From a3ab765efe831505179a5966b5546509cb862717 Mon Sep 17 00:00:00 2001
From: Greg Brown <gmb60@cam.ac.uk>
Date: Sat, 16 Jan 2021 12:35:13 +0000
Subject: Fix warnings in `chomp::ast`.

---
 src/chomp/ast/error.rs | 34 ++++++++++++++++++++++++++++++++--
 1 file changed, 32 insertions(+), 2 deletions(-)

(limited to 'src/chomp/ast/error.rs')

diff --git a/src/chomp/ast/error.rs b/src/chomp/ast/error.rs
index d2c49cd..7be5354 100644
--- a/src/chomp/ast/error.rs
+++ b/src/chomp/ast/error.rs
@@ -14,13 +14,43 @@ pub enum SubstituteError {
 
 impl From<SubstituteError> for syn::Error {
     fn from(e: SubstituteError) -> Self {
-        todo!()
+        match e {
+            SubstituteError::FreeParameter { span, .. } => {
+                Self::new(span.unwrap_or_else(Span::call_site), "unbound parameter")
+            }
+            SubstituteError::WrongArgCount { call, expected, span } => {
+                let msg = if call.args.len() == 1 {
+                    format!("this function takes {} arguments but 1 was supplied", expected)
+                } else {
+                    format!("this function takes {} arguments but {} were supplied", expected, call.args.len())
+                };
+
+                Self::new(span.unwrap_or_else(Span::call_site), msg)
+            }
+        }
     }
 }
 
 impl Display for SubstituteError {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        todo!()
+        match self {
+            Self::FreeParameter { param, span, name } => {
+                let start = span.unwrap_or_else(Span::call_site).start();
+                if let Some(name) = name {
+                    write!(f, "{}:{}: unbound parameter `{}`", start.line, start.column, name)
+                } else {
+                    write!(f, "{}:{}: unbound parameter '{}", start.line, start.column, param.index)
+                }
+            }
+            Self::WrongArgCount { call, expected, span } => {
+                let start = span.unwrap_or_else(Span::call_site).start();
+                if call.args.len() == 1 {
+                    write!(f, "{}:{}: this function takes {} arguments but 1 was supplied", start.line, start.column, expected)
+                } else {
+                    write!(f, "{}:{}: this function takes {} arguments but {} were supplied", start.line, start.column, expected, call.args.len())
+                }
+            }
+        }
     }
 }
 
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