Adds basic support for class functions and methods. (#1057)

* adding methods to the ast

* pre commit stuff?

* implementation of class functions

* implemented methods

* some cleanup

* more cleanup

* add newlines in test programs

* pre-commit fixups

* added include of return_term.h

* a test of a method calling another method

* replacing Member with Declaration

* removing the member.h etc files

* clarify a type annotation

* update uses of FunctionDeclaration

* remove ReturnTarget, no longer needed

* more cleanup

* more cleanup

* yet more cleanup, playing with pre-commit

* did a pre-commit run --all-files

* fixed const issue

* remove comment

* checking dependencies in BUILD files and headers

* pre-commit working now

* refactor NominalClassType to just hold a pointer to the class declaration

* remove Member from rtti

* responding to Geoffreys review

* change field_types to a non-member function

executable_semantics/ast/BUILD

@@ -77,8 +77,8 @@ cc_library(
     ],
     deps = [
         ":ast_node",
-        ":member",
         ":pattern",
+        ":return_term",
         ":source_location",
         ":statement",
         ":static_scope",
@@ -89,6 +89,18 @@ cc_library(
     ],
 )
 
+cc_library(
+    name = "return_term",
+    hdrs = ["return_term.h"],
+    deps = [
+        ":source_location",
+        "//common:check",
+        "//common:ostream",
+        "//executable_semantics/common:nonnull",
+        "@llvm-project//llvm:Support",
+    ],
+)
+
 cc_library(
     name = "expression",
     srcs = ["expression.cpp"],
@@ -119,20 +131,6 @@ cc_test(
     ],
 )
 
-cc_library(
-    name = "member",
-    srcs = ["member.cpp"],
-    hdrs = ["member.h"],
-    deps = [
-        ":expression",
-        ":pattern",
-        ":source_location",
-        "//common:ostream",
-        "//executable_semantics/common:arena",
-        "@llvm-project//llvm:Support",
-    ],
-)
-
 cc_library(
     name = "library_name",
     hdrs = ["library_name.h"],
@@ -186,7 +184,6 @@ cc_library(
         ":source_location",
         ":value_category",
         "//common:check",
-        "//executable_semantics/common:arena",
         "//executable_semantics/common:error",
         "//executable_semantics/common:nonnull",
     ],
@@ -209,6 +206,7 @@ cc_library(
         ":ast_node",
         ":expression",
         ":pattern",
+        ":return_term",
         ":source_location",
         ":static_scope",
         ":value_category",