Simplify error assertion using let-else pattern

Author: mlafeldt

crates/duckdb/src/appender/mod.rs

@@ -84,9 +84,6 @@ impl Appender<'_> {
     }
 
     /// Append a DEFAULT value to the current row
-    ///
-    /// This is called internally when `AppendDefault` is used in `append_row()`.
-    /// Users should use the `AppendDefault` marker type instead of calling this directly.
     #[inline]
     fn append_default(&mut self) -> Result<()> {
         let rc = unsafe { ffi::duckdb_append_default(self.app) };
@@ -405,7 +402,7 @@ mod test {
     }
 
     #[test]
-    fn test_append_default_with_const_default() -> Result<()> {
+    fn test_append_default() -> Result<()> {
         let db = Connection::open_in_memory()?;
         db.execute_batch(
             "CREATE TABLE test (
@@ -442,16 +439,10 @@ mod test {
         let db = Connection::open_in_memory()?;
         db.execute_batch("CREATE TABLE test (id INTEGER, name VARCHAR DEFAULT 'test')")?;
 
-        // AppendDefault should fail in prepared statements
         let mut stmt = db.prepare("INSERT INTO test VALUES (?, ?)")?;
         let result = stmt.execute(params![1, AppendDefault]);
 
-        assert!(result.is_err());
-        if let Err(Error::ToSqlConversionFailure(e)) = result {
-            assert!(e.to_string().contains("only valid for Appender operations"));
-        } else {
-            panic!("Expected ToSqlConversionFailure error");
-        }
+        assert!(matches!(result, Err(Error::ToSqlConversionFailure(_))));
 
         Ok(())
     }

crates/duckdb/src/pragma.rs

@@ -58,8 +58,6 @@ impl Sql {
 
     pub fn push_value(&mut self, value: &dyn ToSql) -> Result<()> {
         let value = value.to_sql()?;
-        // Note: AppendDefault is only meaningful for data insertion operations (Appender).
-        // Pragmas are configuration commands, so DEFAULT values don't apply.
         let value = match value {
             ToSqlOutput::Borrowed(v) => v,
             ToSqlOutput::Owned(ref v) => ValueRef::from(v),

crates/duckdb/src/statement.rs

@@ -531,9 +531,6 @@ impl Statement<'_> {
         let value = param.to_sql()?;
 
         let ptr = unsafe { self.stmt.ptr() };
-        // Note: DuckDB's C API only provides duckdb_append_default() for Appender operations.
-        // There is no duckdb_bind_default() function for prepared statements, so we must
-        // reject AppendDefault here.
         let value = match value {
             ToSqlOutput::Borrowed(v) => v,
             ToSqlOutput::Owned(ref v) => ValueRef::from(v),

crates/duckdb/src/types/to_sql.rs

@@ -2,7 +2,7 @@ use super::{Null, TimeUnit, Value, ValueRef};
 use crate::Result;
 use std::borrow::Cow;
 
-/// Empty struct that can be used in Appender params to indicate DEFAULT value.
+/// Marker type that can be used in Appender params to indicate DEFAULT value.
 ///
 /// This is useful when you want to append a row with some columns using their
 /// default values (as defined in the table schema). Unlike `Null` which explicitly