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Author	SHA1	Message	Date
Siegfried Pammer	20cb82db20	Add pretty tests for C# 10 improved definite assignment The decompiler's stake in the C# 10 "improved definite assignment" rules (dotnet/csharplang#4465) is the mirror image of the compiler feature: decompiled output must stay provably assigned when recompiled, and ideally should not need dummy initializers where the C# 10 rules prove assignment. OutVariableFlows (green) pins that out variables flowing through short-circuit operators, conditional access, ternaries, while/for conditions, exception filters, closures and generic/struct out parameters decompile to recompilable code in all four Roslyn 4 debug/opt configs. Probing these flow shapes found no CS0165-broken output: the decompiler either rewrites conditional access into explicit null-check chains or falls back to a dummy initializer. The lifted-negation shape '(!(x)) ?? true' documents a trap: the C# 10 rules do not cover it, so its dummy initializer is required. ImprovedDefiniteAssignment (Assert.Ignore'd, #829) is the desired output spec for the shapes where the decompiler keeps the conditional access and currently hoists the out variable with a 'default(T)' initializer that the C# 10 rules make redundant: '?? false' on int, generic and struct out parameters, and '== true' on chained conditional access in if and while conditions. All four configs compile the fixture and fail only at the output comparison; the EXPECTED_OUTPUT branches carry IL-equivalent inputs where the desired form lowers to different IL. Assisted-by: Claude:claude-fable-5:Claude Code	2 months ago

Author

SHA1

Message

Date

Siegfried Pammer

20cb82db20

Add pretty tests for C# 10 improved definite assignment

The decompiler's stake in the C# 10 "improved definite assignment"
rules (dotnet/csharplang#4465) is the mirror image of the compiler
feature: decompiled output must stay provably assigned when recompiled,
and ideally should not need dummy initializers where the C# 10 rules
prove assignment.

OutVariableFlows (green) pins that out variables flowing through
short-circuit operators, conditional access, ternaries, while/for
conditions, exception filters, closures and generic/struct out
parameters decompile to recompilable code in all four Roslyn 4
debug/opt configs. Probing these flow shapes found no CS0165-broken
output: the decompiler either rewrites conditional access into
explicit null-check chains or falls back to a dummy initializer.
The lifted-negation shape '(!(x)) ?? true' documents a trap: the
C# 10 rules do not cover it, so its dummy initializer is required.

ImprovedDefiniteAssignment (Assert.Ignore'd, #829) is the desired
output spec for the shapes where the decompiler keeps the conditional
access and currently hoists the out variable with a 'default(T)'
initializer that the C# 10 rules make redundant: '?? false' on int,
generic and struct out parameters, and '== true' on chained
conditional access in if and while conditions. All four configs
compile the fixture and fail only at the output comparison; the
EXPECTED_OUTPUT branches carry IL-equivalent inputs where the desired
form lowers to different IL.

Assisted-by: Claude:claude-fable-5:Claude Code

2 months ago

1 Commits (20cb82db202efe2e53fc1ece508434ba2f895d57)