%fixedarray.set_null is mis-used or mis-compiled on wasm backend

[bobzhang]

CompileError: WebAssembly.Module(): Compiling function #303 failed: expected 1 elements on the stack for fallthru, found 2 @+25643
CompileError: WebAssembly.Module(): Compiling function #190 failed: expected 1 elements on the stack for fallthru, found 2 @+16908
CompileError: WebAssembly.Module(): Compiling function #170 failed: expected 1 elements on the stack for fallthru, found 2 @+16294
Failed to run the test

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[peter-jerry-ye-code-review]

From the provided git diff output, here are three observations that might indicate potential issues or areas for improvement in the MoonBit code:

1. Commented-out Code and Inline Comments:

   -  self.set_length(index)
   +  // self.set_length(index)
   +  self.buf.set_null(index) 
   +  // comment out wasm compilation is find
   +  self.len = index

   The original line self.set_length(index) was commented out and replaced with two new lines. While this might be intentional, it's worth considering:

   • Consistency: Ensure that the new lines (self.buf.set_null(index) and self.len = index) achieve the same goal as the commented-out line. If not, there might be a functional discrepancy.
   • Documentation: The inline comment // comment out wasm compilation is find suggests that the change was made to accommodate WebAssembly (Wasm) compilation. It would be beneficial to document why this change was necessary for clarity and future reference.

2. Potential Logical Error:

   guard self.length() != 0
   

   This guard statement ensures that the array length is not zero before proceeding. However, the subsequent code assumes that the array has elements and directly accesses the last element (self.buffer()[index]). If the guard were to fail, it would raise an error, which might be the intended behavior. Nonetheless, it's crucial to ensure that the error handling or validation mechanism is robust and clear.

3. Code Readability and Maintainability:

   +  self.buf.set_null(index) 
   +  self.len = index

   The new lines introduced are more complex than the original single line (self.set_length(index)). While they might serve the same purpose, multiple lines can reduce readability. Consider:

   • Refactoring: If possible, refactor the code to maintain clarity and simplicity. For example, if self.set_length(index) was a concise and clear representation of the operation, it might be beneficial to keep it unless the new functionality cannot be encapsulated in a single method call.
   • Comments: Adding detailed comments explaining the rationale behind the changes can improve code maintainability, especially if the new lines are necessary due to specific underlying mechanisms or constraints (e.g., Wasm compilation).

In summary, the changes indicate a potential functional adjustment due to Wasm compilation, require careful validation to ensure they maintain the original intended functionality, and should be documented for clarity and maintainability.

[coveralls]

Pull Request Test Coverage Report for Build 3274

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 83.17%

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Totals
Change from base Build 3263:	0.0%
Covered Lines:	4077
Relevant Lines:	4902

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💛 - Coveralls