Reimplement DecompilerSettings.StaticLocalFunctions (was lost in the refactoring in #2077)

ICSharpCode.Decompiler/IL/Transforms/LocalFunctionDecompiler.cs

@@ -484,7 +484,27 @@ namespace ICSharpCode.Decompiler.IL.Transforms
 					break;
 				parametersToRemove++;
 			}
-			return new LocalFunctionMethod(method, method.Name, parametersToRemove, typeParametersToRemove);
+			return new LocalFunctionMethod(method, method.Name, CanBeStaticLocalFunction(), parametersToRemove, typeParametersToRemove);
+
+			bool CanBeStaticLocalFunction()
+			{
+				if (!context.Settings.StaticLocalFunctions)
+					return false;
+				// Cannot be static because there are closure parameters that will be removed
+				if (parametersToRemove > 0)
+					return false;
+				// no closure parameters, but static:
+				// we can safely assume, this local function can be declared static
+				if (method.IsStatic)
+					return true;
+				// the local function is used in conjunction with a lambda, which means,
+				// it is defined inside the display-class type
+				var declaringType = method.DeclaringTypeDefinition;
+				if (!declaringType.IsCompilerGenerated())
+					return false;
+				// if there are no instance fields, we can make it a static local function
+				return !declaringType.GetFields(f => !f.IsStatic).Any();
+			}
 		}
 
 		static void TransformToLocalFunctionReference(ILFunction function, CallInstruction useSite)

ICSharpCode.Decompiler/TypeSystem/Implementation/LocalFunctionMethod.cs

@@ -31,12 +31,13 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 	{
 		readonly IMethod baseMethod;
 
-		public LocalFunctionMethod(IMethod baseMethod, string name, int numberOfCompilerGeneratedParameters, int numberOfCompilerGeneratedTypeParameters)
+		public LocalFunctionMethod(IMethod baseMethod, string name, bool isStaticLocalFunction, int numberOfCompilerGeneratedParameters, int numberOfCompilerGeneratedTypeParameters)
 		{
 			if (baseMethod == null)
 				throw new ArgumentNullException(nameof(baseMethod));
 			this.baseMethod = baseMethod;
 			this.Name = name;
+			this.IsStaticLocalFunction = isStaticLocalFunction;
 			this.NumberOfCompilerGeneratedParameters = numberOfCompilerGeneratedParameters;
 			this.NumberOfCompilerGeneratedTypeParameters = numberOfCompilerGeneratedTypeParameters;
 		}
@@ -47,7 +48,8 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 				return false;
 			return baseMethod.Equals(other.baseMethod, typeNormalization)
 				&& NumberOfCompilerGeneratedParameters == other.NumberOfCompilerGeneratedParameters
-				&& NumberOfCompilerGeneratedTypeParameters == other.NumberOfCompilerGeneratedTypeParameters;
+				&& NumberOfCompilerGeneratedTypeParameters == other.NumberOfCompilerGeneratedTypeParameters
+				&& IsStaticLocalFunction == other.IsStaticLocalFunction;
 		}
 
 		public override bool Equals(object obj)
@@ -56,7 +58,8 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 				return false;
 			return baseMethod.Equals(other.baseMethod)
 				&& NumberOfCompilerGeneratedParameters == other.NumberOfCompilerGeneratedParameters
-				&& NumberOfCompilerGeneratedTypeParameters == other.NumberOfCompilerGeneratedTypeParameters;
+				&& NumberOfCompilerGeneratedTypeParameters == other.NumberOfCompilerGeneratedTypeParameters
+				&& IsStaticLocalFunction == other.IsStaticLocalFunction;
 		}
 		
 		public override int GetHashCode()
@@ -66,14 +69,14 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 
 		public override string ToString()
 		{
-			return string.Format("[LocalFunctionMethod: ReducedFrom={0}, Name={1}, NumberOfGeneratedParameters={2}, NumberOfCompilerGeneratedTypeParameters={3}]", ReducedFrom, Name, NumberOfCompilerGeneratedParameters, NumberOfCompilerGeneratedTypeParameters);
+			return string.Format("[LocalFunctionMethod: ReducedFrom={0}, Name={1}, NumberOfGeneratedParameters={2}, NumberOfCompilerGeneratedTypeParameters={3}, IsStaticLocalFunction={4}]", ReducedFrom, Name, NumberOfCompilerGeneratedParameters, NumberOfCompilerGeneratedTypeParameters, IsStaticLocalFunction);
 		}
 
 		internal int NumberOfCompilerGeneratedParameters { get; }
 
 		internal int NumberOfCompilerGeneratedTypeParameters { get; }
 
-		internal bool IsStaticLocalFunction => NumberOfCompilerGeneratedParameters == 0 && (baseMethod.IsStatic || (baseMethod.DeclaringTypeDefinition.IsCompilerGenerated() && !baseMethod.DeclaringType.GetFields(f => !f.IsStatic).Any()));
+		internal bool IsStaticLocalFunction { get; }
 
 		public IMember MemberDefinition => this;
 
@@ -89,7 +92,7 @@ namespace ICSharpCode.Decompiler.TypeSystem.Implementation
 		{
 			return new LocalFunctionMethod(
 				baseMethod.Specialize(substitution),
-				Name, NumberOfCompilerGeneratedParameters, NumberOfCompilerGeneratedTypeParameters);
+				Name, IsStaticLocalFunction, NumberOfCompilerGeneratedParameters, NumberOfCompilerGeneratedTypeParameters);
 		}
 		
 		IMember IMember.Specialize(TypeParameterSubstitution substitution)