[Mono-dev] Problems building mono

[Neale Ferguson]

Earlier this week I started getting the following:

../../../external/corefx/src/System.Linq.Expressions/src/System/Linq/Expres
sions/Compiler/KeyedStack.cs(19,45): error CS1644: Feature `declaration
expression' cannot be used because it is not part of the C# 6.0 language
specification
../../../external/corefx/src/System.Linq.Expressions/src/System/Linq/Expres
sions/Compiler/KeyedStack.cs(28,40): error CS1644: Feature `declaration
expression' cannot be used because it is not part of the C# 6.0 language
specification
../../../external/corefx/src/System.Linq.Expressions/src/System/Linq/Expres
sions/Compiler/KeyedStack.cs(28,81): error CS1644: Feature `declaration
expression' cannot be used because it is not part of the C# 6.0 language
specification


Not sure what to do.