PrecompiledAssemblyException: Multiple precompiled assemblies with the same name Antlr3.Runtime.dll included or the current platform. Only one assembly with the same name is allowed per platform. Assembly paths:
Assets/Ludiq/Assemblies/Antlr3.Runtime.dll
Assets/Plugins/PlasticSCM/Editor/PlasticLib/Antlr3.Runtime.dll
UnityEditor.Scripting.ScriptCompilation.EditorBuildRules.ValidateAndGetNameToPrecompiledAssembly (UnityEditor.Scripting.ScriptCompilation.PrecompiledAssembly[] precompiledAssemblies) (at <d3ff43e972b043d1b3f49905ec5da738>:0)
UnityEditor.Scripting.ScriptCompilation.EditorBuildRules.ToScriptAssemblies (System.Collections.Generic.IDictionary`2[TKey,TValue] targetAssemblies, UnityEditor.Scripting.ScriptCompilation.ScriptAssemblySettings settings, UnityEditor.Scripting.ScriptCompilation.EditorBuildRules+CompilationAssemblies assemblies, System.Collections.Generic.HashSet`1[T] runUpdaterAssemblies) (at <d3ff43e972b043d1b3f49905ec5da738>:0)
UnityEditor.Scripting.ScriptCompilation.EditorBuildRules.GetAllScriptAssemblies (System.Collections.Generic.Dictionary`2[TKey,TValue] allSourceFiles, System.String projectDirectory, UnityEditor.Scripting.ScriptCompilation.ScriptAssemblySettings settings, UnityEditor.Scripting.ScriptCompilation.EditorBuildRules+CompilationAssemblies assemblies, System.Collections.Generic.HashSet`1[T] runUpdaterAssemblies, UnityEditor.Scripting.ScriptCompilation.EditorBuildRules+TargetAssemblyType onlyIncludeType) (at <d3ff43e972b043d1b3f49905ec5da738>:0)
UnityEditor.Scripting.ScriptCompilation.EditorCompilation.GetAllScriptAssembliesOfType (UnityEditor.Scripting.ScriptCompilation.ScriptAssemblySettings settings, UnityEditor.Scripting.ScriptCompilation.EditorBuildRules+TargetAssemblyType type) (at <d3ff43e972b043d1b3f49905ec5da738>:0)
UnityEditor.Scripting.ScriptCompilation.EditorCompilation.CompileCustomScriptAssemblies (UnityEditor.Scripting.ScriptCompilation.ScriptAssemblySettings scriptAssemblySettings, System.String tempBuildDirectory, UnityEditor.Scripting.ScriptCompilation.EditorScriptCompilationOptions options, UnityEditor.BuildTargetGroup platformGroup, UnityEditor.BuildTarget platform) (at <d3ff43e972b043d1b3f49905ec5da738>:0)
UnityEditor.Scripting.ScriptCompilation.EditorCompilation.CompileCustomScriptAssemblies (UnityEditor.Scripting.ScriptCompilation.EditorScriptCompilationOptions options, UnityEditor.BuildTargetGroup platformGroup, UnityEditor.BuildTarget platform) (at <d3ff43e972b043d1b3f49905ec5da738>:0)
UnityEditor.Scripting.ScriptCompilation.EditorCompilationInterface+<>c__DisplayClass40_0.<CompileCustomScriptAssemblies>b__0 () (at <d3ff43e972b043d1b3f49905ec5da738>:0)
UnityEditor.Scripting.ScriptCompilation.EditorCompilationInterface.EmitExceptionAsError[T] (System.Func`1[TResult] func, T returnValue) (at <d3ff43e972b043d1b3f49905ec5da738>:0)
UnityEditor.Scripting.ScriptCompilation.EditorCompilationInterface:CompileCustomScriptAssemblies(EditorScriptCompilationOptions, BuildTargetGroup, BuildTarget)
This appears to be causing a critical error for me. But it was fine in Unity 2019.4.1, when I upgraded to Unity 2019.4.9 I had a problem like this before then, but i solved it but closing and reopening Unity hub.
EDIT: I removed "editor" from the bolt version of the file, which seemed to fix the error but bolt seems to be fussing at me about it...