valid: Check dependencies between functions calls

This commit enforces the forward dependency rules on the IR across
functions and their calls, this fixes a crash in a later stage of the
validator.

src/valid/handles.rs

@@ -131,7 +131,7 @@ impl super::Validator {
  }
  }
 
- let validate_function = |function: &_| -> Result<_, InvalidHandleError> {
+ let validate_function = |function_handle, function: &_| -> Result<_, InvalidHandleError> {
  let &crate::Function {
  name: _,
  ref arguments,
@@ -175,6 +175,7 @@ impl super::Validator {
  local_variables,
  global_variables,
  functions,
+ function_handle,
  )?;
  }
 
@@ -184,11 +185,11 @@ impl super::Validator {
  };
 
  for entry_point in entry_points.iter() {
- validate_function(&entry_point.function)?;
+ validate_function(None, &entry_point.function)?;
  }
 
- for (_function_handle, function) in functions.iter() {
- validate_function(function)?;
+ for (function_handle, function) in functions.iter() {
+ validate_function(Some(function_handle), function)?;
  }
 
  Ok(())
@@ -229,6 +230,8 @@ impl super::Validator {
  local_variables: &Arena<crate::LocalVariable>,
  global_variables: &Arena<crate::GlobalVariable>,
  functions: &Arena<crate::Function>,
+ // The handle of the current function or `None` if it's an entry point
+ current_function: Option<Handle<crate::Function>>,
  ) -> Result<(), InvalidHandleError> {
  let validate_constant = |handle| Self::validate_constant_handle(handle, constants);
  let validate_type = |handle| Self::validate_type_handle(handle, types);
@@ -373,6 +376,9 @@ impl super::Validator {
  }
  crate::Expression::CallResult(function) => {
  Self::validate_function_handle(function, functions)?;
+ if let Some(handle) = current_function {
+ handle.check_dep(function)?;
+ }
  }
  crate::Expression::AtomicResult { .. } => (),
  crate::Expression::ArrayLength(array) => {