Used the <- >- icon on Xcode to open source compare. Discarded one change. Closed the source compare. Xcode crashed with the following (short copy). On restarting Xcode, it automatically opened the project. Then on Build, it crashed again. This only happens when the source compare is used. I tried: deleting derived data, opening package contents of the xcode.proj and deleting xcuserdata, closing project, restoring Xcode. This causes Xcode to re-index everything, which has worked in the past, but not now.
Path: /Applications/Xcode.app/Contents/MacOS/XcodeIdentifier: com.apple.dt.XcodeVersion: 11.7 (16142)Build Info: IDEFrameworks-16142000000000000~5 (11E801a)App Item ID: 497799835App External ID: 837417466Code Type: X86-64 (Native)Parent Process: ??? [1]Responsible: Xcode [47737]User ID: 503Date/Time: 2020-09-18 11:06:26.252 -0500OS Version: Mac OS X 10.15.4 (19E287)Report Version: 12Anonymous UUID: 79A51667-E346-704F-A7E9-60A204A762E4Sleep/Wake UUID: 58021CB1-DFF8-46F0-97C3-AF609DBF11C5Time Awake Since Boot: 170000 secondsTime Since Wake: 11000 secondsSystem Integrity Protection: enabledCrashed Thread: 0 Dispatch queue: com.apple.main-threadException Type: EXC_CRASH (SIGABRT)Exception Codes: 0x0000000000000000, 0x0000000000000000Exception Note: EXC_CORPSE_NOTIFYApplication Specific Information:ProductBuildVersion: 11E801aASSERTION FAILURE in /Library/Caches/com.apple.xbs/Sources/IDEFrameworks/IDEFrameworks-16142/IDEKit/Behaviors/Alerts/ShowEditorAlert/IDEShowEditorAlert.m:143Details: Assertion failed: [editorArea _canAddEditorAreaSplitAfterEditorAreaSplit:lastActiveEditorAreaSplit layout:IDEEditorMultipleSplitRelativeLayout_Default]Object: <IDEShowEditorAlert>Method: +_createEditorAreaSplitForEditorArea:lastActiveEditorAreaSplit:Thread: <NSThread: 0x7fd6b4c060e0>{number = 1, name = main}Open FDs: 57/9472