,
     pub instructions: &'a mut IRInstructions,
-    pub output: &'a mut ParserOutput,
+    pub output: &'a mut CompilerOutput,
     pub span: FileSpan,
 }
 
@@ -101,7 +101,7 @@ impl<'n> FnLowerCtx<'_, 'n> {
         }
         res
     }
-    pub fn get_var(&mut self, node: &Node<parser::PIdent>) -> Option<VarID> {
+    pub fn get_var(&mut self, node: &Node<parser::PIdent>) -> Option<VarInst> {
         let ids = self.get(node)?;
         if ids.var.is_none() {
             self.err_at(
@@ -112,19 +112,25 @@ impl<'n> FnLowerCtx<'_, 'n> {
                 ),
             );
         }
-        ids.var
+        ids.var.map(|id| VarInst {
+            id,
+            span: node.span,
+        })
     }
     pub fn err(&mut self, msg: String) {
-        self.output.err(ParserMsg::from_span(self.span, msg))
+        self.output.err(CompilerMsg::from_span(self.span, msg))
     }
     pub fn err_at(&mut self, span: FileSpan, msg: String) {
-        self.output.err(ParserMsg::from_span(span, msg))
+        self.output.err(CompilerMsg::from_span(span, msg))
     }
-    pub fn temp(&mut self, ty: Type) -> VarID {
+    pub fn temp(&mut self, ty: Type) -> VarInst {
         self.map.temp_var(self.span, ty)
     }
     pub fn push(&mut self, i: IRUInstruction) {
-        self.instructions.push(i);
+        self.instructions.push(i, self.span);
+    }
+    pub fn push_at(&mut self, i: IRUInstruction, span: FileSpan) {
+        self.instructions.push(i, span);
     }
     pub fn sub<'b>(&'b mut self) -> FnLowerCtx<'b, 'n> {
         FnLowerCtx {
diff --git a/src/parser/v3/lower/module.rs b/src/parser/v3/lower/module.rs
index 22defa2..4d190c5 100644
--- a/src/parser/v3/lower/module.rs
+++ b/src/parser/v3/lower/module.rs
@@ -1,9 +1,9 @@
 use crate::ir::NamespaceGuard;
 
-use super::{PModule, ParserOutput};
+use super::{PModule, CompilerOutput};
 
 impl PModule {
-    pub fn lower(&self, map: &mut NamespaceGuard, output: &mut ParserOutput) {
+    pub fn lower(&self, map: &mut NamespaceGuard, output: &mut CompilerOutput) {
         let mut fns = Vec::new();
         for f in &self.functions {
             if let Some(id) = f.lower_header(map, output) {
diff --git a/src/parser/v3/mod.rs b/src/parser/v3/mod.rs
index 8d3f489..682858f 100644
--- a/src/parser/v3/mod.rs
+++ b/src/parser/v3/mod.rs
@@ -1,3 +1,4 @@
+mod ctx;
 mod cursor;
 mod error;
 mod lower;
@@ -5,13 +6,11 @@ mod node;
 mod nodes;
 mod parse;
 mod token;
-mod ctx;
 
+use crate::common::{CompilerMsg, CompilerOutput, FileSpan, FilePos};
+pub use ctx::*;
 pub use cursor::*;
-pub use error::*;
-pub use lower::*;
 pub use node::*;
 pub use nodes::*;
 pub use parse::*;
 pub use token::*;
-pub use ctx::*;
diff --git a/src/parser/v3/node.rs b/src/parser/v3/node.rs
index e591566..28eb2d7 100644
--- a/src/parser/v3/node.rs
+++ b/src/parser/v3/node.rs
@@ -3,7 +3,7 @@ use std::{
     ops::{Deref, DerefMut},
 };
 
-use crate::ir::FileSpan;
+use super::FileSpan;
 
 pub struct Node<T> {
     pub inner: Option<T>,
@@ -46,4 +46,3 @@ impl<T: Debug> Debug for Node<T> {
         }
     }
 }
-
diff --git a/src/parser/v3/nodes/asm_instr.rs b/src/parser/v3/nodes/asm_instr.rs
index e4305a0..4fdb04b 100644
--- a/src/parser/v3/nodes/asm_instr.rs
+++ b/src/parser/v3/nodes/asm_instr.rs
@@ -1,4 +1,4 @@
-use super::{PIdent, Node, Parsable, ParseResult, ParserCtx, ParserMsg, Symbol};
+use super::{Node, PIdent, Parsable, ParseResult, ParserCtx, Symbol, CompilerMsg};
 
 pub struct PInstruction {
     pub op: Node<PIdent>,
@@ -38,7 +38,7 @@ impl Parsable for PAsmArg {
 
         let next = ctx.expect_peek()?;
         if !next.is_symbol(Symbol::OpenCurly) {
-            return ParseResult::Err(ParserMsg::unexpected_token(
+            return ParseResult::Err(CompilerMsg::unexpected_token(
                 next,
                 "An identifier or {identifier}",
             ));
diff --git a/src/parser/v3/nodes/block.rs b/src/parser/v3/nodes/block.rs
index 62d09aa..7d62e66 100644
--- a/src/parser/v3/nodes/block.rs
+++ b/src/parser/v3/nodes/block.rs
@@ -1,7 +1,7 @@
 use std::fmt::{Debug, Write};
 
 use super::{
-    token::Symbol, Node, NodeParsable, Parsable, ParseResult, ParserCtx, ParserMsg, PStatement,
+    token::Symbol, Node, NodeParsable, PStatement, Parsable, ParseResult, ParserCtx, CompilerMsg,
 };
 use crate::util::Padder;
 
@@ -24,7 +24,7 @@ impl Parsable for PBlock {
         loop {
             let Some(next) = ctx.peek() else {
                 recover = true;
-                ctx.err(ParserMsg::unexpected_end());
+                ctx.err(CompilerMsg::unexpected_end());
                 break;
             };
             if next.is_symbol(Symbol::CloseCurly) {
@@ -36,7 +36,7 @@ impl Parsable for PBlock {
                 expect_semi = false;
                 continue;
             } else if expect_semi {
-                ctx.err(ParserMsg {
+                ctx.err(CompilerMsg {
                     msg: "expected ';'".to_string(),
                     spans: vec![ctx.next_start().char_span()],
                 });
diff --git a/src/parser/v3/nodes/def.rs b/src/parser/v3/nodes/def.rs
index c0f0698..128ebb4 100644
--- a/src/parser/v3/nodes/def.rs
+++ b/src/parser/v3/nodes/def.rs
@@ -1,7 +1,8 @@
 use std::fmt::Debug;
 
 use super::{
-    PIdent, MaybeParsable, Node, Parsable, ParseResult, ParserCtx, ParserMsg, Symbol, Token, PType,
+    MaybeParsable, Node, PExpr, PIdent, PType, Parsable, ParseResult, ParserCtx, Symbol,
+    Token, CompilerMsg
 };
 
 pub struct PVarDef {
@@ -9,6 +10,11 @@ pub struct PVarDef {
     pub ty: Option<Node<PType>>,
 }
 
+pub struct PFieldDef {
+    pub name: Node<PIdent>,
+    pub val: Option<Node<PExpr>>,
+}
+
 impl Parsable for PVarDef {
     fn parse(ctx: &mut ParserCtx) -> ParseResult<Self> {
         let name = ctx.parse()?;
@@ -21,6 +27,21 @@ impl Parsable for PVarDef {
     }
 }
 
+impl Parsable for PFieldDef {
+    fn parse(ctx: &mut ParserCtx) -> ParseResult<Self> {
+        let name = ctx.parse()?;
+        if ctx.peek().is_some_and(|n| n.is_symbol(Symbol::Colon)) {
+            ctx.next();
+            ctx.parse().map(|ty| Self {
+                name,
+                val: Some(ty),
+            })
+        } else {
+            ParseResult::Ok(Self { name, val: None })
+        }
+    }
+}
+
 pub struct SelfVar {
     pub ty: SelfType,
 }
@@ -32,7 +53,7 @@ pub enum SelfType {
 }
 
 impl MaybeParsable for SelfVar {
-    fn maybe_parse(ctx: &mut ParserCtx) -> Result<Option<Self>, super::ParserMsg> {
+    fn maybe_parse(ctx: &mut ParserCtx) -> Result<Option<Self>, CompilerMsg> {
         if let Some(mut next) = ctx.peek() {
             let mut ty = SelfType::Take;
             if next.is_symbol(Symbol::Ampersand) {
@@ -47,7 +68,7 @@ impl MaybeParsable for SelfVar {
                 }
             }
             if ty != SelfType::Take {
-                return Err(ParserMsg::unexpected_token(next, "self"));
+                return Err(CompilerMsg::unexpected_token(next, "self"));
             }
         }
         Ok(None)
@@ -64,6 +85,16 @@ impl Debug for PVarDef {
     }
 }
 
+impl Debug for PFieldDef {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        self.name.fmt(f)?;
+        if let Some(val) = &self.val {
+            write!(f, ": {:?}", val)?;
+        }
+        Ok(())
+    }
+}
+
 impl Debug for SelfVar {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         write!(
diff --git a/src/parser/v3/nodes/expr.rs b/src/parser/v3/nodes/expr.rs
index 04ddcd4..f0c507f 100644
--- a/src/parser/v3/nodes/expr.rs
+++ b/src/parser/v3/nodes/expr.rs
@@ -1,10 +1,7 @@
 use std::fmt::{Debug, Write};
 
 use super::{
-    op::{PInfixOp, UnaryOp},
-    util::parse_list,
-    PAsmBlock, PBlock, PIdent, Keyword, PLiteral, Node, NodeParsable, Parsable, ParseResult, ParserCtx,
-    ParserMsg, Symbol,
+    op::{PInfixOp, UnaryOp}, util::parse_list, Keyword, Node, NodeParsable, PAsmBlock, PBlock, PConstruct, PIdent, PLiteral, Parsable, ParseResult, ParserCtx, Symbol, CompilerMsg
 };
 
 type BoxNode = Node<Box<PExpr>>;
@@ -18,6 +15,7 @@ pub enum PExpr {
     Call(BoxNode, Vec<Node<PExpr>>),
     Group(BoxNode),
     AsmBlock(Node<PAsmBlock>),
+    Construct(Node<PConstruct>),
 }
 
 impl Parsable for PExpr {
@@ -63,7 +61,7 @@ impl Parsable for PExpr {
                 Self::Ident(res.node)
             } else {
                 let next = ctx.expect_peek()?;
-                return ParseResult::Err(ParserMsg::unexpected_token(next, "an expression"));
+                return ParseResult::Err(CompilerMsg::unexpected_token(next, "an expression"));
             }
         };
         let Some(mut next) = ctx.peek() else {
@@ -140,6 +138,7 @@ impl Debug for PExpr {
             }
             PExpr::Group(inner) => inner.fmt(f)?,
             PExpr::AsmBlock(inner) => inner.fmt(f)?,
+            PExpr::Construct(inner) => inner.fmt(f)?,
         }
         Ok(())
     }
diff --git a/src/parser/v3/nodes/ident.rs b/src/parser/v3/nodes/ident.rs
index d329d77..bb80ffd 100644
--- a/src/parser/v3/nodes/ident.rs
+++ b/src/parser/v3/nodes/ident.rs
@@ -1,4 +1,4 @@
-use super::{MaybeParsable, Parsable, ParseResult, ParserCtx, ParserMsg, Token};
+use super::{MaybeParsable, Parsable, ParseResult, ParserCtx, Token, CompilerMsg};
 use std::{
     fmt::{Debug, Display},
     ops::Deref,
@@ -11,7 +11,7 @@ impl Parsable for PIdent {
     fn parse(ctx: &mut ParserCtx) -> ParseResult<Self> {
         let next = ctx.expect_peek()?;
         let Token::Word(name) = &next.token else {
-            return ParseResult::Err(ParserMsg::unexpected_token(next, "an identifier"));
+            return ParseResult::Err(CompilerMsg::unexpected_token(next, "an identifier"));
         };
         let name = name.to_string();
         ctx.next();
@@ -20,7 +20,7 @@ impl Parsable for PIdent {
 }
 
 impl MaybeParsable for PIdent {
-    fn maybe_parse(ctx: &mut ParserCtx) -> Result<Option<Self>, ParserMsg> {
+    fn maybe_parse(ctx: &mut ParserCtx) -> Result<Option<Self>, CompilerMsg> {
         let Some(next) = ctx.peek() else { return Ok(None) };
         let Token::Word(name) = &next.token else {
             return Ok(None);
diff --git a/src/parser/v3/nodes/lit.rs b/src/parser/v3/nodes/lit.rs
index f2ac6e9..dba05c1 100644
--- a/src/parser/v3/nodes/lit.rs
+++ b/src/parser/v3/nodes/lit.rs
@@ -1,4 +1,4 @@
-use super::{CharCursor, MaybeParsable, ParserCtx, ParserMsg, Symbol, Token};
+use super::{CharCursor, MaybeParsable, ParserCtx, CompilerMsg, Symbol, Token};
 use std::fmt::Debug;
 
 #[derive(Clone, PartialEq, Eq)]
@@ -17,7 +17,7 @@ pub struct PNumber {
 }
 
 impl MaybeParsable for PLiteral {
-    fn maybe_parse(ctx: &mut ParserCtx) -> Result<Option<Self>, ParserMsg> {
+    fn maybe_parse(ctx: &mut ParserCtx) -> Result<Option<Self>, CompilerMsg> {
         let inst = ctx.expect_peek()?;
         Ok(Some(match &inst.token {
             Token::Symbol(Symbol::SingleQuote) => {
@@ -37,7 +37,7 @@ impl MaybeParsable for PLiteral {
                 if !first.is_ascii_digit() {
                     return Ok(None);
                 }
-                let (whole, ty) = parse_whole_num(text);
+                let (whole, ty) = parse_whole_num(&text);
                 let mut num = PNumber {
                     whole,
                     decimal: None,
@@ -81,7 +81,7 @@ pub fn parse_whole_num(text: &str) -> (String, Option<String>) {
     (whole, if ty.is_empty() { None } else { Some(ty) })
 }
 
-pub fn string_from(cursor: &mut CharCursor) -> Result<String, ParserMsg> {
+pub fn string_from(cursor: &mut CharCursor) -> Result<String, CompilerMsg> {
     let mut str = String::new();
     loop {
         let c = cursor.expect_next()?;
diff --git a/src/parser/v3/nodes/module.rs b/src/parser/v3/nodes/module.rs
index 2f74e05..2db6556 100644
--- a/src/parser/v3/nodes/module.rs
+++ b/src/parser/v3/nodes/module.rs
@@ -1,5 +1,5 @@
 use super::{
-    PFunction, PImpl, Keyword, Node, Parsable, ParseResult, ParserCtx, ParserMsg,
+    PFunction, PImpl, Keyword, Node, Parsable, ParseResult, ParserCtx, CompilerMsg,
     PStruct, Symbol, Token, PTrait,
 };
 use std::fmt::Debug;
@@ -52,18 +52,18 @@ impl Parsable for PModule {
                         }
                     }
                     _ => {
-                        ctx.err(ParserMsg::unexpected_token(next, "a definition"));
+                        ctx.err(CompilerMsg::unexpected_token(next, "a definition"));
                         ctx.next();
                     }
                 }
             } else if next.is_symbol(Symbol::Semicolon) {
-                ctx.hint(ParserMsg::from_instances(
+                ctx.hint(CompilerMsg::from_instances(
                     &[next],
                     "unneeded semicolon".to_string(),
                 ));
                 ctx.next();
             } else {
-                ctx.err(ParserMsg::unexpected_token(next, "a definition"));
+                ctx.err(CompilerMsg::unexpected_token(next, "a definition"));
                 ctx.next();
             }
         }
diff --git a/src/parser/v3/nodes/struc.rs b/src/parser/v3/nodes/struc.rs
index a804c00..1f45755 100644
--- a/src/parser/v3/nodes/struc.rs
+++ b/src/parser/v3/nodes/struc.rs
@@ -1,8 +1,8 @@
 use std::fmt::Debug;
 
 use super::{
-    util::parse_list, PIdent, Keyword, Node, Parsable, ParseResult, ParserCtx, ParserMsg, Symbol,
-    PType, PVarDef,
+    util::parse_list, Keyword, Node, PExpr, PFieldDef, PIdent, PType, PVarDef, Parsable,
+    ParseResult, ParserCtx, CompilerMsg, Symbol,
 };
 
 #[derive(Debug)]
@@ -11,6 +11,12 @@ pub struct PStruct {
     pub fields: PStructFields,
 }
 
+#[derive(Debug)]
+pub struct PConstruct {
+    pub name: Node<PIdent>,
+    pub fields: PConstructFields,
+}
+
 #[derive(Debug)]
 pub enum PStructFields {
     Named(Vec<Node<PVarDef>>),
@@ -18,6 +24,13 @@ pub enum PStructFields {
     None,
 }
 
+#[derive(Debug)]
+pub enum PConstructFields {
+    Named(Vec<Node<PFieldDef>>),
+    Tuple(Vec<Node<PExpr>>),
+    None,
+}
+
 impl Parsable for PStruct {
     fn parse(ctx: &mut ParserCtx) -> ParseResult<Self> {
         ctx.expect_kw(Keyword::Struct)?;
@@ -33,7 +46,7 @@ impl Parsable for PStruct {
             ctx.next();
             PStructFields::Tuple(parse_list(ctx, Symbol::CloseParen)?)
         } else {
-            let msg = ParserMsg::unexpected_token(next, "`;`, `(`, or `{`");
+            let msg = CompilerMsg::unexpected_token(next, "`;`, `(`, or `{`");
             ctx.err(msg);
             return ParseResult::Recover(PStruct {
                 name,
@@ -43,3 +56,29 @@ impl Parsable for PStruct {
         ParseResult::Ok(PStruct { name, fields })
     }
 }
+
+impl Parsable for PConstruct {
+    fn parse(ctx: &mut ParserCtx) -> ParseResult<Self> {
+        ctx.expect_kw(Keyword::Struct)?;
+        let name = ctx.parse()?;
+        let next = ctx.expect_peek()?;
+        let fields = if next.is_symbol(Symbol::Semicolon) {
+            ctx.next();
+            PConstructFields::None
+        } else if next.is_symbol(Symbol::OpenCurly) {
+            ctx.next();
+            PConstructFields::Named(parse_list(ctx, Symbol::CloseCurly)?)
+        } else if next.is_symbol(Symbol::OpenParen) {
+            ctx.next();
+            PConstructFields::Tuple(parse_list(ctx, Symbol::CloseParen)?)
+        } else {
+            let msg = CompilerMsg::unexpected_token(next, "`;`, `(`, or `{`");
+            ctx.err(msg);
+            return ParseResult::Recover(PConstruct {
+                name,
+                fields: PConstructFields::None,
+            });
+        };
+        ParseResult::Ok(PConstruct { name, fields })
+    }
+}
diff --git a/src/parser/v3/nodes/ty.rs b/src/parser/v3/nodes/ty.rs
index e1b4e37..1756432 100644
--- a/src/parser/v3/nodes/ty.rs
+++ b/src/parser/v3/nodes/ty.rs
@@ -1,6 +1,6 @@
 use std::fmt::Debug;
 
-use super::{util::parse_list, Node, Parsable, ParseResult, ParserCtx, ParserMsg, Symbol, Token};
+use super::{util::parse_list, Node, Parsable, ParseResult, ParserCtx, CompilerMsg, Symbol, Token};
 
 pub struct PType {
     pub name: String,
@@ -19,7 +19,7 @@ impl Parsable for PType {
             }
         } else {
             let Token::Word(name) = &next.token else {
-                return ParseResult::Err(ParserMsg::unexpected_token(next, "a type identifier"));
+                return ParseResult::Err(CompilerMsg::unexpected_token(next, "a type identifier"));
             };
             let n = name.to_string();
             ctx.next();
diff --git a/src/parser/v3/nodes/util.rs b/src/parser/v3/nodes/util.rs
index e307c4f..e5e9c85 100644
--- a/src/parser/v3/nodes/util.rs
+++ b/src/parser/v3/nodes/util.rs
@@ -1,10 +1,10 @@
-use super::{Node, Parsable, ParserCtx, ParserMsg, Symbol};
+use super::{Node, Parsable, ParserCtx, CompilerMsg, Symbol};
 
 pub fn parse_list_sep<T: Parsable>(
     ctx: &mut ParserCtx,
     sep: Symbol,
     end: Symbol,
-) -> Result<Vec<Node<T>>, ParserMsg> {
+) -> Result<Vec<Node<T>>, CompilerMsg> {
     let mut vals = Vec::new();
     loop {
         let next = ctx.expect_peek()?;
@@ -29,14 +29,14 @@ pub fn parse_list_sep<T: Parsable>(
 pub fn parse_list<T: Parsable>(
     ctx: &mut ParserCtx,
     end: Symbol,
-) -> Result<Vec<Node<T>>, ParserMsg> {
+) -> Result<Vec<Node<T>>, CompilerMsg> {
     parse_list_sep(ctx, Symbol::Comma, end)
 }
 
 pub fn parse_list_nosep<T: Parsable>(
     ctx: &mut ParserCtx,
     end: Symbol,
-) -> Result<Vec<Node<T>>, ParserMsg> {
+) -> Result<Vec<Node<T>>, CompilerMsg> {
     let mut vals = Vec::new();
     loop {
         let next = ctx.expect_peek()?;
diff --git a/src/parser/v3/parse.rs b/src/parser/v3/parse.rs
index 1cc15cb..6292acb 100644
--- a/src/parser/v3/parse.rs
+++ b/src/parser/v3/parse.rs
@@ -3,14 +3,12 @@ use std::{
     ops::{ControlFlow, FromResidual, Try},
 };
 
-use crate::ir::FilePos;
-
-use super::{Node, ParserCtx, ParserMsg};
+use super::{CompilerMsg, FilePos, Node, ParserCtx};
 
 pub enum ParseResult<T> {
     Ok(T),
     Recover(T),
-    Err(ParserMsg),
+    Err(CompilerMsg),
     SubErr,
 }
 
@@ -26,7 +24,7 @@ impl<T> ParseResult<T> {
 
 impl<T> Try for ParseResult<T> {
     type Output = T;
-    type Residual = Option<ParserMsg>;
+    type Residual = Option<CompilerMsg>;
     fn from_output(output: Self::Output) -> Self {
         Self::Ok(output)
     }
@@ -50,8 +48,8 @@ impl<T> FromResidual for ParseResult<T> {
     }
 }
 
-impl<T> FromResidual<Result<Infallible, ParserMsg>> for ParseResult<T> {
-    fn from_residual(residual: Result<Infallible, ParserMsg>) -> Self {
+impl<T> FromResidual<Result<Infallible, CompilerMsg>> for ParseResult<T> {
+    fn from_residual(residual: Result<Infallible, CompilerMsg>) -> Self {
         match residual {
             Err(e) => Self::Err(e),
         }
@@ -115,14 +113,28 @@ pub trait Parsable: Sized {
     fn parse(ctx: &mut ParserCtx) -> ParseResult<Self>;
 }
 
-pub trait MaybeParsable: Sized {
-    fn maybe_parse(ctx: &mut ParserCtx) -> Result<Option<Self>, ParserMsg>;
+pub trait ParsableWith: Sized {
+    type Data;
+
+    fn parse(ctx: &mut ParserCtx, data: Self::Data) -> ParseResult<Self>;
 }
 
-impl<T: Parsable> Node<T> {
-    pub fn parse(ctx: &mut ParserCtx) -> NodeParseResult<T> {
+pub trait MaybeParsable: Sized {
+    fn maybe_parse(ctx: &mut ParserCtx) -> Result<Option<Self>, CompilerMsg>;
+}
+
+impl<T: Parsable> ParsableWith for T {
+    type Data = ();
+
+    fn parse(ctx: &mut ParserCtx, _: Self::Data) -> ParseResult<Self> {
+        T::parse(ctx)
+    }
+}
+
+impl<T: ParsableWith> Node<T> {
+    pub fn parse_with(ctx: &mut ParserCtx, data: T::Data) -> NodeParseResult<T> {
         let start = ctx.peek().map(|t| t.span.start).unwrap_or(FilePos::start());
-        let (inner, recover) = match T::parse(ctx) {
+        let (inner, recover) = match T::parse(ctx, data) {
             ParseResult::Ok(v) => (Some(v), false),
             ParseResult::Recover(v) => (Some(v), true),
             ParseResult::Err(e) => {
@@ -142,6 +154,12 @@ impl<T: Parsable> Node<T> {
     }
 }
 
+impl<T: Parsable> Node<T> {
+    pub fn parse(ctx: &mut ParserCtx) -> NodeParseResult<T> {
+        Node::parse_with(ctx, ())
+    }
+}
+
 impl<T: MaybeParsable> Node<T> {
     pub fn maybe_parse(ctx: &mut ParserCtx) -> Option<Self> {
         let start = ctx.next_start();
diff --git a/src/parser/v3/token/cursor.rs b/src/parser/v3/token/cursor.rs
index 765b378..4aa0fb3 100644
--- a/src/parser/v3/token/cursor.rs
+++ b/src/parser/v3/token/cursor.rs
@@ -1,7 +1,6 @@
 use std::{iter::Peekable, str::Chars};
 
-use super::super::ParserMsg;
-use crate::ir::FilePos;
+use super::super::{CompilerMsg, FilePos};
 
 pub struct CharCursor<'a> {
     chars: Peekable<Chars<'a>>,
@@ -15,12 +14,12 @@ impl CharCursor<'_> {
         self.advance();
         Some(res)
     }
-    pub fn expect(&mut self, c: char) -> Result<(), ParserMsg> {
+    pub fn expect(&mut self, c: char) -> Result<(), CompilerMsg> {
         let next = self.expect_next()?;
         if next == c {
             Ok(())
         } else {
-            Err(ParserMsg::at(
+            Err(CompilerMsg::at(
                 self.prev_pos,
                 format!("unexpected char '{next}'; expected '{c}'"),
             ))
@@ -46,8 +45,8 @@ impl CharCursor<'_> {
             self.next_pos.col += 1;
         }
     }
-    pub fn expect_next(&mut self) -> Result<char, ParserMsg> {
-        self.next().ok_or(ParserMsg::unexpected_end())
+    pub fn expect_next(&mut self) -> Result<char, CompilerMsg> {
+        self.next().ok_or(CompilerMsg::unexpected_end())
     }
     pub fn next_pos(&self) -> FilePos {
         self.next_pos
diff --git a/src/parser/v3/token/mod.rs b/src/parser/v3/token/mod.rs
index 2679231..0624702 100644
--- a/src/parser/v3/token/mod.rs
+++ b/src/parser/v3/token/mod.rs
@@ -7,8 +7,7 @@ use std::ops::Deref;
 pub use cursor::*;
 pub use keyword::*;
 pub use symbol::*;
-
-use crate::ir::FileSpan;
+use super::FileSpan;
 
 #[derive(Debug, PartialEq, Eq, Clone)]
 pub enum Token {