opaque Lean.noncomputableExt : TagDeclarationExtension

def Lean.addNoncomputable (env : Environment) (declName : Name) : Environment

Mark in the environment extension that the given declaration has been declared by the user as noncomputable.

@[export lean_is_noncomputable]

def Lean.isNoncomputable (env : Environment) (declName : Name) : Bool

Returns true when the given declaration is tagged noncomputable.