Allow returns values to be ignored in try catch

A try catch statement does not need to decode the return values if it is not interested.

Signed-off-by: Sean Young <sean@mess.org>

src/sema/statements.rs

@@ -2238,7 +2238,7 @@ fn try_catch(
                 func_returns = vec![];
             }
 
-            if returns.len() != func_returns.len() {
+            if !returns.is_empty() && returns.len() != func_returns.len() {
                 diagnostics.push(Diagnostic::error(
                     expr.loc(),
                     format!(

tests/evm.rs

@@ -248,7 +248,7 @@ fn ethereum_solidity_tests() {
         })
         .sum();
 
-    assert_eq!(errors, 1038);
+    assert_eq!(errors, 1032);
 }
 
 fn set_file_contents(source: &str, path: &Path) -> (FileResolver, Vec<String>) {

tests/substrate_tests/calls.rs

@@ -216,6 +216,32 @@ fn try_catch_external_calls() {
     runtime.constructor(0, Vec::new());
     runtime.function_expect_failure("test", Vec::new());
 
+    let mut runtime = build_solidity(
+        r##"
+        contract c {
+            function test() public {
+                other o = new other();
+                int32 x = 0;
+                try o.test() {
+                    x = 1;
+                } catch (bytes c) {
+                    x = 2;
+                }
+                assert(x == 2);
+            }
+        }
+
+        contract other {
+            function test() public returns (int32, bool) {
+                revert("foo");
+            }
+        }
+        "##,
+    );
+
+    runtime.constructor(0, Vec::new());
+    runtime.function("test", Vec::new());
+
     let mut runtime = build_solidity(
         r##"
         contract c {