tuple unpack: twoValue => multiValue

[xushiwei]

No description provided.

[gemini-code-assist]

Summary of Changes

Hello @xushiwei, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request introduces a significant refactoring in how the system handles multiple return values, moving from a binary 'two-value' flag to a more explicit integer parameter (lhs) that specifies the exact number of left-hand side values expected. This change enhances the flexibility and clarity of function calls, type assertions, and indexing operations, allowing for better support of tuple unpacking and multi-value assignments throughout the codebase.

Highlights

• Refactored Multi-Value Handling: Replaced the boolean InstrFlagTwoValue with a more flexible lhs int parameter across several core functions (matchFuncCall, matchTypeCast, matchRcast, matchFuncType) to explicitly indicate the number of left-hand side values expected from an operation.
• API Changes in CodeBuilder: The CodeBuilder methods CallWith, CallWithEx, Index, UnaryOp, and TypeAssert have been updated to accept the new lhs int parameter, providing more granular control over multi-value assignments and expressions.
• Simplified Instruction Flags: Removed InstrFlagTwoValue and instrFlagOpFunc from InstrFlags as their functionality is now covered by the new lhs parameter, streamlining the instruction flag set.
• Test Suite Updates: All relevant test files (builtin_test.go, codebuild.go, error_msg_test.go, package_test.go, template.go, typeparams_test.go, unsafe_test.go, xgo_test.go) have been updated to align with the new function signatures and parameter usage.

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[gemini-code-assist]

Code Review

This pull request refactors the handling of multi-value returns by replacing the twoValue boolean flag with a more general lhs integer, representing the number of variables on the left-hand side of an assignment. This is a good direction for improving support for tuple unpacking.

My review has identified a couple of critical bugs where the new lhs parameter is not correctly propagated, and a high-severity issue where a check was not generalized to handle more than two return values. Addressing these will be important for the correctness and completeness of this feature.

[xgopilot]

Code Review Summary

This refactoring improves code clarity by replacing the InstrFlagTwoValue flag with an explicit lhs parameter. However, two critical bugs prevent this PR from working correctly.

Critical Issues

1. codebuild.go:2313 - lhs not forwarded to doUnaryOp (causes TestRecv failure)
2. codebuild.go:537 - lhs not forwarded to matchFuncCall

Both bugs pass hardcoded 0 instead of the lhs parameter, breaking multi-value operations like elem, ok := <-channel.

Recommendations

• Fix the two parameter forwarding bugs
• Run full test suite to verify all tests pass
• Consider updating remaining "twoValue" references in comments for consistency

The refactoring approach is sound—explicit parameters are clearer than flags—but the implementation needs completion.

[codecov]

Codecov Report

❌ Patch coverage is 97.01493% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 96.10%. Comparing base (697e433) to head (e68614e).
⚠️ Report is 17 commits behind head on main.

Files with missing lines	Patch %	Lines
codebuild.go	92.59%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #575      +/-   ##
==========================================
- Coverage   96.10%   96.10%   -0.01%     
==========================================
  Files          25       25              
  Lines        6837     6831       -6     
==========================================
- Hits         6571     6565       -6     
  Misses        198      198              
  Partials       68       68              

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