Test that short-circuiting actually short-circuits - #97
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`&&`/`||` and the ternary already had laziness tests, but only for the
AST interpreter (test_expr_eval.cpp's RightSideNotEvaluatedWhenShortCircuited
and OnlyChosenBranchEvaluates). The compiled path's own test asserted only
the RESULT -- which an eager compiler computes just as correctly -- so
nothing would have failed if the JumpIfFalse/JumpIfTrue the compiler emits
around the right operand or the untaken branch ever went away. The list
comprehensions' `if`/`if-else` clauses had the same gap in both engines:
their tests check the resulting list, which an eager implementation also
gets right.
Six tests that close it, each running a marker echo() from inside the
branch that must never run and asserting the exact echo output, so an
extra evaluation shows up as an extra line:
BytecodeCompiler.ShortCircuitDoesNotEvaluateRightOperandCompiled
BytecodeCompiler.TernaryOnlyEvaluatesChosenBranchCompiled
ListComprehension.ForIfSkipsBodyWhenConditionFails{Interpreted,Compiled}
ListComprehension.ForIfElseEvaluatesOnlyTheChosenBranch{Interpreted,Compiled}
Verified non-vacuous by mutation: inverting the VM's jumps in
bytecode_compiler.cpp fails all four compiled tests (and leaves the
interpreted ones passing), while making expr_eval.cpp's ListCompIf/
ListCompIfElse cases eager fails both interpreted ones. That second run is
also what showed the interpreted variants need an explicit ScopedVm(false)
-- a top-level list comprehension compiles by default, so without it they
were re-testing the VM.
No behavior change; the evaluator was already correct on all six.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
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What
&&/||and the ternary already had laziness tests, but only for the AST interpreter (test_expr_eval.cpp'sRightSideNotEvaluatedWhenShortCircuitedandOnlyChosenBranchEvaluates). The compiled path's own test (TernaryAndShortCircuitLogicalOps) asserts only the result — which an eager compiler computes just as correctly — so nothing would have failed if theJumpIfFalse/JumpIfTruethe compiler emits around the right operand or the untaken branch ever went away.The list comprehensions'
if/if-elseclauses had the same gap in both engines: their tests check the resulting list, which an eager implementation also gets right.Tests added
Each runs a marker
echo()from inside the branch that must never run, and asserts the exact echo output — an extra evaluation shows up as an extra line.BytecodeCompiler.ShortCircuitDoesNotEvaluateRightOperandCompiled&&and||, both directionsBytecodeCompiler.TernaryOnlyEvaluatesChosenBranchCompiledListComprehension.ForIfSkipsBodyWhenConditionFails{Interpreted,Compiled}ListComprehension.ForIfElseEvaluatesOnlyTheChosenBranch{Interpreted,Compiled}Verified non-vacuous by mutation
bytecode_compiler.cppexpr_eval.cpp'sListCompIf/ListCompIfElsecases eagerThat second run is also what showed the interpreted variants need an explicit
ScopedVm(false)— a top-level list comprehension compiles by default, so without it they were re-testing the VM.Result
No behavior change; the evaluator was already correct on all six cases. Full suite passes (865 tests), and again under
OSCAD_BYTECODE_VM=0and=1.Version bumped 0.32.0 → 0.32.1.
🤖 Generated with Claude Code