Improve external output in subexprs (#294)

crates/nu-protocol/src/pipeline_data.rs

@@ -37,16 +37,16 @@ pub enum PipelineData {
 }
 
 impl PipelineData {
-    pub fn new() -> PipelineData {
-        PipelineData::Value(Value::nothing())
+    pub fn new(span: Span) -> PipelineData {
+        PipelineData::Value(Value::Nothing { span })
     }
 
-    pub fn into_value(self) -> Value {
+    pub fn into_value(self, span: Span) -> Value {
         match self {
             PipelineData::Value(v) => v,
             PipelineData::Stream(s) => Value::List {
                 vals: s.collect(),
-                span: Span::unknown(), // FIXME?
+                span, // FIXME?
             },
         }
     }
@@ -140,11 +140,11 @@ impl PipelineData {
     }
 }
 
-impl Default for PipelineData {
-    fn default() -> Self {
-        PipelineData::new()
-    }
-}
+// impl Default for PipelineData {
+//     fn default() -> Self {
+//         PipelineData::new()
+//     }
+// }
 
 pub struct PipelineIterator(PipelineData);
 

crates/nu-protocol/src/shell_error.rs

@@ -82,7 +82,7 @@ pub enum ShellError {
 
     #[error("Can't convert to {0}.")]
     #[diagnostic(code(nu::shell::cant_convert), url(docsrs))]
-    CantConvert(String, #[label("can't convert to {0}")] Span),
+    CantConvert(String, String, #[label("can't convert {1} to {0}")] Span),
 
     #[error("Division by zero.")]
     #[diagnostic(code(nu::shell::division_by_zero), url(docsrs))]

crates/nu-protocol/src/value/mod.rs

@@ -87,7 +87,14 @@ impl Value {
     pub fn as_string(&self) -> Result<String, ShellError> {
         match self {
             Value::String { val, .. } => Ok(val.to_string()),
-            _ => Err(ShellError::CantConvert("string".into(), self.span()?)),
+            x => {
+                println!("{:?}", x);
+                Err(ShellError::CantConvert(
+                    "string".into(),
+                    x.get_type().to_string(),
+                    self.span()?,
+                ))
+            }
         }
     }
 
@@ -225,10 +232,8 @@ impl Value {
     }
 
     /// Create a new `Nothing` value
-    pub fn nothing() -> Value {
-        Value::Nothing {
-            span: Span::unknown(),
-        }
+    pub fn nothing(span: Span) -> Value {
+        Value::Nothing { span }
     }
 
     /// Follow a given column path into the value: for example accessing nth elements in a stream or list
@@ -425,7 +430,9 @@ impl Value {
 
 impl Default for Value {
     fn default() -> Self {
-        Value::nothing()
+        Value::Nothing {
+            span: Span::unknown(),
+        }
     }
 }