feat: Support casting DateTime to Date and verse versa

crates/gitql-ast/src/types/date.rs

@@ -3,6 +3,7 @@ use std::any::Any;
 use crate::expression::Expr;
 use crate::expression::StringExpr;
 use crate::format_checker::is_valid_date_format;
+use crate::types::datetime::DateTimeType;
 
 use super::base::DataType;
 
@@ -52,4 +53,8 @@ impl DataType for DateType {
         }
         false
     }
+
+    fn can_perform_explicit_cast_op_to(&self) -> Vec<Box<dyn DataType>> {
+        vec![Box::new(DateTimeType)]
+    }
 }

crates/gitql-ast/src/types/datetime.rs

@@ -3,6 +3,7 @@ use std::any::Any;
 use crate::expression::Expr;
 use crate::expression::StringExpr;
 use crate::format_checker::is_valid_datetime_format;
+use crate::types::date::DateType;
 
 use super::base::DataType;
 
@@ -52,4 +53,8 @@ impl DataType for DateTimeType {
         }
         false
     }
+
+    fn can_perform_explicit_cast_op_to(&self) -> Vec<Box<dyn DataType>> {
+        vec![Box::new(DateType)]
+    }
 }

crates/gitql-core/src/values/datetime.rs

@@ -3,6 +3,7 @@ use std::cmp::Ordering;
 
 use super::base::Value;
 use super::boolean::BoolValue;
+use super::date::DateValue;
 
 use chrono::DateTime;
 use gitql_ast::types::base::DataType;
@@ -90,4 +91,11 @@ impl Value for DateTimeValue {
         }
         Err("Unexpected type to perform `<=` with".to_string())
     }
+
+    fn cast_op(&self, target_type: &Box<dyn DataType>) -> Result<Box<dyn Value>, String> {
+        if target_type.is_date() {
+            return Ok(Box::new(DateValue { value: self.value }));
+        }
+        Err("Unexpected type to perform `Cast` with".to_string())
+    }
 }

crates/gitql-parser/src/parse_cast.rs

@@ -106,7 +106,8 @@ fn cast_expression_or_error(
     }
 
     Err(Diagnostic::error(&format!(
-        "Unsupported `CAST` operator to type {}",
+        "Unsupported `CAST` operator from type `{}` to type `{}`",
+        value_type.literal(),
         target_type.literal(),
     ))
     .with_location(location)