Adjust examples declaring non-nullable positional optional parameters with no default

Author: eernstg

specification/dartLangSpec.tex

@@ -3469,7 +3469,7 @@ \subsubsection{The Method \code{noSuchMethod}}
   in order to correctly override \code{noSuchMethod} in \code{Object}.
   For instance, it can have signature
   \code{noSuchMethod(Invocation i)} or
-  \code{noSuchMethod(Object i, [String s = ''])},
+  \code{noSuchMethod(Object i, [String? s])},
   but not
   \code{noSuchMethod(Invocation i, String s)}.
   This implies that the situation where \code{noSuchMethod} is invoked
@@ -4242,7 +4242,7 @@ \subsubsection{Generative Constructors}
 
 \begin{dartCode}
 class A \{
-  int x;
+  int? x;
   A([this.x]);
 \}
 \end{dartCode}
@@ -4253,8 +4253,8 @@ \subsubsection{Generative Constructors}
 
 \begin{dartCode}
 class A \{
-  int x;
-  A([int x]): this.x = x;
+  int? x;
+  A([int? x]): this.x = x;
 \}
 \end{dartCode}
 
@@ -15962,7 +15962,7 @@ \subsubsection{Generic Method Instantiation}
 \}
 \\
 \CLASS{} B \EXTENDS{} /*\,or\,\,\IMPLEMENTS\,*/ A \{
-  X fi<X \EXTENDS{} num>(X x, [List<X> xs]) => x;
+  X fi<X \EXTENDS{} num>(X x, [List<X>? xs]) => x;
 \}
 \\
 \VOID{} main() \{
@@ -15971,9 +15971,9 @@ \subsubsection{Generic Method Instantiation}
 \}
 \end{dartCode}
 
-\noindent
+\commentary{%
   The function object that \code{f} is bound to at the end of \code{main}
-  has dynamic type \code{int\,\,\FUNCTION(int,\,[List<int>])},
+  has dynamic type \code{int\,\,\FUNCTION(int,\,[List<int>?])},
   and it is obtained by implicitly
   ``passing the actual type argument \code{int}''
   to the denoted generic instance method,