Give more specific error messages (#881)

2 files changed, 12 insertions, 6 deletions

diff --git a/src/eval/args.rs b/src/eval/args.rs
index aadd7d54..8617bd93 100644
--- a/src/eval/args.rs
+++ b/src/eval/args.rs
@@ -158,7 +158,13 @@ impl Args {
     /// argument.
     pub fn finish(self) -> SourceResult<()> {
         if let Some(arg) = self.items.first() {
-            bail!(arg.span, "unexpected argument");
+            bail!(
+                arg.span,
+                match &arg.name {
+                    Some(name) => eco_format!("unexpected argument: {}", name),
+                    _ => eco_format!("unexpected argument"),
+                }
+            )
         }
         Ok(())
     }
diff --git a/src/eval/scope.rs b/src/eval/scope.rs
index e241cac5..f2207188 100644
--- a/src/eval/scope.rs
+++ b/src/eval/scope.rs
@@ -2,7 +2,7 @@ use std::collections::BTreeMap;
 use std::fmt::{self, Debug, Formatter};
 use std::hash::Hash;
 
-use ecow::EcoString;
+use ecow::{eco_format, EcoString};
 
 use super::{Library, Value};
 use crate::diag::StrResult;
@@ -42,7 +42,7 @@ impl<'a> Scopes<'a> {
             .chain(self.scopes.iter().rev())
             .chain(self.base.map(|base| base.global.scope()))
             .find_map(|scope| scope.get(var))
-            .ok_or("unknown variable")?)
+            .ok_or(eco_format!("unknown variable: {}", var))?)
     }
 
     /// Try to access a variable immutably in math.
@@ -51,7 +51,7 @@ impl<'a> Scopes<'a> {
             .chain(self.scopes.iter().rev())
             .chain(self.base.map(|base| base.math.scope()))
             .find_map(|scope| scope.get(var))
-            .ok_or("unknown variable")?)
+            .ok_or(eco_format!("unknown variable: {}", var))?)
     }
 
     /// Try to access a variable mutably.
@@ -61,8 +61,8 @@ impl<'a> Scopes<'a> {
             .find_map(|scope| scope.get_mut(var))
             .ok_or_else(|| {
                 match self.base.and_then(|base| base.global.scope().get(var)) {
-                    Some(_) => "cannot mutate a constant",
-                    _ => "unknown variable",
+                    Some(_) => eco_format!("cannot mutate a constant: {}", var),
+                    _ => eco_format!("unknown variable: {}", var),
                 }
             })?
     }