Fix clippy warning and refactor BlockType (#966)

* remove ValueType from BlockType::Returns variant

not used

* return usize from BlockType::len_{params,results}

crates/wasmi/src/engine/block_type.rs

@@ -17,7 +17,7 @@ pub enum BlockTypeInner {
     /// A block type with no parameters and no results.
     Empty,
     /// A block type with no parameters and exactly one result.
-    Returns(ValueType),
+    Returns,
     /// A general block type with parameters and results.
     FuncType(DedupFuncType),
 }
@@ -53,8 +53,8 @@ impl BlockType {
     }
 
     /// Creates a [`BlockType`] with no parameters and a single result type.
-    fn returns(return_type: ValueType) -> Self {
-        Self::from_inner(BlockTypeInner::Returns(return_type))
+    fn returns(_return_type: ValueType) -> Self {
+        Self::from_inner(BlockTypeInner::Returns)
     }
 
     /// Creates a [`BlockType`] with parameters and results.
@@ -63,22 +63,22 @@ impl BlockType {
     }
 
     /// Returns the number of parameters of the [`BlockType`].
-    pub fn len_params(&self, engine: &Engine) -> u32 {
+    pub fn len_params(&self, engine: &Engine) -> usize {
         match &self.inner {
-            BlockTypeInner::Empty | BlockTypeInner::Returns(_) => 0,
+            BlockTypeInner::Empty | BlockTypeInner::Returns => 0,
             BlockTypeInner::FuncType(func_type) => {
-                engine.resolve_func_type(func_type, |func_type| func_type.params().len() as u32)
+                engine.resolve_func_type(func_type, |func_type| func_type.params().len())
             }
         }
     }
 
     /// Returns the number of results of the [`BlockType`].
-    pub fn len_results(&self, engine: &Engine) -> u32 {
+    pub fn len_results(&self, engine: &Engine) -> usize {
         match &self.inner {
             BlockTypeInner::Empty => 0,
-            BlockTypeInner::Returns(_) => 1,
+            BlockTypeInner::Returns => 1,
             BlockTypeInner::FuncType(func_type) => {
-                engine.resolve_func_type(func_type, |func_type| func_type.results().len() as u32)
+                engine.resolve_func_type(func_type, |func_type| func_type.results().len())
             }
         }
     }

crates/wasmi/src/engine/translator/control_frame.rs

@@ -108,7 +108,7 @@ impl BlockControlFrame {
     /// Returns an iterator over the registers holding the branching parameters of the [`BlockControlFrame`].
     pub fn branch_params(&self, engine: &Engine) -> RegisterSpanIter {
         self.branch_params
-            .iter(self.block_type().len_results(engine) as usize)
+            .iter(self.block_type().len_results(engine))
     }
 
     /// Returns the label for the branch destination of the [`BlockControlFrame`].
@@ -213,7 +213,7 @@ impl LoopControlFrame {
     /// Returns an iterator over the registers holding the branching parameters of the [`LoopControlFrame`].
     pub fn branch_params(&self, engine: &Engine) -> RegisterSpanIter {
         self.branch_params
-            .iter(self.block_type().len_params(engine) as usize)
+            .iter(self.block_type().len_params(engine))
     }
 
     /// Returns the label for the branch destination of the [`LoopControlFrame`].
@@ -383,7 +383,7 @@ impl IfControlFrame {
     /// Returns an iterator over the registers holding the branching parameters of the [`IfControlFrame`].
     pub fn branch_params(&self, engine: &Engine) -> RegisterSpanIter {
         self.branch_params
-            .iter(self.block_type().len_results(engine) as usize)
+            .iter(self.block_type().len_results(engine))
     }
 
     /// Returns the label for the branch destination of the [`IfControlFrame`].

crates/wasmi/src/engine/translator/visit.rs

@@ -131,8 +131,8 @@ impl<'a> VisitOperator<'a> for FuncTranslator {
         let fuel_instr = self.fuel_instr();
         let stack_height = BlockHeight::new(self.engine(), self.alloc.stack.height(), block_type)?;
         let end_label = self.alloc.instr_encoder.new_label();
-        let len_block_params = block_type.len_params(self.engine()) as usize;
-        let len_branch_params = block_type.len_results(self.engine()) as usize;
+        let len_block_params = block_type.len_params(self.engine());
+        let len_branch_params = block_type.len_results(self.engine());
         let branch_params = self.alloc_branch_params(len_block_params, len_branch_params)?;
         self.alloc.control_stack.push_frame(BlockControlFrame::new(
             block_type,
@@ -157,7 +157,7 @@ impl<'a> VisitOperator<'a> for FuncTranslator {
             return Ok(());
         }
         // Copy `loop` parameters over to where it expects its branch parameters.
-        let len_block_params = block_type.len_params(self.engine()) as usize;
+        let len_block_params = block_type.len_params(self.engine());
         self.alloc
             .stack
             .pop_n(len_block_params, &mut self.alloc.buffer.providers);
@@ -210,8 +210,8 @@ impl<'a> VisitOperator<'a> for FuncTranslator {
         let stack_height = BlockHeight::new(self.engine(), self.alloc.stack.height(), block_type)?;
         self.preserve_locals()?;
         let end_label = self.alloc.instr_encoder.new_label();
-        let len_block_params = block_type.len_params(self.engine()) as usize;
-        let len_branch_params = block_type.len_results(self.engine()) as usize;
+        let len_block_params = block_type.len_params(self.engine());
+        let len_branch_params = block_type.len_results(self.engine());
         let branch_params = self.alloc_branch_params(len_block_params, len_branch_params)?;
         let (reachability, fuel_instr) = match condition {
             TypedProvider::Const(condition) => {