feat: null-safe navigation (a?.b) and null-coalescing (a ?? b) - #707
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killme2008 wants to merge 1 commit into
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feat: null-safe navigation (a?.b) and null-coalescing (a ?? b)#707killme2008 wants to merge 1 commit into
killme2008 wants to merge 1 commit into
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Implements issue #608. - Lexer folds `?.` into the variable lexeme, keeping a per-segment '?' marker (e.g. "a?.b" -> segments ["a?", "b"]). - Reflector short-circuits to null on a null intermediate value when the segment is marked null-safe, instead of throwing NPE. - Parser recognizes the right-associative, short-circuiting `??` operator and rejects assignment to a null-safe target. - All code generators (ASM, interpreter, optimize, lambda, none) emit the short-circuit for `??`; a new BranchIfNotNilIR backs the interpreter. - Public variable-name APIs strip the '?' marker ("a?.b" reported as "a.b"). Semantics follow JS/Groovy: each `?.` guards only its own segment; use `a?.b?.c` to guard the whole chain.
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Closes #608.
What
Adds two operators to AviatorScript:
a?.b— if the guarded value is null, the property navigation short-circuits tonilinstead of throwing.a ?? b— returnsawhen it is not null, otherwise evaluates and returnsb(right operand is strictly short-circuited).Semantics
Follows JS / Groovy: each
?.guards only its own segment.a?.b.cguardsaonly — ifa.bis null, navigating.cstill throws. Guard the whole chain witha?.b?.c.??only tests fornil; it does not catch exceptions. The right operand is not evaluated when the left is non-null.Design
?.adds no new runtime operator. The lexer foldsa?.binto a single variable token, normalizing the lexeme to keep a per-segment?marker (a?.b→ segments["a?", "b"]). This marker rides along the existing variable-name path all the way toReflector, soAviatorJavaTypeand both code generators need no constructor changes.Reflector.fastGetPropertystrips the?, and short-circuits to null on a null intermediate value only for marked segments.??is a parser-level short-circuiting operator (like&&/||), placed at ternary precedence and right-associative. All fiveCodeGeneratorimplementations emit the short-circuit; the interpreter uses a newBranchIfNotNilIR.OptimizeCodeGeneratorrecords/replays it via delegate tokens, avoiding a newOperatorType.Public
getVariableNames()/getVariableFullNames()strip the marker, soa?.bis reported asa.b. Assignment to a null-safe target (a?.b = 1) is a syntax error.Tests
NullSafeUnitTest+NullSafeInterpretUnitTestcover both eval modes (ASM + interpreter) and both optimize levels (EVAL + COMPILE): null root / mid-chain, unguarded null throws, Java-bean getters,??value/short-circuit/right-associativity, ternary regression, assignment rejection, and variable-name normalization. Full suite green (892 existing + new).Known limitations (follow-ups)
?.combined with dynamic or mid-chain array indexing (foo.bars[0]?.name) is not supported yet (syntax error).?:— its token collides with the existing ternary"?:";??covers the default-value use case.