go/types: fix scope printing (debugging support)

Printing of scopes was horribly wrong: If a scope contained
no object declarations, it would abort printing even if the
scope had children scopes. Also, the line breaks were not
inserted consistently. The actual test case (ExampleScope)
was incorrect as well.

Fixed and simplified printing, and adjusted example which
tests the printing output.

Change-Id: If21c1d4ad71b15a517d4a54da16de5e6228eb4b5
Reviewed-on: https://go-review.googlesource.com/135115
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Alan Donovan <adonovan@google.com>

src/go/types/example_test.go

@@ -51,6 +51,7 @@ type Celsius float64
 func (c Celsius) String() string { return fmt.Sprintf("%g°C", c) }
 func FToC(f float64) Celsius { return Celsius(f - 32 / 9 * 5) }
 const Boiling Celsius = 100
+func Unused() { {}; {{ var x int; _ = x }} } // make sure empty block scopes get printed
 `},
 	} {
 		f, err := parser.ParseFile(fset, file.name, file.input, 0)
@@ -81,23 +82,33 @@ const Boiling Celsius = 100
 	// .  const temperature.Boiling temperature.Celsius
 	// .  type temperature.Celsius float64
 	// .  func temperature.FToC(f float64) temperature.Celsius
+	// .  func temperature.Unused()
 	// .  func temperature.main()
-	//
 	// .  main.go scope {
 	// .  .  package fmt
-	//
 	// .  .  function scope {
 	// .  .  .  var freezing temperature.Celsius
-	// .  .  }.  }
+	// .  .  }
+	// .  }
 	// .  celsius.go scope {
 	// .  .  package fmt
-	//
 	// .  .  function scope {
 	// .  .  .  var c temperature.Celsius
 	// .  .  }
 	// .  .  function scope {
 	// .  .  .  var f float64
-	// .  .  }.  }}
+	// .  .  }
+	// .  .  function scope {
+	// .  .  .  block scope {
+	// .  .  .  }
+	// .  .  .  block scope {
+	// .  .  .  .  block scope {
+	// .  .  .  .  .  var x int
+	// .  .  .  .  }
+	// .  .  .  }
+	// .  .  }
+	// .  }
+	// }
 }
 
 // ExampleMethodSet prints the method sets of various types.

src/go/types/scope.go

@@ -161,13 +161,8 @@ func (s *Scope) WriteTo(w io.Writer, n int, recurse bool) {
 	const ind = ".  "
 	indn := strings.Repeat(ind, n)
 
-	fmt.Fprintf(w, "%s%s scope %p {", indn, s.comment, s)
-	if len(s.elems) == 0 {
-		fmt.Fprintf(w, "}\n")
-		return
-	}
+	fmt.Fprintf(w, "%s%s scope %p {\n", indn, s.comment, s)
 
-	fmt.Fprintln(w)
 	indn1 := indn + ind
 	for _, name := range s.Names() {
 		fmt.Fprintf(w, "%s%s\n", indn1, s.elems[name])
@@ -175,12 +170,11 @@ func (s *Scope) WriteTo(w io.Writer, n int, recurse bool) {
 
 	if recurse {
 		for _, s := range s.children {
-			fmt.Fprintln(w)
 			s.WriteTo(w, n+1, recurse)
 		}
 	}
 
-	fmt.Fprintf(w, "%s}", indn)
+	fmt.Fprintf(w, "%s}\n", indn)
 }
 
 // String returns a string representation of the scope, for debugging.