Make expression type optional in pushdown DSL

plugin/trino-base-jdbc/src/main/antlr4/io/trino/plugin/jdbc/expression/ConnectorExpressionPattern.g4

@@ -36,7 +36,7 @@ call
     ;
 
 expressionCapture
-    : identifier ':' type
+    : identifier (':' type)?
     ;
 
 type

plugin/trino-base-jdbc/src/main/java/io/trino/plugin/jdbc/expression/ExpressionCapture.java

@@ -19,6 +19,7 @@
 import io.trino.spi.expression.ConnectorExpression;
 
 import java.util.Objects;
+import java.util.Optional;
 
 import static io.trino.matching.Capture.newCapture;
 import static io.trino.plugin.base.expression.ConnectorExpressionPatterns.type;
@@ -29,17 +30,30 @@ public class ExpressionCapture
         extends ExpressionPattern
 {
     private final String name;
-    private final TypePattern type;
+    private final Optional<TypePattern> type;
 
     private final Capture<ConnectorExpression> capture = newCapture();
     private final Pattern<ConnectorExpression> pattern;
 
+    public ExpressionCapture(String name)
+    {
+        this(name, Optional.empty());
+    }
+
     public ExpressionCapture(String name, TypePattern type)
+    {
+        this(name, Optional.of(type));
+    }
+
+    public ExpressionCapture(String name, Optional<TypePattern> type)
     {
         this.name = requireNonNull(name, "name is null");
         this.type = requireNonNull(type, "type is null");
-        this.pattern = Pattern.typeOf(ConnectorExpression.class).capturedAs(capture)
-                .with(type().matching(type.getPattern()));
+        Pattern<ConnectorExpression> pattern = Pattern.typeOf(ConnectorExpression.class).capturedAs(capture);
+        if (type.isPresent()) {
+            pattern = pattern.with(type().matching(type.get().getPattern()));
+        }
+        this.pattern = pattern;
     }
 
     @Override
@@ -52,7 +66,7 @@ public Pattern<ConnectorExpression> getPattern()
     public void resolve(Captures captures, MatchContext matchContext)
     {
         matchContext.record(name, captures.get(capture));
-        type.resolve(captures, matchContext);
+        type.ifPresent(type -> type.resolve(captures, matchContext));
     }
 
     @Override
@@ -78,6 +92,9 @@ public int hashCode()
     @Override
     public String toString()
     {
-        return format("%s: %s", name, type);
+        if (type.isEmpty()) {
+            return name;
+        }
+        return format("%s: %s", name, type.get());
     }
 }

plugin/trino-base-jdbc/src/main/java/io/trino/plugin/jdbc/expression/ExpressionPatternBuilder.java

@@ -52,7 +52,7 @@ public ExpressionPattern visitExpressionCapture(ConnectorExpressionPatternParser
     {
         return new ExpressionCapture(
                 visit(context.identifier(), String.class),
-                visit(context.type(), TypePattern.class));
+                visitIfPresent(context.type(), TypePattern.class));
     }
 
     @Override

plugin/trino-base-jdbc/src/test/java/io/trino/plugin/jdbc/expression/TestExpressionMappingParser.java

@@ -26,6 +26,8 @@ public class TestExpressionMappingParser
     @Test
     public void testCapture()
     {
+        assertExpressionPattern("b", new ExpressionCapture("b"));
+
         assertExpressionPattern(
                 "b: bigint",
                 new ExpressionCapture(
@@ -52,6 +54,13 @@ public void testParameterizedType()
     @Test
     public void testCallPattern()
     {
+        assertExpressionPattern(
+                "is_null(a)",
+                new CallPattern(
+                        "is_null",
+                        List.of(new ExpressionCapture("a")),
+                        Optional.empty()));
+
         assertExpressionPattern(
                 "$like_pattern(a: varchar(n), b: varchar(m))",
                 new CallPattern(