reintroduce maybe macro with a new name

Author: maxcountryman

src/parser.rs

@@ -34,6 +34,15 @@ macro_rules! parser_err {
     };
 }
 
+// Returns a successful result if the optional expression is some
+macro_rules! return_ok_if_some {
+    ($e:expr) => {{
+        if let Some(v) = $e {
+            return Ok(v);
+        }
+    }};
+}
+
 #[derive(PartialEq)]
 pub enum IsOptional {
     Optional,
@@ -192,7 +201,7 @@ impl Parser {
         // Note also that naively `SELECT date` looks like a syntax error because the `date` type
         // name is not followed by a string literal, but in fact in PostgreSQL it is a valid
         // expression that should parse as the column name "date".
-        if let Some(parsed) = self.maybe_parse(|parser| match parser.parse_data_type()? {
+        return_ok_if_some!(self.maybe_parse(|parser| match parser.parse_data_type()? {
             DataType::Interval => parser.parse_literal_interval(),
             // Single-quoted strings are parsed as custom data types, however this not desirable
             // when we are handling input like `"NOT 'a' NOT LIKE 'b'"` because this will produce a
@@ -204,9 +213,7 @@ impl Parser {
                 data_type,
                 value: parser.parse_literal_string()?,
             }),
-        }) {
-            return Ok(parsed);
-        }
+        }));
 
         let tok = self
             .next_token()
@@ -1975,11 +1982,9 @@ impl Parser {
             // A parsing error from `parse_derived_table_factor` indicates that the '(' we've
             // recently consumed does not start a derived table (cases 1, 2, or 4). Ignore the
             // error and back up to where we after the opening '('.
-            if let Some(parsed) =
+            return_ok_if_some!(
                 self.maybe_parse(|parser| parser.parse_derived_table_factor(NotLateral))
-            {
-                return Ok(parsed);
-            }
+            );
 
             // Inside the parentheses we expect to find a table factor
             // followed by some joins or another level of nesting.