Per file option: strictNullChecks #50347
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Heya @weswigham, I've started to run the perf test suite on this PR at 171a3ee. You can monitor the build here. |
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Heya @weswigham, I've started to run the parallelized Definitely Typed test suite on this PR at 171a3ee. You can monitor the build here. |
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Heya @weswigham, I've started to run the extended test suite on this PR at 171a3ee. You can monitor the build here. |
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Heya @weswigham, I've started to run the diff-based user code test suite on this PR at 171a3ee. You can monitor the build here. |
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Followup to #49886 that adds the missing
strictNullCheckssupport. 171a3ee - the commit adding it - is probably larger than the rest of the PR combined, so it's probably worth reviewing separately. Plus, I definitely need to run extended test suites on this, given how much is mucks with howstrictNullChecksworks.Specifically,
strictNullChecksnow has no globally toggled behavior. Instead:undefinedandnullare widening or non-widening depending on the strictness of the expression use site.undefinedandnullare only syntactically excluded from unions in non-strict mode, rather than always being elided. This could be refined a bit to allow aliases to null/undefined or unions containing them, but I don't know how far that has to go to be reasonably compatible. This facilitates flowingnullandundefinedfrom a strict mode file into a loose mode one and allowing working with them there.nullandundefinedfrom its branch results in non-strict contexts, to emulate the visible bits of the prior global union evaporation behavior.