Improved display of some error and remove unimplemented! for UnexpectedImageLayout display (#2305)

It appeared to me quite often that I've it some error and the message was lost on display because some `Display` implementation don't record the cause. Improved some of those that I've spotted while debugging some bad code I had.

Also removed the `unimplemented` for `AccessError::UnexpectedImageLayout` and now giving a more descriptive message.

vulkano/src/command_buffer/traits.rs

@@ -482,22 +482,28 @@ impl Error for CommandBufferExecError {
 
 impl Display for CommandBufferExecError {
     fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), FmtError> {
-        write!(
+        let value = match self {
-            f,
+            CommandBufferExecError::AccessError {
-            "{}",
+                error,
-            match self {
+                command_name,
-                CommandBufferExecError::AccessError { .. } =>
+                command_offset,
-                    "access to a resource has been denied",
+                command_param,
-                CommandBufferExecError::OneTimeSubmitAlreadySubmitted => {
+            } => return write!(
-                    "the command buffer or one of the secondary command buffers it executes was \
+                f,
-                    created with the \"one time submit\" flag, but has already been submitted in \
+                "access to a resource has been denied on command {} (offset: {}, param: {}): {}",
-                    the past"
+                command_name, command_offset, command_param, error
-                }
+            ),
-                CommandBufferExecError::ExclusiveAlreadyInUse => {
+            CommandBufferExecError::OneTimeSubmitAlreadySubmitted => {
-                    "the command buffer or one of the secondary command buffers it executes is \
+                "the command buffer or one of the secondary command buffers it executes was \
-                    already in use was not created with the \"concurrent\" flag"
+                created with the \"one time submit\" flag, but has already been submitted in \
-                }
+                the past"
             }
-        )
+            CommandBufferExecError::ExclusiveAlreadyInUse => {
+                "the command buffer or one of the secondary command buffers it executes is \
+                already in use was not created with the \"concurrent\" flag"
+            }
+        };
+
+        write!(f, "{}", value)
     }
 }

vulkano/src/sync/future/mod.rs

@@ -502,26 +502,28 @@ impl Error for AccessError {}
 
 impl Display for AccessError {
     fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), FmtError> {
-        write!(
+        let value = match self {
-            f,
+            AccessError::AlreadyInUse => {
-            "{}",
+                "the resource is already in use, and there is no tracking of concurrent usages"
-            match self {
-                AccessError::AlreadyInUse => {
-                    "the resource is already in use, and there is no tracking of concurrent usages"
-                }
-                AccessError::UnexpectedImageLayout { .. } => {
-                    unimplemented!() // TODO: find a description
-                }
-                AccessError::ImageNotInitialized { .. } => {
-                    "trying to use an image without transitioning it from the undefined or \
-                    preinitialized layouts first"
-                }
-                AccessError::SwapchainImageNotAcquired => {
-                    "trying to use a swapchain image without depending on a corresponding acquire \
-                    image future"
-                }
             }
-        )
+            AccessError::UnexpectedImageLayout { allowed, requested } => {
+                return write!(
+                    f,
+                    "unexpected image layout: requested {:?}, allowed {:?}",
+                    allowed, requested
+                )
+            }
+            AccessError::ImageNotInitialized { .. } => {
+                "trying to use an image without transitioning it from the undefined or \
+                preinitialized layouts first"
+            }
+            AccessError::SwapchainImageNotAcquired => {
+                "trying to use a swapchain image without depending on a corresponding acquire \
+                image future"
+            }
+        };
+
+        write!(f, "{}", value,)
     }
 }
 
@@ -538,14 +540,12 @@ impl Error for AccessCheckError {}
 
 impl Display for AccessCheckError {
     fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), FmtError> {
-        write!(
+        match self {
-            f,
+            AccessCheckError::Denied(err) => {
-            "{}",
+                write!(f, "access to the resource has been denied: {}", err)
-            match self {
-                AccessCheckError::Denied(_) => "access to the resource has been denied",
-                AccessCheckError::Unknown => "the resource is unknown",
             }
-        )
+            AccessCheckError::Unknown => write!(f, "the resource is unknown"),
+        }
     }
 }