diff --git a/crates/verifier/Cargo.toml b/crates/verifier/Cargo.toml
index d532a7b1..0122308e 100644
--- a/crates/verifier/Cargo.toml
+++ b/crates/verifier/Cargo.toml
@@ -17,3 +17,5 @@ keywords = ["compiler", "evm", "wasm", "smart-contract"]
 [dependencies]
 sonatina-ir = { path = "../ir", version = "0.0.3-alpha" }
 cranelift-entity = "0.112"
+rustc-hash = "2.0.0"
+smallvec = "1.13.2"
diff --git a/crates/verifier/src/error/kind.rs b/crates/verifier/src/error/kind.rs
index deb52bd4..58c45999 100644
--- a/crates/verifier/src/error/kind.rs
+++ b/crates/verifier/src/error/kind.rs
@@ -3,7 +3,7 @@ use std::fmt;
 use sonatina_ir::{
     insn::DisplayInsn,
     module::FuncRef,
-    types::{CompoundType, DisplayCompoundType, DisplayType},
+    types::{DisplayCompoundType, DisplayType},
     value::DisplayArgValue,
     Block, Function, Insn, Type, Value,
 };
@@ -22,7 +22,6 @@ pub enum ErrorKind {
     ValueIsNullReference(Value),
     BlockIsNullReference(Block),
     FunctionIsNullReference(FuncRef),
-    CompoundTypeIsNullReference(CompoundType),
     BranchToEntryBlock(Block),
     // SSA form errors
     ValueLeak(Value),
@@ -31,6 +30,31 @@ pub enum ErrorKind {
     InsnResultWrongType(Type),
     CalleeArgWrongType(Type),
     CalleeResultWrongType(Type),
+    CompoundTypeIsNullReference(Type),
+}
+
+impl ErrorKind {
+    pub fn ir_source(&self) -> IrSource {
+        use ErrorKind::*;
+
+        match *self {
+            PhiInEntryBlock(i) => IrSource::Insn(i),
+            EmptyBlock(b) => IrSource::Block(b),
+            TerminatorBeforeEnd(i)
+            | NotEndedByTerminator(i)
+            | InstructionMapMismatched(i)
+            | BranchBrokenLink(i) => IrSource::Insn(i),
+            ValueIsNullReference(v) => IrSource::Value(v),
+            BlockIsNullReference(b) | BranchToEntryBlock(b) => IrSource::Block(b),
+            FunctionIsNullReference(f) => IrSource::Callee(f),
+            ValueLeak(v) => IrSource::Value(v),
+            InsnArgWrongType(ty)
+            | InsnResultWrongType(ty)
+            | CalleeArgWrongType(ty)
+            | CalleeResultWrongType(ty)
+            | CompoundTypeIsNullReference(ty) => IrSource::Type(ty),
+        }
+    }
 }
 
 pub struct DisplayErrorKind<'a> {
@@ -83,7 +107,10 @@ impl<'a> fmt::Display for DisplayErrorKind<'a> {
                     "instruction references inexistent function, opaque ref: {func_ref:?}"
                 )
             }
-            CompoundTypeIsNullReference(cmpd_ty) => {
+            CompoundTypeIsNullReference(ty) => {
+                let Type::Compound(cmpd_ty) = ty else {
+                    unreachable!("badly formed error");
+                };
                 let cmpd_ty = DisplayCompoundType::new(cmpd_ty, &func.dfg);
                 write!(f, "instruction references inexistent value, {cmpd_ty}")
             }
@@ -114,3 +141,12 @@ impl<'a> fmt::Display for DisplayErrorKind<'a> {
         }
     }
 }
+
+#[derive(Debug, Clone, Copy)]
+pub enum IrSource {
+    Callee(FuncRef),
+    Block(Block),
+    Insn(Insn),
+    Value(Value),
+    Type(Type),
+}
diff --git a/crates/verifier/src/error/mod.rs b/crates/verifier/src/error/mod.rs
index 8cb1fe25..1f8935cd 100644
--- a/crates/verifier/src/error/mod.rs
+++ b/crates/verifier/src/error/mod.rs
@@ -1,21 +1,26 @@
-mod kind;
+pub mod kind;
+
 mod trace_info;
 
 pub use kind::ErrorKind;
 pub use trace_info::{TraceInfo, TraceInfoBuilder};
 
+use kind::DisplayErrorKind;
 use trace_info::DisplayTraceInfo;
 
 use std::{error, fmt};
 
+use cranelift_entity::entity_impl;
 use sonatina_ir::Function;
 
-use crate::error::kind::DisplayErrorKind;
+#[derive(Clone, Copy, PartialEq, Eq)]
+pub struct ErrorRef(u32);
+entity_impl!(ErrorRef, "err");
 
 /// Verifier error.
 #[derive(Debug, Clone, Copy)]
 pub struct ErrorData {
-    kind: ErrorKind,
+    pub kind: ErrorKind,
     trace_info: TraceInfo,
 }
 
diff --git a/crates/verifier/src/error_stack.rs b/crates/verifier/src/error_stack.rs
new file mode 100644
index 00000000..a9ef2d5a
--- /dev/null
+++ b/crates/verifier/src/error_stack.rs
@@ -0,0 +1,21 @@
+use cranelift_entity::PrimaryMap;
+use sonatina_ir::Function;
+
+use crate::error::{Error, ErrorData, ErrorRef};
+
+#[derive(Debug, Default)]
+pub struct ErrorStack {
+    pub errors: PrimaryMap<ErrorRef, ErrorData>,
+}
+
+impl ErrorStack {
+    pub fn push(&mut self, err: ErrorData) -> ErrorRef {
+        self.errors.push(err)
+    }
+
+    pub fn into_errs_iter(self, func: &Function) -> impl IntoIterator<Item = Error<'_>> {
+        self.errors
+            .into_iter()
+            .map(|(_, err)| Error::new(err, func))
+    }
+}
diff --git a/crates/verifier/src/lib.rs b/crates/verifier/src/lib.rs
index a91e7351..d32fd422 100644
--- a/crates/verifier/src/lib.rs
+++ b/crates/verifier/src/lib.rs
@@ -1 +1,2 @@
 pub mod error;
+pub mod error_stack;