Fix converter crashes around freshness

cpp2rust/converter/converter.cpp

@@ -3138,6 +3138,7 @@ bool Converter::VisitStmtExpr(clang::StmtExpr *expr) {
       Convert(s);
     }
   }
+  SetFreshType(expr->getType());
   return false;
 }
 

cpp2rust/converter/models/converter_refcount.cpp

@@ -1770,9 +1770,7 @@ bool ConverterRefCount::VisitReturnStmt(clang::ReturnStmt *stmt) {
 
 bool ConverterRefCount::VisitStmtExpr(clang::StmtExpr *expr) {
   PushConversionKind push(*this, ConversionKind::FullRefCount);
-  Converter::VisitStmtExpr(expr);
-  SetFreshType(expr->getType());
-  return false;
+  return Converter::VisitStmtExpr(expr);
 }
 
 void ConverterRefCount::ConvertBinaryOperator(clang::BinaryOperator *expr) {

tests/unit/out/refcount/stmt_expr.rs

@@ -41,6 +41,15 @@ fn main_0() -> i32 {
             inner
         } == 100)
     );
+    {
+        counter.postfix_inc()
+    };
+    {
+        if (counter != 2) {
+            counter = 2;
+        }
+    };
+    assert!((counter == 2));
     return 0;
 }
 pub fn __cpp2rust_init_globals() {}

tests/unit/out/unsafe/stmt_expr.rs

@@ -43,6 +43,15 @@ unsafe fn main_0() -> i32 {
             inner
         }) == (100))
     );
+    {
+        counter.postfix_inc()
+    };
+    {
+        if ((counter) != (2)) {
+            counter = 2;
+        }
+    };
+    assert!(((counter) == (2)));
     return 0;
 }
 pub unsafe fn __cpp2rust_init_globals() {}

tests/unit/stmt_expr.cpp

@@ -32,5 +32,13 @@ int main() {
            });
            inner;
          }) == 100);
+
+  ({ counter++; });
+  __extension__({
+    if (counter != 2) {
+      counter = 2;
+    }
+  });
+  assert(counter == 2);
   return 0;
 }