Infer conservative read-only source effects for method contracts

crates/objects/src/code.rs

@@ -106,6 +106,40 @@ impl EndorCode {
         self.signature.as_ref()
     }
 
+    /// Conservative proof over validated instructions. Local assignment is not
+    /// automatically pure: shared-reference assignment may update its old value.
+    /// Unknown calls and writes remain unknown, even when they could be safe for
+    /// a particular invocation. New opcodes require an explicit audit here.
+    pub fn is_statically_read_only(&self) -> bool {
+        self.instructions.iter().all(|decoded| {
+            matches!(
+                decoded.instruction.opcode,
+                Opcode::Nop
+                    | Opcode::LoadConst
+                    | Opcode::LoadFast
+                    | Opcode::DeleteFast
+                    | Opcode::LoadGlobal
+                    | Opcode::PopTop
+                    | Opcode::Copy
+                    | Opcode::Swap
+                    | Opcode::PushNull
+                    | Opcode::ReturnValue
+                    | Opcode::JumpForward
+                    | Opcode::JumpBackward
+                    | Opcode::PopJumpIfFalse
+                    | Opcode::PopJumpIfTrue
+                    | Opcode::ToBool
+                    | Opcode::UnaryNot
+                    | Opcode::CompareOp
+                    | Opcode::LoadDeref
+                    | Opcode::LoadClosure
+                    | Opcode::LoadAttr
+                    | Opcode::BuildMap
+                    | Opcode::MakeFunction
+            )
+        })
+    }
+
     pub fn with_location(
         mut self,
         name: impl Into<String>,