Turbopack: Fix compound assignment expression evaluation #85478
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Previously, the analyzer treated all assignment expressions the same way, evaluating them as their right-hand side value. This was incorrect for compound assignments (+=, -=, *=, |=, >>=, etc.), which compute a new value based on both the left and right operands. This commit distinguishes between simple assignments (=) and compound assignments. Simple assignments continue to evaluate to the right-hand side, while compound assignments are now properly marked as unknown values with side effects. Also adds tests for compound assignments in conditionals, covering bitshift operations (>>=, <<=, >>>=) and bitwise operations (|=, &=, ^=) with both numbers and bigints.
CodSpeed Performance ReportMerging #85478 will degrade performances by 7.28%Comparing Summary
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sokra
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Oct 31, 2025
…5593) Migrated from #85478 into this non-fork because we had some issues with our CI infra that should be fixed going forward: https://vercel.slack.com/archives/C04KC8A53T7/p1761862171772939 --- fixes #85474 Previously, the analyzer treated all assignment expressions the same way, evaluating them as their right-hand side value. This was incorrect for compound assignments (+=, -=, *=, |=, >>=, etc.), which compute a new value based on both the left and right operands. This commit distinguishes between simple assignments (=) and compound assignments. Simple assignments continue to evaluate to the right-hand side, while compound assignments are now properly marked as unknown values with side effects. Also adds tests for compound assignments in conditionals, covering bitshift operations (>>=, <<=, >>>=) and bitwise operations (|=, &=, ^=) with both numbers and bigints.
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fixes #85474
Previously, the analyzer treated all assignment expressions the same way, evaluating them as their right-hand side value. This was incorrect for compound assignments (+=, -=, *=, |=, >>=, etc.), which compute a new value based on both the left and right operands.
This commit distinguishes between simple assignments (=) and compound assignments. Simple assignments continue to evaluate to the right-hand side, while compound assignments are now properly marked as unknown values with side effects.
Also adds tests for compound assignments in conditionals, covering bitshift operations (>>=, <<=, >>>=) and bitwise operations (|=, &=, ^=) with both numbers and bigints.