From 24d028e2a2eeb332c03f5b8c84fde085d4c9edc4 Mon Sep 17 00:00:00 2001
From: Mackenzie Clark <mackenzie.a.z.c@gmail.com>
Date: Thu, 14 Feb 2019 18:19:18 -0800
Subject: [PATCH] impl error trait for ResolveError (#179)

---
 lib/runtime-core/src/error.rs | 26 ++++++++++++++++++++++++++
 lib/runtime-core/src/types.rs | 24 ++++++++++++++++++++++++
 2 files changed, 50 insertions(+)

diff --git a/lib/runtime-core/src/error.rs b/lib/runtime-core/src/error.rs
index b72c74242..734e11cff 100644
--- a/lib/runtime-core/src/error.rs
+++ b/lib/runtime-core/src/error.rs
@@ -1,6 +1,7 @@
 use crate::types::{
     FuncSig, GlobalDescriptor, MemoryDescriptor, MemoryIndex, TableDescriptor, TableIndex, Type,
 };
+use core::borrow::Borrow;
 use std::sync::Arc;
 
 pub type Result<T> = std::result::Result<T, Error>;
@@ -135,6 +136,31 @@ impl PartialEq for ResolveError {
     }
 }
 
+impl std::fmt::Display for ResolveError {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        match self {
+            ResolveError::ExportNotFound { name } => write!(f, "Export not found: {}", name),
+            ResolveError::ExportWrongType { name } => write!(f, "Export wrong type: {}", name),
+            ResolveError::Signature { expected, found } => {
+                let found = found
+                    .as_slice()
+                    .iter()
+                    .map(|p| p.to_string())
+                    .collect::<Vec<_>>()
+                    .join(", ");
+                let expected: &FuncSig = expected.borrow();
+                write!(
+                    f,
+                    "Parameters of type [{}] did not match signature {}",
+                    found, expected
+                )
+            }
+        }
+    }
+}
+
+impl std::error::Error for ResolveError {}
+
 /// This error type is produced by calling a wasm function
 /// exported from a module.
 ///
diff --git a/lib/runtime-core/src/types.rs b/lib/runtime-core/src/types.rs
index c6b3f0a2b..fd57bf12c 100644
--- a/lib/runtime-core/src/types.rs
+++ b/lib/runtime-core/src/types.rs
@@ -15,6 +15,12 @@ pub enum Type {
     F64,
 }
 
+impl std::fmt::Display for Type {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        write!(f, "{:?}", self)
+    }
+}
+
 /// Represents a WebAssembly value.
 ///
 /// As the number of types in WebAssembly expand,
@@ -292,6 +298,24 @@ impl FuncSig {
     }
 }
 
+impl std::fmt::Display for FuncSig {
+    fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
+        let params = self
+            .params
+            .iter()
+            .map(|p| p.to_string())
+            .collect::<Vec<_>>()
+            .join(", ");
+        let returns = self
+            .returns
+            .iter()
+            .map(|p| p.to_string())
+            .collect::<Vec<_>>()
+            .join(", ");
+        write!(f, "[{}] -> [{}]", params, returns)
+    }
+}
+
 pub trait LocalImport {
     type Local: TypedIndex;
     type Import: TypedIndex;