diff --git a/lib/puppet/pops/migration/migration_checker.rb b/lib/puppet/pops/migration/migration_checker.rb
index 6d49e6b2e..6e38be8c6 100644
--- a/lib/puppet/pops/migration/migration_checker.rb
+++ b/lib/puppet/pops/migration/migration_checker.rb
@@ -1,5 +1,13 @@
 # This class defines the API of the MigrationChecker support.
 #
 class Puppet::Pops::Migration::MigrationChecker
 
+  def initialize()
+  end
+
+  def report_ambiguous_integer(o)
+  end
+
+  def report_ambiguous_float(o)
+  end
 end
\ No newline at end of file
diff --git a/lib/puppet/pops/validation/checker4_0.rb b/lib/puppet/pops/validation/checker4_0.rb
index 08e7015da..9b98c5fe4 100644
--- a/lib/puppet/pops/validation/checker4_0.rb
+++ b/lib/puppet/pops/validation/checker4_0.rb
@@ -1,765 +1,775 @@
 # A Validator validates a model.
 #
 # Validation is performed on each model element in isolation. Each method should validate the model element's state
 # but not validate its referenced/contained elements except to check their validity in their respective role.
 # The intent is to drive the validation with a tree iterator that visits all elements in a model.
 #
 #
 # TODO: Add validation of multiplicities - this is a general validation that can be checked for all
 #       Model objects via their metamodel. (I.e an extra call to multiplicity check in polymorph check).
 #       This is however mostly valuable when validating model to model transformations, and is therefore T.B.D
 #
 class Puppet::Pops::Validation::Checker4_0
   Issues = Puppet::Pops::Issues
   Model = Puppet::Pops::Model
 
   attr_reader :acceptor
+  attr_reader :migration_checker
+
   # Initializes the validator with a diagnostics producer. This object must respond to
   # `:will_accept?` and `:accept`.
   #
   def initialize(diagnostics_producer)
     @@check_visitor       ||= Puppet::Pops::Visitor.new(nil, "check", 0, 0)
     @@rvalue_visitor      ||= Puppet::Pops::Visitor.new(nil, "rvalue", 0, 0)
     @@hostname_visitor    ||= Puppet::Pops::Visitor.new(nil, "hostname", 1, 2)
     @@assignment_visitor  ||= Puppet::Pops::Visitor.new(nil, "assign", 0, 1)
     @@query_visitor       ||= Puppet::Pops::Visitor.new(nil, "query", 0, 0)
     @@top_visitor         ||= Puppet::Pops::Visitor.new(nil, "top", 1, 1)
     @@relation_visitor    ||= Puppet::Pops::Visitor.new(nil, "relation", 0, 0)
     @@idem_visitor        ||= Puppet::Pops::Visitor.new(self, "idem", 0, 0)
 
     @acceptor = diagnostics_producer
 
     # Use null migration checker unless given in context
-    @migration_checker ||= Puppet.lookup(:migration_checker) { Puppet::Pops::Migration::MigrationChecker.new() }
+    @migration_checker ||= (Puppet.lookup(:migration_checker) { Puppet::Pops::Migration::MigrationChecker.new() })
   end
 
   # Validates the entire model by visiting each model element and calling `check`.
   # The result is collected (or acted on immediately) by the configured diagnostic provider/acceptor
   # given when creating this Checker.
   #
   def validate(model)
     # tree iterate the model, and call check for each element
     check(model)
     model.eAllContents.each {|m| check(m) }
   end
 
   # Performs regular validity check
   def check(o)
     @@check_visitor.visit_this_0(self, o)
   end
 
   # Performs check if this is a vaid hostname expression
   # @param single_feature_name [String, nil] the name of a single valued hostname feature of the value's container. e.g. 'parent'
   def hostname(o, semantic, single_feature_name = nil)
     @@hostname_visitor.visit_this_2(self, o, semantic, single_feature_name)
   end
 
   # Performs check if this is valid as a query
   def query(o)
     @@query_visitor.visit_this_0(self, o)
   end
 
   # Performs check if this is valid as a relationship side
   def relation(o)
     @@relation_visitor.visit_this_0(self, o)
   end
 
   # Performs check if this is valid as a rvalue
   def rvalue(o)
     @@rvalue_visitor.visit_this_0(self, o)
   end
 
   # Performs check if this is valid as a container of a definition (class, define, node)
   def top(o, definition)
     @@top_visitor.visit_this_1(self, o, definition)
   end
 
   # Checks the LHS of an assignment (is it assignable?).
   # If args[0] is true, assignment via index is checked.
   #
   def assign(o, via_index = false)
     @@assignment_visitor.visit_this_1(self, o, via_index)
   end
 
   # Checks if the expression has side effect ('idem' is latin for 'the same', here meaning that the evaluation state
   # is known to be unchanged after the expression has been evaluated). The result is not 100% authoritative for
   # negative answers since analysis of function behavior is not possible.
   # @return [Boolean] true if expression is known to have no effect on evaluation state
   #
   def idem(o)
     @@idem_visitor.visit_this_0(self, o)
   end
 
   # Returns the last expression in a block, or the expression, if that expression is idem
   def ends_with_idem(o)
     if o.is_a?(Puppet::Pops::Model::BlockExpression)
       last = o.statements[-1]
       idem(last) ? last : nil
     else
       idem(o) ? o : nil
     end
   end
 
   #---ASSIGNMENT CHECKS
 
   def assign_VariableExpression(o, via_index)
     varname_string = varname_to_s(o.expr)
     if varname_string =~ Puppet::Pops::Patterns::NUMERIC_VAR_NAME
       acceptor.accept(Issues::ILLEGAL_NUMERIC_ASSIGNMENT, o, :varname => varname_string)
     end
     # Can not assign to something in another namespace (i.e. a '::' in the name is not legal)
     if acceptor.will_accept? Issues::CROSS_SCOPE_ASSIGNMENT
       if varname_string =~ /::/
         acceptor.accept(Issues::CROSS_SCOPE_ASSIGNMENT, o, :name => varname_string)
       end
     end
     # TODO: Could scan for reassignment of the same variable if done earlier in the same container
     #       Or if assigning to a parameter (more work).
     # TODO: Investigate if there are invalid cases for += assignment
   end
 
   def assign_AccessExpression(o, via_index)
     # Are indexed assignments allowed at all ? $x[x] = '...'
     if acceptor.will_accept? Issues::ILLEGAL_INDEXED_ASSIGNMENT
       acceptor.accept(Issues::ILLEGAL_INDEXED_ASSIGNMENT, o)
     else
       # Then the left expression must be assignable-via-index
       assign(o.left_expr, true)
     end
   end
 
   def assign_Object(o, via_index)
     # Can not assign to anything else (differentiate if this is via index or not)
     # i.e. 10 = 'hello' vs. 10['x'] = 'hello' (the root is reported as being in error in both cases)
     #
     acceptor.accept(via_index ? Issues::ILLEGAL_ASSIGNMENT_VIA_INDEX : Issues::ILLEGAL_ASSIGNMENT, o)
   end
 
   #---CHECKS
 
   def check_Object(o)
   end
 
   def check_Factory(o)
     check(o.current)
   end
 
   def check_AccessExpression(o)
     # Only min range is checked, all other checks are RT checks as they depend on the resulting type
     # of the LHS.
     if o.keys.size < 1
       acceptor.accept(Issues::MISSING_INDEX, o)
     end
   end
 
   def check_AssignmentExpression(o)
     case o.operator
     when :'='
       assign(o.left_expr)
       rvalue(o.right_expr)
     when :'+=', :'-='
       acceptor.accept(Issues::APPENDS_DELETES_NO_LONGER_SUPPORTED, o, {:operator => o.operator})
     else
       acceptor.accept(Issues::UNSUPPORTED_OPERATOR, o, {:operator => o.operator})
     end
   end
 
   # Checks that operation with :+> is contained in a ResourceOverride or Collector.
   #
   # Parent of an AttributeOperation can be one of:
   # * CollectExpression
   # * ResourceOverride
   # * ResourceBody (ILLEGAL this is a regular resource expression)
   # * ResourceDefaults (ILLEGAL)
   #
   def check_AttributeOperation(o)
     if o.operator == :'+>'
       # Append operator use is constrained
       parent = o.eContainer
       unless parent.is_a?(Model::CollectExpression) || parent.is_a?(Model::ResourceOverrideExpression)
         acceptor.accept(Issues::ILLEGAL_ATTRIBUTE_APPEND, o, {:name=>o.attribute_name, :parent=>parent})
       end
     end
     rvalue(o.value_expr)
   end
 
   def check_AttributesOperation(o)
     # Append operator use is constrained
     parent = o.eContainer
     parent = parent.eContainer unless parent.nil?
     unless parent.is_a?(Model::ResourceExpression)
       acceptor.accept(Issues::UNSUPPORTED_OPERATOR_IN_CONTEXT, o, :operator=>'* =>')
     end
 
     rvalue(o.expr)
   end
 
   def check_BinaryExpression(o)
     rvalue(o.left_expr)
     rvalue(o.right_expr)
   end
 
   def check_BlockExpression(o)
     o.statements[0..-2].each do |statement|
       if idem(statement)
         acceptor.accept(Issues::IDEM_EXPRESSION_NOT_LAST, statement)
         break # only flag the first
       end
     end
   end
 
   def check_CallNamedFunctionExpression(o)
     case o.functor_expr
     when Puppet::Pops::Model::QualifiedName
       # ok
       nil
     when Puppet::Pops::Model::RenderStringExpression
       # helpful to point out this easy to make Epp error
       acceptor.accept(Issues::ILLEGAL_EPP_PARAMETERS, o)
     else
       acceptor.accept(Issues::ILLEGAL_EXPRESSION, o.functor_expr, {:feature=>'function name', :container => o})
     end
   end
 
   def check_EppExpression(o)
     if o.eContainer.is_a?(Puppet::Pops::Model::LambdaExpression)
       internal_check_no_capture(o.eContainer, o)
     end
   end
 
   def check_MethodCallExpression(o)
     unless o.functor_expr.is_a? Model::QualifiedName
       acceptor.accept(Issues::ILLEGAL_EXPRESSION, o.functor_expr, :feature => 'function name', :container => o)
     end
   end
 
   def check_CaseExpression(o)
     rvalue(o.test)
     # There should only be one LiteralDefault case option value
     # TODO: Implement this check
   end
 
   def check_CaseOption(o)
     o.values.each { |v| rvalue(v) }
   end
 
   def check_CollectExpression(o)
     unless o.type_expr.is_a? Model::QualifiedReference
       acceptor.accept(Issues::ILLEGAL_EXPRESSION, o.type_expr, :feature=> 'type name', :container => o)
     end
 
     # If a collect expression tries to collect exported resources and storeconfigs is not on
     # then it will not work... This was checked in the parser previously. This is a runtime checking
     # thing as opposed to a language thing.
     if acceptor.will_accept?(Issues::RT_NO_STORECONFIGS) && o.query.is_a?(Model::ExportedQuery)
       acceptor.accept(Issues::RT_NO_STORECONFIGS, o)
     end
   end
 
   # Only used for function names, grammar should not be able to produce something faulty, but
   # check anyway if model is created programatically (it will fail in transformation to AST for sure).
   def check_NamedAccessExpression(o)
     name = o.right_expr
     unless name.is_a? Model::QualifiedName
       acceptor.accept(Issues::ILLEGAL_EXPRESSION, name, :feature=> 'function name', :container => o.eContainer)
     end
   end
 
   RESERVED_TYPE_NAMES = {
     'type' => true,
     'any' => true,
     'unit' => true,
     'scalar' => true,
     'boolean' => true,
     'numeric' => true,
     'integer' => true,
     'float' => true,
     'collection' => true,
     'array' => true,
     'hash' => true,
     'tuple' => true,
     'struct' => true,
     'variant' => true,
     'optional' => true,
     'enum' => true,
     'regexp' => true,
     'pattern' => true,
     'runtime' => true,
   }
 
   # for 'class', 'define', and function
   def check_NamedDefinition(o)
     top(o.eContainer, o)
     if o.name !~ Puppet::Pops::Patterns::CLASSREF
       acceptor.accept(Issues::ILLEGAL_DEFINITION_NAME, o, {:name=>o.name})
     end
 
     if RESERVED_TYPE_NAMES[o.name()]
       acceptor.accept(Issues::RESERVED_TYPE_NAME, o, {:name => o.name})
     end
 
     if violator = ends_with_idem(o.body)
       acceptor.accept(Issues::IDEM_NOT_ALLOWED_LAST, violator, {:container => o})
     end
   end
 
   def check_HostClassDefinition(o)
     check_NamedDefinition(o)
     internal_check_no_capture(o)
     internal_check_reserved_params(o)
   end
 
   def check_ResourceTypeDefinition(o)
     check_NamedDefinition(o)
     internal_check_no_capture(o)
     internal_check_reserved_params(o)
   end
 
   def internal_check_capture_last(o)
     accepted_index = o.parameters.size() -1
     o.parameters.each_with_index do |p, index|
       if p.captures_rest && index != accepted_index
         acceptor.accept(Issues::CAPTURES_REST_NOT_LAST, p, {:param_name => p.name})
       end
     end
   end
 
   def internal_check_no_capture(o, container = o)
     o.parameters.each do |p|
       if p.captures_rest
         acceptor.accept(Issues::CAPTURES_REST_NOT_SUPPORTED, p, {:container => container, :param_name => p.name})
       end
     end
   end
 
   RESERVED_PARAMETERS = {
     'name' => true,
     'title' => true,
   }
 
   def internal_check_reserved_params(o)
     o.parameters.each do |p|
       if RESERVED_PARAMETERS[p.name]
         acceptor.accept(Issues::RESERVED_PARAMETER, p, {:container => o, :param_name => p.name})
       end
     end
   end
 
   def check_IfExpression(o)
     rvalue(o.test)
   end
 
   def check_KeyedEntry(o)
     rvalue(o.key)
     rvalue(o.value)
     # In case there are additional things to forbid than non-rvalues
     # acceptor.accept(Issues::ILLEGAL_EXPRESSION, o.key, :feature => 'hash key', :container => o.eContainer)
   end
 
   def check_LambdaExpression(o)
     internal_check_capture_last(o)
   end
 
   def check_LiteralList(o)
     o.values.each {|v| rvalue(v) }
   end
 
+  def check_LiteralFloat(o)
+    migration_checker.report_ambiguous_float(o)
+  end
+
+  def check_LiteralInteger(o)
+    migration_checker.report_ambiguous_integer(o)
+  end
+
   def check_NodeDefinition(o)
     # Check that hostnames are valid hostnames (or regular expressions)
     hostname(o.host_matches, o)
     hostname(o.parent, o, 'parent') unless o.parent.nil?
     top(o.eContainer, o)
     if violator = ends_with_idem(o.body)
       acceptor.accept(Issues::IDEM_NOT_ALLOWED_LAST, violator, {:container => o})
     end
     unless o.parent.nil?
       acceptor.accept(Issues::ILLEGAL_NODE_INHERITANCE, o.parent)
     end
   end
 
   # No checking takes place - all expressions using a QualifiedName need to check. This because the
   # rules are slightly different depending on the container (A variable allows a numeric start, but not
   # other names). This means that (if the lexer/parser so chooses) a QualifiedName
   # can be anything when it represents a Bare Word and evaluates to a String.
   #
   def check_QualifiedName(o)
   end
 
   # Checks that the value is a valid UpperCaseWord (a CLASSREF), and optionally if it contains a hypen.
   # DOH: QualifiedReferences are created with LOWER CASE NAMES at parse time
   def check_QualifiedReference(o)
     # Is this a valid qualified name?
     if o.value !~ Puppet::Pops::Patterns::CLASSREF
       acceptor.accept(Issues::ILLEGAL_CLASSREF, o, {:name=>o.value})
     end
   end
 
   def check_QueryExpression(o)
     query(o.expr) if o.expr  # is optional
   end
 
   def relation_Object(o)
     rvalue(o)
   end
 
   def relation_CollectExpression(o); end
 
   def relation_RelationshipExpression(o); end
 
   def check_Parameter(o)
     if o.name =~ /^(?:0x)?[0-9]+$/
       acceptor.accept(Issues::ILLEGAL_NUMERIC_PARAMETER, o, :name => o.name)
     end
   end
 
   #relationship_side: resource
   #  | resourceref
   #  | collection
   #  | variable
   #  | quotedtext
   #  | selector
   #  | casestatement
   #  | hasharrayaccesses
 
   def check_RelationshipExpression(o)
     relation(o.left_expr)
     relation(o.right_expr)
   end
 
   def check_ResourceExpression(o)
     # The expression for type name cannot be statically checked - this is instead done at runtime
     # to enable better error message of the result of the expression rather than the static instruction.
     # (This can be revised as there are static constructs that are illegal, but require updating many
     # tests that expect the detailed reporting).
   end
 
   def check_ResourceBody(o)
     seenUnfolding = false
     o.operations.each do |ao|
       if ao.is_a?(Puppet::Pops::Model::AttributesOperation)
         if seenUnfolding
           acceptor.accept(Issues::MULTIPLE_ATTRIBUTES_UNFOLD, ao)
         else
           seenUnfolding = true
         end
       end
     end
   end
 
   def check_ResourceDefaultsExpression(o)
     if o.form && o.form != :regular
       acceptor.accept(Issues::NOT_VIRTUALIZEABLE, o)
     end
   end
 
   def check_ResourceOverrideExpression(o)
     if o.form && o.form != :regular
       acceptor.accept(Issues::NOT_VIRTUALIZEABLE, o)
     end
   end
 
   def check_ReservedWord(o)
     acceptor.accept(Issues::RESERVED_WORD, o, :word => o.word)
   end
 
   def check_SelectorExpression(o)
     rvalue(o.left_expr)
   end
 
   def check_SelectorEntry(o)
     rvalue(o.matching_expr)
   end
 
   def check_UnaryExpression(o)
     rvalue(o.expr)
   end
 
   def check_UnlessExpression(o)
     rvalue(o.test)
     # TODO: Unless may not have an else part that is an IfExpression (grammar denies this though)
   end
 
   # Checks that variable is either strictly 0, or a non 0 starting decimal number, or a valid VAR_NAME
   def check_VariableExpression(o)
     # The expression must be a qualified name or an integer
     name_expr = o.expr
     return if name_expr.is_a?(Model::LiteralInteger)
     if !name_expr.is_a?(Model::QualifiedName)
       acceptor.accept(Issues::ILLEGAL_EXPRESSION, o, :feature => 'name', :container => o)
     else
       # name must be either a decimal string value, or a valid NAME
       name = o.expr.value
       if name[0,1] =~ /[0-9]/
         unless name =~ Puppet::Pops::Patterns::NUMERIC_VAR_NAME
           acceptor.accept(Issues::ILLEGAL_NUMERIC_VAR_NAME, o, :name => name)
         end
       else
         unless name =~ Puppet::Pops::Patterns::VAR_NAME
           acceptor.accept(Issues::ILLEGAL_VAR_NAME, o, :name => name)
         end
       end
     end
   end
 
   #--- HOSTNAME CHECKS
 
   # Transforms Array of host matching expressions into a (Ruby) array of AST::HostName
   def hostname_Array(o, semantic, single_feature_name)
     if single_feature_name
       acceptor.accept(Issues::ILLEGAL_EXPRESSION, o, {:feature=>single_feature_name, :container=>semantic})
     end
     o.each {|x| hostname(x, semantic, false) }
   end
 
   def hostname_String(o, semantic, single_feature_name)
     # The 3.x checker only checks for illegal characters - if matching /[^-\w.]/ the name is invalid,
     # but this allows pathological names like "a..b......c", "----"
     # TODO: Investigate if more illegal hostnames should be flagged.
     #
     if o =~ Puppet::Pops::Patterns::ILLEGAL_HOSTNAME_CHARS
       acceptor.accept(Issues::ILLEGAL_HOSTNAME_CHARS, semantic, :hostname => o)
     end
   end
 
   def hostname_LiteralValue(o, semantic, single_feature_name)
     hostname_String(o.value.to_s, o, single_feature_name)
   end
 
   def hostname_ConcatenatedString(o, semantic, single_feature_name)
     # Puppet 3.1. only accepts a concatenated string without interpolated expressions
     if the_expr = o.segments.index {|s| s.is_a?(Model::TextExpression) }
       acceptor.accept(Issues::ILLEGAL_HOSTNAME_INTERPOLATION, o.segments[the_expr].expr)
     elsif o.segments.size() != 1
       # corner case, bad model, concatenation of several plain strings
       acceptor.accept(Issues::ILLEGAL_HOSTNAME_INTERPOLATION, o)
     else
       # corner case, may be ok, but lexer may have replaced with plain string, this is
       # here if it does not
       hostname_String(o.segments[0], o.segments[0], false)
     end
   end
 
   def hostname_QualifiedName(o, semantic, single_feature_name)
     hostname_String(o.value.to_s, o, single_feature_name)
   end
 
   def hostname_QualifiedReference(o, semantic, single_feature_name)
     hostname_String(o.value.to_s, o, single_feature_name)
   end
 
   def hostname_LiteralNumber(o, semantic, single_feature_name)
     # always ok
   end
 
   def hostname_LiteralDefault(o, semantic, single_feature_name)
     # always ok
   end
 
   def hostname_LiteralRegularExpression(o, semantic, single_feature_name)
     # always ok
   end
 
   def hostname_Object(o, semantic, single_feature_name)
     acceptor.accept(Issues::ILLEGAL_EXPRESSION, o, {:feature=> single_feature_name || 'hostname', :container=>semantic})
   end
 
   #---QUERY CHECKS
 
   # Anything not explicitly allowed is flagged as error.
   def query_Object(o)
     acceptor.accept(Issues::ILLEGAL_QUERY_EXPRESSION, o)
   end
 
   # Puppet AST only allows == and !=
   #
   def query_ComparisonExpression(o)
     acceptor.accept(Issues::ILLEGAL_QUERY_EXPRESSION, o) unless [:'==', :'!='].include? o.operator
   end
 
   # Allows AND, OR, and checks if left/right are allowed in query.
   def query_BooleanExpression(o)
     query o.left_expr
     query o.right_expr
   end
 
   def query_ParenthesizedExpression(o)
     query(o.expr)
   end
 
   def query_VariableExpression(o); end
 
   def query_QualifiedName(o); end
 
   def query_LiteralNumber(o); end
 
   def query_LiteralString(o); end
 
   def query_LiteralBoolean(o); end
 
   #---RVALUE CHECKS
 
   # By default, all expressions are reported as being rvalues
   # Implement specific rvalue checks for those that are not.
   #
   def rvalue_Expression(o); end
 
   def rvalue_CollectExpression(o)         ; acceptor.accept(Issues::NOT_RVALUE, o) ; end
 
   def rvalue_Definition(o)                ; acceptor.accept(Issues::NOT_RVALUE, o) ; end
 
   def rvalue_NodeDefinition(o)            ; acceptor.accept(Issues::NOT_RVALUE, o) ; end
 
   def rvalue_UnaryExpression(o)           ; rvalue o.expr                 ; end
 
   #---TOP CHECK
 
   def top_NilClass(o, definition)
     # ok, reached the top, no more parents
   end
 
   def top_Object(o, definition)
     # fail, reached a container that is not top level
     acceptor.accept(Issues::NOT_TOP_LEVEL, definition)
   end
 
   def top_BlockExpression(o, definition)
     # ok, if this is a block representing the body of a class, or is top level
     top o.eContainer, definition
   end
 
   def top_HostClassDefinition(o, definition)
     # ok, stop scanning parents
   end
 
   def top_Program(o, definition)
     # ok
   end
 
   # A LambdaExpression is a BlockExpression, and this method is needed to prevent the polymorph method for BlockExpression
   # to accept a lambda.
   # A lambda can not iteratively create classes, nodes or defines as the lambda does not have a closure.
   #
   def top_LambdaExpression(o, definition)
     # fail, stop scanning parents
     acceptor.accept(Issues::NOT_TOP_LEVEL, definition)
   end
 
   #--IDEM CHECK
   def idem_Object(o)
     false
   end
 
   def idem_Nop(o)
     true
   end
 
   def idem_NilClass(o)
     true
   end
 
   def idem_Literal(o)
     true
   end
 
   def idem_LiteralList(o)
     true
   end
 
   def idem_LiteralHash(o)
     true
   end
 
   def idem_Factory(o)
     idem(o.current)
   end
 
   def idem_AccessExpression(o)
     true
   end
 
   def idem_BinaryExpression(o)
     true
   end
 
   def idem_RelationshipExpression(o)
     # Always side effect
     false
   end
 
   def idem_AssignmentExpression(o)
     # Always side effect
     false
   end
 
   # Handles UnaryMinusExpression, NotExpression, VariableExpression
   def idem_UnaryExpression(o)
     true
   end
 
   # Allow (no-effect parentheses) to be used around a productive expression
   def idem_ParenthesizedExpression(o)
     idem(o.expr)
   end
 
   def idem_RenderExpression(o)
     false
   end
 
   def idem_RenderStringExpression(o)
     false
   end
 
   def idem_BlockExpression(o)
     # productive if there is at least one productive expression
     ! o.statements.any? {|expr| !idem(expr) }
   end
 
   # Returns true even though there may be interpolated expressions that have side effect.
   # Report as idem anyway, as it is very bad design to evaluate an interpolated string for its
   # side effect only.
   def idem_ConcatenatedString(o)
     true
   end
 
   # Heredoc is just a string, but may contain interpolated string (which may have side effects).
   # This is still bad design and should be reported as idem.
   def idem_HeredocExpression(o)
     true
   end
 
   # May technically have side effects inside the Selector, but this is bad design - treat as idem
   def idem_SelectorExpression(o)
     true
   end
 
   def idem_IfExpression(o)
     [o.test, o.then_expr, o.else_expr].all? {|e| idem(e) }
   end
 
   # Case expression is idem, if test, and all options are idem
   def idem_CaseExpression(o)
     return false if !idem(o.test)
     ! o.options.any? {|opt| !idem(opt) }
   end
 
   # An option is idem if values and the then_expression are idem
   def idem_CaseOption(o)
     return false if o.values.any? { |value| !idem(value) }
     idem(o.then_expr)
   end
 
   #--- NON POLYMORPH, NON CHECKING CODE
 
   # Produces string part of something named, or nil if not a QualifiedName or QualifiedReference
   #
   def varname_to_s(o)
     case o
     when Model::QualifiedName
       o.value
     when Model::QualifiedReference
       o.value
     else
       nil
     end
   end
 end
diff --git a/spec/unit/pops/migration_spec.rb b/spec/unit/pops/migration_spec.rb
index cd6133fc8..f1ade8d81 100644
--- a/spec/unit/pops/migration_spec.rb
+++ b/spec/unit/pops/migration_spec.rb
@@ -1,54 +1,75 @@
 require 'spec_helper'
 
 require 'puppet/pops'
 require 'puppet/pops/evaluator/evaluator_impl'
 require 'puppet/loaders'
 require 'puppet_spec/pops'
 require 'puppet_spec/scope'
 require 'puppet/parser/e4_parser_adapter'
 
 describe 'Puppet::Pops::MigrationMigrationChecker' do
   include PuppetSpec::Pops
   include PuppetSpec::Scope
   before(:each) do
     Puppet[:strict_variables] = true
 
     # These must be set since the 3x logic switches some behaviors on these even if the tests explicitly
     # use the 4x parser and evaluator.
     #
     Puppet[:parser] = 'future'
 
     # Puppetx cannot be loaded until the correct parser has been set (injector is turned off otherwise)
     require 'puppetx'
 
     # Tests needs a known configuration of node/scope/compiler since it parses and evaluates
     # snippets as the compiler will evaluate them, butwithout the overhead of compiling a complete
     # catalog for each tested expression.
     #
     @parser  = Puppet::Pops::Parser::EvaluatingParser.new
     @node = Puppet::Node.new('node.example.com')
     @node.environment = Puppet::Node::Environment.create(:testing, [])
     @compiler = Puppet::Parser::Compiler.new(@node)
     @scope = Puppet::Parser::Scope.new(@compiler)
     @scope.source = Puppet::Resource::Type.new(:node, 'node.example.com')
     @scope.parent = @compiler.topscope
   end
 
   let(:scope) { @scope }
+  let(:parser) { @parser}
 
   context "when there is no MigrationChecker in the PuppetContext" do
     it "a null implementation of the MigrationChecker gets created (once per impl that needs one)" do
-      Puppet::Pops::Migration::MigrationChecker.expects(:new).at_least_once
+      migration_checker = Puppet::Pops::Migration::MigrationChecker.new()
+      Puppet::Pops::Migration::MigrationChecker.expects(:new).at_least_once.returns(migration_checker)
       Puppet::Pops::Parser::EvaluatingParser.new.evaluate_string(scope, "1", __FILE__).should == 1
     end
   end
 
   context "when there is a MigrationChecker in the Puppet Context" do
     it "does not create any MigrationChecker instances when parsing and evaluating" do
-      Puppet.override({:migration_checker => Puppet::Pops::Migration::MigrationChecker.new()}, "test-context") do
-        Puppet::Pops::Migration::MigrationChecker.expects(:new).never
+      migration_checker = Puppet::Pops::Migration::MigrationChecker.new()
+      Puppet::Pops::Migration::MigrationChecker.expects(:new).never
+      Puppet.override({:migration_checker => migration_checker}, "test-context") do
         Puppet::Pops::Parser::EvaluatingParser.new.evaluate_string(scope, "1", __FILE__).should == 1
       end
     end
   end
+
+  context "when validating parsed code" do
+    it "is called for each integer" do
+      migration_checker = Puppet::Pops::Migration::MigrationChecker.new()
+      migration_checker.expects(:report_ambiguous_integer).times(3)
+      Puppet.override({:migration_checker => migration_checker}, "migration-context") do
+        parser.evaluate_string(scope, "$a = [1,2,3]", __FILE__)
+      end
+    end
+
+    it "is called for each float" do
+      migration_checker = Puppet::Pops::Migration::MigrationChecker.new()
+      migration_checker.expects(:report_ambiguous_float).times(3)
+      Puppet.override({:migration_checker => migration_checker}, "migration-context") do
+        parser.evaluate_string(scope, "$a = [1.0,2.0,3.1415]", __FILE__)
+      end
+    end
+  end
 end
\ No newline at end of file