Add InternalMethod#getOriginalName() and improve documentation

Author: eregon

src/main/java/org/truffleruby/core/MainNodes.java

@@ -73,7 +73,7 @@ protected Object mainUsing(Frame callerFrame, Object self, Object[] rubyArgs, Ro
 
         @TruffleBoundary
         private boolean isCalledFromTopLevel(InternalMethod callerMethod) {
-            final String name = callerMethod.getSharedMethodInfo().getOriginalName();
+            final String name = callerMethod.getOriginalName();
             return name.equals("<main>") || name.startsWith("<top ");
         }
     }

src/main/java/org/truffleruby/core/method/UnboundMethodNodes.java

@@ -153,11 +153,9 @@ public abstract static class OriginalNameNode extends CoreMethodArrayArgumentsNo
         @Specialization
         protected RubySymbol originalName(RubyUnboundMethod unboundMethod,
                 @Cached ToSymbolNode toSymbolNode) {
-            String originalName = unboundMethod.method.getSharedMethodInfo().getOriginalName();
-
+            String originalName = unboundMethod.method.getOriginalName();
             return toSymbolNode.execute(originalName);
         }
-
     }
 
     @CoreMethod(names = "owner")

src/main/java/org/truffleruby/language/methods/InternalMethod.java

@@ -194,6 +194,10 @@ public String getName() {
         return name;
     }
 
+    public String getOriginalName() {
+        return sharedMethodInfo.getOriginalName();
+    }
+
     public Visibility getVisibility() {
         return visibility;
     }

src/main/java/org/truffleruby/language/methods/SharedMethodInfo.java

@@ -24,8 +24,10 @@
 import org.truffleruby.parser.OpenModule;
 import org.truffleruby.parser.ParserContext;
 
-/** {@link InternalMethod} objects are copied as properties such as visibility are changed. {@link SharedMethodInfo}
- * stores the state that does not change, such as where the method was defined. */
+/** SharedMethodInfo represents static information from the parser for either a method definition or a block like its
+ * name, SourceSection, etc. Such information is always "original" since it comes from the source as opposed to
+ * "aliased" (e.g. the aliased name of a method). In contrast, {@link InternalMethod} are runtime objects containing
+ * properties that change for a method. */
 public final class SharedMethodInfo {
 
     private final SourceSection sourceSection;
@@ -150,6 +152,7 @@ public static boolean isModuleBody(String name) {
         }
     }
 
+    /** See {@link #originalName} */
     public String getOriginalName() {
         return originalName;
     }