Fix (clippy) warnings in Rust generate code

Also fix (clippy) warnings in Rust tests

Tested against rustc version 1.63.0. After this is merged and the new
generator is released, additional flag `--all-targets` can be added to
`cargo test` in CI.

flatdata-generator/flatdata/generator/templates/rust/archive.jinja2

@@ -109,15 +109,13 @@ impl ::std::fmt::Debug for {{archive.name}} {
 }
 
 impl {{archive.name}} {
+    #[allow(unused_imports, unused_variables)]
     pub fn open(storage: flatdata::StorageHandle)
         -> ::std::result::Result<Self, flatdata::ResourceStorageError>
     {
-        #[allow(unused_imports)]
         use flatdata::SliceExt;
-        #[allow(unused_variables)]
         use flatdata::ResourceStorageError as Error;
         // extend lifetime since Rust cannot know that we reference a cache here
-        #[allow(unused_variables)]
         let extend = |x : Result<&[u8], Error>| -> Result<&'static [u8], Error> {x.map(|x| unsafe{std::mem::transmute(x)})};
 
         storage.read(&Self::signature_name("{{archive.name}}"), schema::{{ archive_ns }}::{{ archive.name | camel_to_snake_case | upper }})?;
@@ -129,17 +127,17 @@ impl {{archive.name}} {
         {% if [r] | vector_resources %}
             {% set t = fully_qualified_name(archive, r.referenced_structures[0].node) %}
             let resource = extend(storage.read("{{r.name}}", schema::{{ archive_ns }}::resources::{{ r.name | upper }}));
-            check("{{ r.name }}", |r| r.len(), max_size, resource.and_then(|x| <&[{{t}}]>::from_bytes(x)))?
+            check("{{ r.name }}", |r| r.len(), max_size, resource.and_then(<&[{{t}}]>::from_bytes))?
         {% elif [r] | instance_resources %}
             {% set t = fully_qualified_name(archive, r.referenced_structures[0].node) %}
             let resource = extend(storage.read("{{r.name}}", schema::{{ archive_ns }}::resources::{{ r.name | upper }}));
-            check("{{ r.name }}", |_| 0, max_size, resource.and_then(|x| {{t}}::from_bytes_slice(x)))?
+            check("{{ r.name }}", |_| 0, max_size, resource.and_then({{t}}::from_bytes_slice))?
         {% elif [r] | rawdata_resources %}
             let resource = extend(storage.read("{{r.name}}", schema::{{ archive_ns }}::resources::{{ r.name | upper }}));
-            check("{{ r.name }}", |r| r.len(), max_size, resource.map(|x| flatdata::RawData::new(x)))?
+            check("{{ r.name }}", |r| r.len(), max_size, resource.map(flatdata::RawData::new))?
         {% elif [r] | multivector_resources %}
             {% set i = fully_qualified_name(archive, r.index_reference.node) %}
-            let index_schema = &format!("index({})", schema::{{ archive_ns }}::resources::{{ r.name | upper }});
+            let index_schema = format!("index({})", schema::{{ archive_ns }}::resources::{{ r.name | upper }});
             let index = extend(storage.read("{{r.name}}_index", &index_schema));
             let data = extend(storage.read("{{r.name}}", schema::{{ archive_ns }}::resources::{{ r.name | upper }}));
             let result = match (index, data) {

flatdata-generator/flatdata/generator/templates/rust/structure.jinja2

@@ -11,6 +11,8 @@ pub struct {{struct.name}} {
 }
 
 impl {{ struct.name }} {
+    /// # Safety
+    ///
     /// Unsafe since the struct might not be self-contained
     pub unsafe fn new_unchecked( ) -> Self {
         Self{data : [0; {{ struct.size_in_bytes }}]}
@@ -45,6 +47,7 @@ impl {{ struct.name }} {
     }
 
     /// Create reference from byte array
+    #[allow(clippy::len_zero)]
     pub fn from_bytes_slice(data: &[u8]) -> Result<&Self, flatdata::ResourceStorageError> {
         // We cannot rely on TryFrom here, since it does not yet support > 33 bytes
         if data.len() < {{ struct.size_in_bytes }} {
@@ -57,6 +60,7 @@ impl {{ struct.name }} {
     }
 
     /// Create reference from byte array
+    #[allow(clippy::len_zero)]
     pub fn from_bytes_slice_mut(data: &mut [u8]) -> Result<&mut Self, flatdata::ResourceStorageError> {
         // We cannot rely on TryFrom here, since it does not yet support > 33 bytes
         if data.len() < {{ struct.size_in_bytes }} {
@@ -94,6 +98,7 @@ impl {{ struct.name }} {
     /// [`{{ field.range | escape_rust_keywords }}`]: #method.{{ field.range | escape_rust_keywords }}
     {% endif %}
     #[inline]
+    #[allow(clippy::useless_transmute)]
     pub fn {{ field.name | escape_rust_keywords }}(&self) -> {% if field.invalid_value %}Option<{{ field | field_type }}>{% else %}{{ field | field_type }}{% endif %} {
         let value = flatdata_read_bytes!({{ field | primitive_type }}, self.data.as_ptr(), {{ field.offset }}, {{ field.type.width }});
         {% if field.invalid_value %}
@@ -109,6 +114,7 @@ impl {{ struct.name }} {
     {{ field.doc | rust_doc }}
     {% endif %}
     #[inline]
+    #[allow(clippy::identity_op)]
     pub fn {{ field.range | escape_rust_keywords }}(&self) -> std::ops::Range<{% if field.invalid_value %}Option<{{ field | field_type }}>{% else %}{{ field | field_type }}{% endif %}> {
         let start = flatdata_read_bytes!({{ field.type.name }}, self.data.as_ptr(), {{ field.offset }}, {{ field.type.width }});
         let end = flatdata_read_bytes!({{ field.type.name }}, self.data.as_ptr(), {{ field.offset }} + {{ struct.size_in_bytes }} * 8, {{ field.type.width }});

flatdata-generator/flatdata/generator/templates/rust/variadic.jinja2

@@ -52,7 +52,7 @@ impl<'a> {{name}}Builder<'a> {
     ///
     /// [`{{type.node.name}}`]: struct.{{type.node.name}}.html
     #[inline]
-    pub fn add_{{ type.node.name | camel_to_snake_case }}<'b>(&'b mut self) -> &'b mut {{inner_type}} {
+    pub fn add_{{ type.node.name | camel_to_snake_case }}(&mut self) -> &mut {{inner_type}} {
         let old_len = self.data.len();
         let increment = 1 + <{{inner_type}} as flatdata::Struct>::SIZE_IN_BYTES;
         self.data.resize(old_len + increment, 0);
@@ -101,7 +101,7 @@ impl<'a> flatdata::VariadicStruct<'a> for {{name}} {
         match index {
             {% for type in types %}
             {% set inner_type = fully_qualified_name(archive, type.node) %}
-                {{loop.index0}} => {{name}}Ref::{{type.node.name}}({{inner_type}}::from_bytes_slice(&data).expect("Corrupted data")),
+                {{loop.index0}} => {{name}}Ref::{{type.node.name}}({{inner_type}}::from_bytes_slice(data).expect("Corrupted data")),
             {% endfor %}
             _ => panic!("invalid type index {} for variadic type {{name}}Ref", index),
         }

flatdata-generator/tests/generators/rust_expectations/archives/comments.rs.1

@@ -27,15 +27,13 @@ impl ::std::fmt::Debug for Foo {
 }
 
 impl Foo {
+    #[allow(unused_imports, unused_variables)]
     pub fn open(storage: flatdata::StorageHandle)
         -> ::std::result::Result<Self, flatdata::ResourceStorageError>
     {
-        #[allow(unused_imports)]
         use flatdata::SliceExt;
-        #[allow(unused_variables)]
         use flatdata::ResourceStorageError as Error;
         // extend lifetime since Rust cannot know that we reference a cache here
-        #[allow(unused_variables)]
         let extend = |x : Result<&[u8], Error>| -> Result<&'static [u8], Error> {x.map(|x| unsafe{std::mem::transmute(x)})};
 
         storage.read(&Self::signature_name("Foo"), schema::foo::FOO)?;
@@ -44,10 +42,9 @@ impl Foo {
             use flatdata::check_resource as check;
             let max_size = None;
             let resource = extend(storage.read("bar", schema::foo::resources::BAR));
-            check("bar", |r| r.len(), max_size, resource.map(|x| flatdata::RawData::new(x)))?
+            check("bar", |r| r.len(), max_size, resource.map(flatdata::RawData::new))?
         };
 
-
         Ok(Self {
             _storage: storage,
             bar,
@@ -115,15 +112,13 @@ impl ::std::fmt::Debug for Bar {
 }
 
 impl Bar {
+    #[allow(unused_imports, unused_variables)]
     pub fn open(storage: flatdata::StorageHandle)
         -> ::std::result::Result<Self, flatdata::ResourceStorageError>
     {
-        #[allow(unused_imports)]
         use flatdata::SliceExt;
-        #[allow(unused_variables)]
         use flatdata::ResourceStorageError as Error;
         // extend lifetime since Rust cannot know that we reference a cache here
-        #[allow(unused_variables)]
         let extend = |x : Result<&[u8], Error>| -> Result<&'static [u8], Error> {x.map(|x| unsafe{std::mem::transmute(x)})};
 
         storage.read(&Self::signature_name("Bar"), schema::bar::BAR)?;
@@ -132,10 +127,9 @@ impl Bar {
             use flatdata::check_resource as check;
             let max_size = None;
             let resource = extend(storage.read("foo", schema::bar::resources::FOO));
-            check("foo", |r| r.len(), max_size, resource.map(|x| flatdata::RawData::new(x)))?
+            check("foo", |r| r.len(), max_size, resource.map(flatdata::RawData::new))?
         };
 
-
         Ok(Self {
             _storage: storage,
             foo,

flatdata-generator/tests/generators/rust_expectations/archives/empty.rs.1

@@ -18,15 +18,13 @@ impl ::std::fmt::Debug for A {
 }
 
 impl A {
+    #[allow(unused_imports, unused_variables)]
     pub fn open(storage: flatdata::StorageHandle)
         -> ::std::result::Result<Self, flatdata::ResourceStorageError>
     {
-        #[allow(unused_imports)]
         use flatdata::SliceExt;
-        #[allow(unused_variables)]
         use flatdata::ResourceStorageError as Error;
         // extend lifetime since Rust cannot know that we reference a cache here
-        #[allow(unused_variables)]
         let extend = |x : Result<&[u8], Error>| -> Result<&'static [u8], Error> {x.map(|x| unsafe{std::mem::transmute(x)})};
 
         storage.read(&Self::signature_name("A"), schema::a::A)?;
@@ -54,4 +52,4 @@ impl ABuilder {
         flatdata::create_archive("A", schema::a::A, &storage)?;
         Ok(Self { storage })
     }
-}
+}