Box ShellError in Value::Error (#8375)

# Description

Our `ShellError` at the moment has a `std::mem::size_of<ShellError>` of
136 bytes (on AMD64). As a result `Value` directly storing the struct
also required 136 bytes (thanks to alignment requirements).

This change stores the `Value::Error` `ShellError` on the heap.

Pro:
- Value now needs just 80 bytes
- Should be 1 cacheline less (still at least 2 cachelines)

Con:
- More small heap allocations when dealing with `Value::Error`
  - More heap fragmentation
  - Potential for additional required memcopies

# Further code changes

Includes a small refactor of `try` due to a type mismatch in its large
match.

# User-Facing Changes

None for regular users.

Plugin authors may have to update their matches on `Value` if they use
`nu-protocol`

Needs benchmarking to see if there is a benefit in real world workloads.
**Update** small improvements in runtime for workloads with high volume
of values. Significant reduction in maximum resident set size, when many
values are held in memory.

# Tests + Formatting

crates/nu-command/src/formats/to/delimited.rs

@@ -16,7 +16,7 @@ fn from_value_to_delimited_string(
         }
         Value::List { vals, span } => table_to_delimited(vals, span, separator, config, head),
         // Propagate errors by explicitly matching them before the final case.
-        Value::Error { error } => Err(error.clone()),
+        Value::Error { error } => Err(*error.clone()),
         v => Err(make_unsupported_input_error(v, head, v.expect_span())),
     }
 }
@@ -122,7 +122,7 @@ fn to_string_tagged_value(
         Value::Date { val, .. } => Ok(val.to_string()),
         Value::Nothing { .. } => Ok(String::new()),
         // Propagate existing errors
-        Value::Error { error } => Err(error.clone()),
+        Value::Error { error } => Err(*error.clone()),
         _ => Err(make_unsupported_input_error(v, head, span)),
     }
 }

crates/nu-command/src/formats/to/json.rs

@@ -70,12 +70,12 @@ impl Command for ToJson {
             }
             .into_pipeline_data()),
             _ => Ok(Value::Error {
-                error: ShellError::CantConvert {
+                error: Box::new(ShellError::CantConvert {
                     to_type: "JSON".into(),
                     from_type: value.get_type().to_string(),
                     span,
                     help: None,
-                },
+                }),
             }
             .into_pipeline_data()),
         }
@@ -126,7 +126,7 @@ pub fn value_to_json_value(v: &Value) -> Result<nu_json::Value, ShellError> {
         ),
 
         Value::List { vals, .. } => nu_json::Value::Array(json_list(vals)?),
-        Value::Error { error } => return Err(error.clone()),
+        Value::Error { error } => return Err(*error.clone()),
         Value::Closure { .. } | Value::Block { .. } | Value::Range { .. } => nu_json::Value::Null,
         Value::Binary { val, .. } => {
             nu_json::Value::Array(val.iter().map(|x| nu_json::Value::U64(*x as u64)).collect())

crates/nu-command/src/formats/to/nuon.rs

@@ -101,7 +101,7 @@ pub fn value_to_string(v: &Value, span: Span) -> Result<String, ShellError> {
         // FIXME: make durations use the shortest lossless representation.
         Value::Duration { val, .. } => Ok(format!("{}ns", *val)),
         // Propagate existing errors
-        Value::Error { error } => Err(error.clone()),
+        Value::Error { error } => Err(*error.clone()),
         // FIXME: make filesizes use the shortest lossless representation.
         Value::Filesize { val, .. } => Ok(format!("{}b", *val)),
         Value::Float { val, .. } => {

crates/nu-command/src/formats/to/toml.rs

@@ -77,7 +77,7 @@ fn helper(engine_state: &EngineState, v: &Value) -> Result<toml::Value, ShellErr
             toml::Value::String(code)
         }
         Value::Nothing { .. } => toml::Value::String("<Nothing>".to_string()),
-        Value::Error { error } => return Err(error.clone()),
+        Value::Error { error } => return Err(*error.clone()),
         Value::Binary { val, .. } => toml::Value::Array(
             val.iter()
                 .map(|x| toml::Value::Integer(*x as i64))
@@ -118,12 +118,12 @@ fn toml_into_pipeline_data(
         }
         .into_pipeline_data()),
         _ => Ok(Value::Error {
-            error: ShellError::CantConvert {
+            error: Box::new(ShellError::CantConvert {
                 to_type: "TOML".into(),
                 from_type: value_type.to_string(),
                 span,
                 help: None,
-            },
+            }),
         }
         .into_pipeline_data()),
     }
@@ -137,7 +137,7 @@ fn value_to_toml_value(
     match v {
         Value::Record { .. } => helper(engine_state, v),
         // Propagate existing errors
-        Value::Error { error } => Err(error.clone()),
+        Value::Error { error } => Err(*error.clone()),
         _ => Err(ShellError::UnsupportedInput(
             format!("{:?} is not valid top-level TOML", v.get_type()),
             "value originates from here".into(),

crates/nu-command/src/formats/to/yaml.rs

@@ -79,7 +79,7 @@ pub fn value_to_yaml_value(v: &Value) -> Result<serde_yaml::Value, ShellError> {
         Value::Block { .. } => serde_yaml::Value::Null,
         Value::Closure { .. } => serde_yaml::Value::Null,
         Value::Nothing { .. } => serde_yaml::Value::Null,
-        Value::Error { error } => return Err(error.clone()),
+        Value::Error { error } => return Err(*error.clone()),
         Value::Binary { val, .. } => serde_yaml::Value::Sequence(
             val.iter()
                 .map(|x| serde_yaml::Value::Number(serde_yaml::Number::from(*x)))
@@ -111,12 +111,12 @@ fn to_yaml(input: PipelineData, head: Span) -> Result<PipelineData, ShellError>
         }
         .into_pipeline_data()),
         _ => Ok(Value::Error {
-            error: ShellError::CantConvert {
+            error: Box::new(ShellError::CantConvert {
                 to_type: "YAML".into(),
                 from_type: value.get_type().to_string(),
                 span: head,
                 help: None,
-            },
+            }),
         }
         .into_pipeline_data()),
     }