Check in initial diff engine and semantic analysis #2

Job	Run time
Test Suite (ubuntu-latest, stable)	23s
Security Audit	4m 58s
Test Suite (macos-latest, beta)	39s
Test Suite (windows-latest, stable)	37s
Test Suite (ubuntu-latest, beta)	31s
Test Suite (macos-latest, stable)	29s
Test Suite (windows-latest, beta)	31s
Build Release	0s
	8m 8s

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