From 80f317a1eb3b2fa8b938efc8a290a6df4af20a01 Mon Sep 17 00:00:00 2001
From: Ivan Enderlin <ivan.enderlin@hoa-project.net>
Date: Thu, 13 Feb 2020 11:24:29 +0100
Subject: [PATCH] feat(interface-types) Ensure `ast::Type` is always
 well-formed.

As @MarkMcCaskey noted, `Type` can be corrupted because `field_names`
and `field_types` must have the same length. This patch removes the
public visibility, and adds methods like `new`, `add_field`,
`field_names` and `field_types` to encapsulate `Type` internal data.
---
 src/ast.rs             | 40 ++++++++++++++++++++++++++++++++++++++--
 src/decoders/binary.rs | 36 ++++++++++++++++--------------------
 2 files changed, 54 insertions(+), 22 deletions(-)

diff --git a/src/ast.rs b/src/ast.rs
index 4adf2f0..d8b82f5 100644
--- a/src/ast.rs
+++ b/src/ast.rs
@@ -87,10 +87,46 @@ pub struct Type<'input> {
     pub name: &'input str,
 
     /// The field names.
-    pub fields: Vec<&'input str>,
+    field_names: Vec<&'input str>,
 
     /// The field types.
-    pub types: Vec<InterfaceType>,
+    field_types: Vec<InterfaceType>,
+}
+
+impl<'input> Type<'input> {
+    /// Creates a new `Type`.
+    ///
+    /// The constructor panics if there is the length of `names` is
+    /// different than the length of `types`.
+    pub fn new(type_name: &'input str, names: Vec<&'input str>, types: Vec<InterfaceType>) -> Self {
+        assert_eq!(
+            names.len(),
+            types.len(),
+            "There must be the same number of field names than field types."
+        );
+
+        Self {
+            name: type_name,
+            field_names: names,
+            field_types: types,
+        }
+    }
+
+    /// Adds a new field to the type.
+    pub fn add_field(&mut self, name: &'input str, ty: InterfaceType) {
+        self.field_names.push(name);
+        self.field_types.push(ty);
+    }
+
+    /// Returns the field names.
+    pub fn field_names(&self) -> &Vec<&'input str> {
+        &self.field_names
+    }
+
+    /// Returns the field types.
+    pub fn field_types(&self) -> &Vec<InterfaceType> {
+        &self.field_types
+    }
 }
 
 /// Represents an adapter.
diff --git a/src/decoders/binary.rs b/src/decoders/binary.rs
index afa549a..027e8e5 100644
--- a/src/decoders/binary.rs
+++ b/src/decoders/binary.rs
@@ -293,11 +293,7 @@ fn types<'input, E: ParseError<&'input [u8]>>(
         consume!((input, type_fields) = list(input, string)?);
         consume!((input, type_types) = list(input, ty)?);
 
-        types.push(Type {
-            name: type_name,
-            fields: type_fields,
-            types: type_types,
-        });
+        types.push(Type::new(type_name, type_fields, type_types));
     }
 
     Ok((input, types))
@@ -479,11 +475,11 @@ fn forwards<'input, E: ParseError<&'input [u8]>>(
 ///             input_types: vec![InterfaceType::I32],
 ///             output_types: vec![InterfaceType::I32],
 ///         }],
-///         types: vec![Type {
-///             name: "ab",
-///             fields: vec!["cd", "e"],
-///             types: vec![InterfaceType::I32, InterfaceType::I32],
-///         }],
+///         types: vec![Type::new(
+///             "ab",
+///             vec!["cd", "e"],
+///             vec![InterfaceType::I32, InterfaceType::I32],
+///         )],
 ///         imports: vec![Import {
 ///             namespace: "a",
 ///             name: "b",
@@ -728,11 +724,11 @@ mod tests {
         ];
         let output = Ok((
             &[] as &[u8],
-            vec![Type {
-                name: "ab",
-                fields: vec!["cd", "e"],
-                types: vec![InterfaceType::I32, InterfaceType::I32],
-            }],
+            vec![Type::new(
+                "ab",
+                vec!["cd", "e"],
+                vec![InterfaceType::I32, InterfaceType::I32],
+            )],
         ));
 
         assert_eq!(types::<()>(input), output);
@@ -913,11 +909,11 @@ mod tests {
                     input_types: vec![InterfaceType::I32],
                     output_types: vec![InterfaceType::I32],
                 }],
-                types: vec![Type {
-                    name: "ab",
-                    fields: vec!["cd", "e"],
-                    types: vec![InterfaceType::I32, InterfaceType::I32],
-                }],
+                types: vec![Type::new(
+                    "ab",
+                    vec!["cd", "e"],
+                    vec![InterfaceType::I32, InterfaceType::I32],
+                )],
                 imports: vec![Import {
                     namespace: "a",
                     name: "b",