Added compile-time errors for supertypes: Type alias missing, and more.

R=lrn@google.com

Review-Url: https://codereview.chromium.org/2585723002 .

docs/language/dartLangSpec.tex

@@ -1781,9 +1781,8 @@ It is a compile-time error to specify an \EXTENDS{} clause for class \code{Objec
 The scope of the \EXTENDS{} and \WITH{} clauses of a class $C$ is the type-parameter scope of $C$.
 
 \LMHash{}
-%It is a compile-time error if  the \EXTENDS{} clause of a class $C$ includes a type expression that does not denote a class available in the lexical scope of $C$.
-It is a compile-time error if  the \EXTENDS{} clause of a class $C$ specifies an enumerated type (\ref{enums}), a malformed  type or a deferred type (\ref{staticTypes}) as a superclass.
-% too strict? Do we e want extends List<Undeclared> to work as List<dynamic>?
+It is a compile-time error if the \EXTENDS{} clause of a class $C$ specifies a type variable (\ref{generics}), a type alias (\ref{typedef}), an enumerated type (\ref{enums}), a malformed type, or a deferred type (\ref{staticTypes}) as a superclass.
+It is a compile-time error if the \EXTENDS{} clause of a class $C$ specifies type \DYNAMIC{} as a superinterface.
 
 \commentary{ The type parameters of a generic class are available in the lexical scope of the superclass clause, potentially shadowing classes in the surrounding scope. The following code is therefore illegal and should cause a compile-time error:
 }
@@ -1917,7 +1916,9 @@ A class has a set of direct superinterfaces. This set includes the interface of
 The scope of the \IMPLEMENTS{} clause of a class $C$ is the type-parameter scope of $C$.
 
 \LMHash{}
-It is a compile-time error if  the \IMPLEMENTS{}  clause of a class $C$ specifies a type variable as a superinterface. It is a compile-time error if  the  \IMPLEMENTS{} clause of a class $C$ specifies an enumerated type (\ref{enums}),  a malformed type or deferred type (\ref{staticTypes}) as a superinterface.  It is a compile-time error if the \IMPLEMENTS{} clause of a class $C$ specifies type \DYNAMIC{} as a superinterface. It is a compile-time error if  the  \IMPLEMENTS{} clause of a class $C$ specifies  a type $T$ as a superinterface more than once.
+It is a compile-time error if the \IMPLEMENTS{} clause of a class $C$ specifies a type variable (\ref{generics}), a type alias (\ref{typedef}), an enumerated type (\ref{enums}), a malformed type, or a deferred type (\ref{staticTypes}) as a superinterface.
+It is a compile-time error if the \IMPLEMENTS{} clause of a class $C$ specifies type \DYNAMIC{} as a superinterface.
+It is a compile-time error if the \IMPLEMENTS{} clause of a class $C$ specifies a type $T$ as a superinterface more than once.
 It is a compile-time error if the superclass of a class $C$ is specified as a superinterface of $C$.
 
 \rationale{
@@ -2090,8 +2091,10 @@ The restriction on constructors simplifies the construction of mixin application
 \LMLabel{mixinApplication}
 
 \LMHash{}
-A mixin may be applied to a superclass, yielding a new class. Mixin application occurs when a mixin is mixed into a class declaration via its \WITH{} clause.  The mixin application may be used to extend a class per section (\ref{classes}); alternately, a class may be defined as a mixin application as described in this section.   It is a compile-time error if the \WITH{} clause of a mixin application $C$ includes a deferred type expression.
-
+A mixin may be applied to a superclass, yielding a new class.
+Mixin application occurs when a mixin is mixed into a class declaration via its \WITH{} clause.
+The mixin application may be used to extend a class per section (\ref{classes}); alternately, a class may be defined as a mixin application as described in this section.
+It is a compile-time error if the \WITH{} clause of a mixin application $C$ includes a type variable (\ref{generics}), a type alias (\ref{typedef}), an enumerated type (\ref{enums}), a malformed type, or a deferred type (\ref{staticTypes}).
 
 \begin{grammar}
 {\bf  mixinApplicationClass:}