Fix indentation of chained dangling selectors.

    foo.
      bar.
        baz

Now indents properly as

    foo.
      bar.
      baz

Fix by treating period as an operator so it is taken into account by
go--continuation-line-indents-p. Period isn't technically a Go
operator, but it can be a dangling operator as far as go-mode is
concerned.

Fixes #346.

Closes: #347 [via git-merge-pr]

Author: muirdm

go-mode.el

@@ -994,23 +994,26 @@ is done."
           indent
         (+ indent (current-indentation))))))
 
-(defconst go--operator-chars "*/%<>&\\^+\\-|=!,"
+(defconst go--operator-chars "*/%<>&\\^+\\-|=!,."
   "Individual characters that appear in operators.
-Comma is included because it is sometimes a dangling operator, so
-needs to be considered by `go--continuation-line-indents-p'")
+Comma and period are included because they can be dangling operators, so
+they need to be considered by `go--continuation-line-indents-p'")
 
 (defun go--operator-precedence (op)
   "Go operator precedence (higher binds tighter).
 
-Comma gets the default 0 precedence which is appropriate because commas
-are loose binding expression separators."
+Comma and period are present because they can be dangling
+operators that affect indentation, although they aren't
+technically operators."
   (cl-case (intern op)
+    (\. 7) ; "." in "foo.bar", binds tightest
     (! 6)
     ((* / % << >> & &^) 5)
     ((+ - | ^) 4)
     ((== != < <= > >=) 3)
     (&& 2)
     (|| 1)
+    (, 0) ; loose binding expression separator
     (t 0)))
 
 (defun go--flow-block-p ()

test/testdata/indentation_tests/dangling_operator.go

@@ -284,6 +284,11 @@ lol` +
 				},
 			}
 
+	foo.
+		bar.
+		baz.
+		qux
+
 	return 123,
 		456
 }