fix: Address clippy warnings

- Collapse nested if statement in invariants.rs (clippy::collapsible_if)
- Collapse nested if statement in hash_join/exec.rs (clippy::collapsible_if)
- Use unwrap_or_else instead of unwrap_or for function calls in
  decorrelate_predicate_subquery.rs (clippy::or_fun_call)

Author: viirya

datafusion/expr/src/logical_plan/invariants.rs

@@ -237,16 +237,14 @@ pub fn check_subquery_expr(
             }
 
             // For struct expressions, validate that the number of fields matches
-            if is_struct {
-                if let Expr::ScalarFunction(ref func) = *subquery.expr {
-                    let num_tuple_cols = func.args.len();
-                    if num_tuple_cols != num_subquery_cols {
-                        return plan_err!(
-                            "The number of columns in the tuple ({}) must match the number of columns in the subquery ({})",
-                            num_tuple_cols,
-                            num_subquery_cols
-                        );
-                    }
+            if is_struct && let Expr::ScalarFunction(ref func) = *subquery.expr {
+                let num_tuple_cols = func.args.len();
+                if num_tuple_cols != num_subquery_cols {
+                    return plan_err!(
+                        "The number of columns in the tuple ({}) must match the number of columns in the subquery ({})",
+                        num_tuple_cols,
+                        num_subquery_cols
+                    );
                 }
             }
         }

datafusion/optimizer/src/decorrelate_predicate_subquery.rs

@@ -420,7 +420,7 @@ fn build_join(
                     let in_predicate = conditions
                         .into_iter()
                         .reduce(|acc, cond| acc.and(cond))
-                        .unwrap_or(lit(true));
+                        .unwrap_or_else(|| lit(true));
 
                     in_predicate.and(join_filter)
                 } else {
@@ -481,7 +481,7 @@ fn build_join(
                     conditions
                         .into_iter()
                         .reduce(|acc, cond| acc.and(cond))
-                        .unwrap_or(lit(true))
+                        .unwrap_or_else(|| lit(true))
                 } else {
                     // Regular scalar function, handle as before
                     let right_col = create_col_from_scalar_expr(right.deref(), alias)?;

datafusion/physical-plan/src/joins/hash_join/exec.rs

@@ -544,12 +544,10 @@ impl HashJoinExec {
         check_join_is_valid(&left_schema, &right_schema, &on)?;
 
         // Validate null_aware flag
-        if null_aware {
-            if !matches!(join_type, JoinType::LeftAnti) {
-                return plan_err!(
-                    "null_aware can only be true for LeftAnti joins, got {join_type}"
-                );
-            }
+        if null_aware && !matches!(join_type, JoinType::LeftAnti) {
+            return plan_err!(
+                "null_aware can only be true for LeftAnti joins, got {join_type}"
+            );
         }
 
         let (join_schema, column_indices) =