[4638] Cleanup of plurals and inheritance relationships in AST

Changed the grammar so that the following "plural" constructs always
parse as an ASTArray:

- funcvalues
- rvalues
- resourceinstances
- anyparams
- params
- caseopts
- casevalues

And the following "singluar" construct never parses as an ASTArray:

- statement

The previous behavior was for these constructs to parse as a scalar
when they represented a single item and an ASTArray when they
contained zero or multiple items.  ("Statement" could sometimes
represent a single item because a single resource declaration could
represent multiple resources).  This complicated other grammar rules
and caused ambiguous handling of nested arrays.

Also made these changes to the AST class hierarchy:

- ResourceInstance no longer derives from ASTArray.  This relationship
  was not meaningful because a ResourceInstance is a (title,
  parameters) pair, not an array, and it produced complications when
  we wanted to represent an array of ResourceInstance objects.

- Resource no longer derives from ResourceReference.  No significant
  functionality was being inherited and the relationship doesn't make
  sense in an AST context.

- ResourceOverride no longer derives from Resource.  No significant
  functionality was being inherited and the relationship doesn't make
  sense in an AST context.

- Resource can now represent a compound resource instance such as
  "notify { foo: ; bar: }".  This saves the parser from having to
  use represent a statement as an array of objects.

- ASTArray's evaluate method never flattens out arrays of arrays.

1 files changed, 12 insertions, 24 deletions

diff --git a/lib/puppet/parser/ast/caseopt.rb b/lib/puppet/parser/ast/caseopt.rb
index 4e296e82f..db4c2b024 100644
--- a/lib/puppet/parser/ast/caseopt.rb
+++ b/lib/puppet/parser/ast/caseopt.rb
@@ -18,16 +18,12 @@ class Puppet::Parser::AST
       # Cache the @default value.
       return @default if defined?(@default)
 
-      if @value.is_a?(AST::ASTArray)
-        @value.each { |subval|
-          if subval.is_a?(AST::Default)
-            @default = true
-            break
-          end
-        }
-      else
-        @default = true if @value.is_a?(AST::Default)
-      end
+      @value.each { |subval|
+        if subval.is_a?(AST::Default)
+          @default = true
+          break
+        end
+      }
 
       @default ||= false
 
@@ -36,23 +32,15 @@ class Puppet::Parser::AST
 
     # You can specify a list of values; return each in turn.
     def eachvalue(scope)
-      if @value.is_a?(AST::ASTArray)
-        @value.each { |subval|
-          yield subval.safeevaluate(scope)
-        }
-      else
-        yield @value.safeevaluate(scope)
-      end
+      @value.each { |subval|
+        yield subval.safeevaluate(scope)
+      }
     end
 
     def eachopt
-      if @value.is_a?(AST::ASTArray)
-        @value.each { |subval|
-          yield subval
-        }
-      else
-        yield @value
-      end
+      @value.each { |subval|
+        yield subval
+      }
     end
 
     # Evaluate the actual statements; this only gets called if