Correct some of the terminology surrounding the "default constructor."

A constructor without a name is an "unnamed" constructor. A class which
has no constructors explicitly specified implicitly has one "default
constructor". See from the spec:

> Iff no constructor is specified for a class _C_, it implicitly has a
> default constructor `C(): super() {}`, unless _C_ is the built-in
> class `Object`.

This is the singular reference in the spec to this "default
constructor." There is text which refers to the implicit
superinitializer which refers to the superclass's unnamed constructor
which must have zero arguments:

> If no superinitializer is provided, an implicit superinitializer of
> the form `super()` is added at the end of _k_'s initializer list,
> unless the enclosing class is class `Object`.

Change-Id: I3202c3923d2c561d40c2251c1b13ea4fde8bda48
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/208865
Reviewed-by: Brian Wilkerson <[email protected]>
Reviewed-by: Konstantin Shcheglov <[email protected]>
Commit-Queue: Samuel Rawlins <[email protected]>

Author: srawlins

pkg/analyzer/lib/src/error/codes.dart

@@ -2871,7 +2871,7 @@ class CompileTimeErrorCode extends AnalyzerErrorCode {
    */
   static const CompileTimeErrorCode CONST_WITH_UNDEFINED_CONSTRUCTOR_DEFAULT =
       CompileTimeErrorCode('CONST_WITH_UNDEFINED_CONSTRUCTOR_DEFAULT',
-          "The class '{0}' doesn't have a default constant constructor.",
+          "The class '{0}' doesn't have an unnamed constant constructor.",
           correction: "Try calling a different constructor.");
 
   static const CompileTimeErrorCode CONTINUE_LABEL_ON_SWITCH =
@@ -3227,7 +3227,7 @@ class CompileTimeErrorCode extends AnalyzerErrorCode {
   static const CompileTimeErrorCode DUPLICATE_CONSTRUCTOR_DEFAULT =
       CompileTimeErrorCode(
     'DUPLICATE_CONSTRUCTOR',
-    "The default constructor is already defined.",
+    "The unnamed constructor is already defined.",
     correction: "Try giving one of the constructors a name.",
     hasPublishedDocs: true,
     uniqueName: 'DUPLICATE_CONSTRUCTOR_DEFAULT',
@@ -8848,7 +8848,7 @@ class CompileTimeErrorCode extends AnalyzerErrorCode {
   // ```
   static const CompileTimeErrorCode NEW_WITH_UNDEFINED_CONSTRUCTOR_DEFAULT =
       CompileTimeErrorCode('NEW_WITH_UNDEFINED_CONSTRUCTOR_DEFAULT',
-          "The class '{0}' doesn't have a default constructor.",
+          "The class '{0}' doesn't have an unnamed constructor.",
           correction:
               "Try using one of the named constructors defined in '{0}'.",
           hasPublishedDocs: true);
@@ -9955,8 +9955,8 @@ class CompileTimeErrorCode extends AnalyzerErrorCode {
   static const CompileTimeErrorCode NON_GENERATIVE_IMPLICIT_CONSTRUCTOR =
       CompileTimeErrorCode(
           'NON_GENERATIVE_IMPLICIT_CONSTRUCTOR',
-          "The default constructor of superclass '{0}' (called by the implicit "
-              "default constructor of '{1}') must be a generative constructor, "
+          "The unnamed constructor of superclass '{0}' (called by the default "
+              "constructor of '{1}') must be a generative constructor, "
               "but factory found.",
           correction: "Try adding an explicit constructor that has a different "
               "superinitializer or changing the superclass constructor '{2}' "

pkg/analyzer/tool/diagnostics/diagnostics.md

@@ -3352,7 +3352,7 @@ class F {}
 
 _The constructor with name '{0}' is already defined._
 
-_The default constructor is already defined._
+_The unnamed constructor is already defined._
 
 #### Description
 
@@ -8738,7 +8738,7 @@ name: example
 
 ### new_with_undefined_constructor_default
 
-_The class '{0}' doesn't have a default constructor._
+_The class '{0}' doesn't have an unnamed constructor._
 
 #### Description