Make 'to' a required argument

src/ethereum-canister/candid.did

@@ -14,10 +14,11 @@ type setup_request = record {
 
 type estimate_gas_request = record {
     from: opt address;
-    to: opt address;
-    gas: opt u256;
+    to: address;
+    gas_limit: opt u256;
     gas_price: opt u256;
     value: opt u256;
+    // Hash of the method signature and encoded parameters. See the Ethereum contract ABI specification.
     data: opt blob;
 };
 

src/ethereum-canister/src/utils.rs

@@ -24,7 +24,7 @@ impl IntoCallOpts for EstimateGasRequest {
     fn into_call_opts(self) -> CallOpts {
         CallOpts {
             from: self.from.map(Into::into),
-            to: self.to.map(Into::into),
+            to: Some(self.to.into()),
             gas: self.gas_limit.map(Into::into),
             gas_price: self.gas_price.map(Into::into),
             value: self.value.map(Into::into),

src/ethereum-canister/tests/canister.rs

@@ -33,13 +33,14 @@ fn estimate_gas() {
             .unwrap(),
     };
     let request = EstimateGasRequest {
-        to: Some(
-            "0xdAC17F958D2ee523a2206206994597C13D831ec7" // usdt
-                .parse()
-                .unwrap(),
-        ),
+        from: None,
+        to: "0xdAC17F958D2ee523a2206206994597C13D831ec7" // usdt
+            .parse()
+            .unwrap(),
+        gas_limit: None,
+        gas_price: None,
+        value: None,
         data: Some(erc20_balance_of.encode()),
-        ..Default::default()
     };
 
     let gas: (Nat,) = call!(canister, "estimate_gas", request).unwrap();

src/interface/src/lib.rs

@@ -28,10 +28,10 @@ pub struct Erc721OwnerOfRequest {
     pub token_id: U256,
 }
 
-#[derive(Debug, Clone, PartialEq, Eq, CandidType, Deserialize, Default)]
+#[derive(Debug, Clone, PartialEq, Eq, CandidType, Deserialize)]
 pub struct EstimateGasRequest {
     pub from: Option<Address>,
-    pub to: Option<Address>,
+    pub to: Address,
     pub gas_limit: Option<U256>,
     pub gas_price: Option<U256>,
     pub value: Option<U256>,