Easier construction of ScalarAndMetadata (#18272)

## Which issue does this PR close?

- Follow on to #17986 from
@paleolimbot

## Rationale for this change

As we thread Field through more of the DataFusion APs, making it easy to
convert back and forth
will be increasingly important. We added `ScalarAndMetadata` and I think
it is a good idea to add
some helper methods to make it easy to create `ScalarAndMetadata`.

## What changes are included in this PR?

Add some From impls that make conversions easier 

## Are these changes tested?

By CI
## Are there any user-facing changes?

SOme new APIs

Author: alamb

datafusion/common/src/metadata.rs

@@ -60,7 +60,15 @@ impl ScalarAndMetadata {
         target_type: &DataType,
     ) -> Result<Self, DataFusionError> {
         let new_value = self.value().cast_to(target_type)?;
-        Ok(ScalarAndMetadata::new(new_value, self.metadata.clone()))
+        Ok(Self::new(new_value, self.metadata.clone()))
+    }
+}
+
+/// create a new ScalarAndMetadata from a ScalarValue without
+/// any metadata
+impl From<ScalarValue> for ScalarAndMetadata {
+    fn from(value: ScalarValue) -> Self {
+        Self::new(value, None)
     }
 }
 

datafusion/common/src/param_value.rs

@@ -115,12 +115,7 @@ impl ParamValues {
 
 impl From<Vec<ScalarValue>> for ParamValues {
     fn from(value: Vec<ScalarValue>) -> Self {
-        Self::List(
-            value
-                .into_iter()
-                .map(|v| ScalarAndMetadata::new(v, None))
-                .collect(),
-        )
+        Self::List(value.into_iter().map(ScalarAndMetadata::from).collect())
     }
 }
 
@@ -131,7 +126,7 @@ where
     fn from(value: Vec<(K, ScalarValue)>) -> Self {
         let value: HashMap<String, ScalarAndMetadata> = value
             .into_iter()
-            .map(|(k, v)| (k.into(), ScalarAndMetadata::new(v, None)))
+            .map(|(k, v)| (k.into(), ScalarAndMetadata::from(v)))
             .collect();
         Self::Map(value)
     }
@@ -144,7 +139,7 @@ where
     fn from(value: HashMap<K, ScalarValue>) -> Self {
         let value: HashMap<String, ScalarAndMetadata> = value
             .into_iter()
-            .map(|(k, v)| (k.into(), ScalarAndMetadata::new(v, None)))
+            .map(|(k, v)| (k.into(), ScalarAndMetadata::from(v)))
             .collect();
         Self::Map(value)
     }

datafusion/expr/src/expr.rs

@@ -47,6 +47,7 @@ use sqlparser::ast::{
 
 // Moved in 51.0.0 to datafusion_common
 pub use datafusion_common::metadata::FieldMetadata;
+use datafusion_common::metadata::ScalarAndMetadata;
 
 // This mirrors sqlparser::ast::NullTreatment but we need our own variant
 // for when the sql feature is disabled.
@@ -424,6 +425,14 @@ impl From<WindowFunction> for Expr {
     }
 }
 
+/// Create an [`Expr`] from an [`ScalarAndMetadata`]
+impl From<ScalarAndMetadata> for Expr {
+    fn from(value: ScalarAndMetadata) -> Self {
+        let (value, metadata) = value.into_inner();
+        Expr::Literal(value, metadata)
+    }
+}
+
 /// Create an [`Expr`] from an optional qualifier and a [`FieldRef`]. This is
 /// useful for creating [`Expr`] from a [`DFSchema`].
 ///

datafusion/sql/tests/cases/params.rs

@@ -754,7 +754,7 @@ fn test_update_infer_with_metadata() {
         ("$2", Some(uuid_field.clone().with_name("id").into())),
     ];
     let param_values = vec![
-        ScalarAndMetadata::new(ScalarValue::from("Turing"), None),
+        ScalarAndMetadata::from(ScalarValue::from("Turing")),
         ScalarAndMetadata::new(
             ScalarValue::FixedSizeBinary(16, Some(uuid_bytes)),
             Some(uuid_field.metadata().into()),
@@ -831,8 +831,8 @@ fn test_insert_infer_with_metadata() {
             ScalarValue::FixedSizeBinary(16, Some(uuid_bytes)),
             Some(uuid_field.metadata().into()),
         ),
-        ScalarAndMetadata::new(ScalarValue::from("Alan"), None),
-        ScalarAndMetadata::new(ScalarValue::from("Turing"), None),
+        ScalarAndMetadata::from(ScalarValue::from("Alan")),
+        ScalarAndMetadata::from(ScalarValue::from("Turing")),
     ];
 
     // Check a normal insert