diff --git a/reid/src/mir/fmt.rs b/reid/src/mir/fmt.rs
index 1d1037e..68c0899 100644
--- a/reid/src/mir/fmt.rs
+++ b/reid/src/mir/fmt.rs
@@ -108,12 +108,13 @@ impl Display for FunctionDefinition {
 impl Display for FunctionDefinitionKind {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         match self {
-            Self::Local(block, _) => {
+            FunctionDefinitionKind::Local(block, _) => {
                 write!(f, "{}", block)?;
                 Ok(())
             }
-            Self::Extern(true) => write!(f, "<Imported Extern>"),
-            Self::Extern(false) => write!(f, "<Linked Extern>"),
+            FunctionDefinitionKind::Extern(true) => write!(f, "<Imported Extern>"),
+            FunctionDefinitionKind::Extern(false) => write!(f, "<Linked Extern>"),
+            FunctionDefinitionKind::Intrinsic(_) => write!(f, "<Intrinsic>"),
         }
     }
 }
diff --git a/reid/src/mir/implement.rs b/reid/src/mir/implement.rs
index 55f36d0..ccffdfc 100644
--- a/reid/src/mir/implement.rs
+++ b/reid/src/mir/implement.rs
@@ -675,6 +675,8 @@ pub enum EqualsIssue {
     AlreadyExtern(String, Metadata),
     #[error("Function {0} is already imported from another module")]
     ConflictWithImport(String),
+    #[error("Function is defined as an intrinsic")]
+    ExistsAsIntrinsic,
 }
 
 impl FunctionDefinition {
@@ -701,6 +703,7 @@ impl FunctionDefinition {
                     }
                 }
             }
+            FunctionDefinitionKind::Intrinsic(_) => Err(EqualsIssue::ExistsAsIntrinsic),
         }
     }
 }
diff --git a/reid/src/mir/mod.rs b/reid/src/mir/mod.rs
index d432090..6e32bdd 100644
--- a/reid/src/mir/mod.rs
+++ b/reid/src/mir/mod.rs
@@ -302,6 +302,8 @@ pub enum FunctionDefinitionKind {
     Local(Block, Metadata),
     /// True = imported from other module, False = Is user defined extern
     Extern(bool),
+    /// Intrinsic definition, defined within the compiler
+    Intrinsic(Block),
 }
 
 impl FunctionDefinition {
@@ -309,6 +311,7 @@ impl FunctionDefinition {
         match &self.kind {
             FunctionDefinitionKind::Local(block, _) => block.meta.clone(),
             FunctionDefinitionKind::Extern(_) => Metadata::default(),
+            FunctionDefinitionKind::Intrinsic(_) => Metadata::default(),
         }
     }
 
@@ -316,6 +319,7 @@ impl FunctionDefinition {
         match &self.kind {
             FunctionDefinitionKind::Local(_, metadata) => metadata.clone(),
             FunctionDefinitionKind::Extern(_) => Metadata::default(),
+            FunctionDefinitionKind::Intrinsic(_) => Metadata::default(),
         }
     }
 }