cmd/compile: fix nodedump output for types of nodes

The Dbg dumping of complex types was broken, because (I think) of a
recent change to handle recursive types correctly. Before this fix,
the Dump output of a closure node (where the last thing on the line is
the type of the node) was:

.   .   CLOSURE l(8) esc(h) tc(1) FUNC-@0

after this change it is:

.   .   CLOSURE l(8) esc(h) tc(1) FUNC-func(int) int

The problem is that that the 'mode == Fdbg' code was immediately
aborting the descent into tconv2, since it was calling down with the
same node that was just entered into the hash table.

Change-Id: Iee106b967cea1856dd92d4350681401dd34a23b3
Reviewed-on: https://go-review.googlesource.com/c/go/+/264025
Trust: Dan Scales <[email protected]>
Reviewed-by: Keith Randall <[email protected]>

Author: danscales

src/cmd/compile/internal/gc/fmt.go

@@ -792,6 +792,13 @@ func tconv2(b *bytes.Buffer, t *types.Type, flag FmtFlag, mode fmtMode, visited
 		return
 	}
 
+	if mode == FDbg {
+		b.WriteString(t.Etype.String())
+		b.WriteByte('-')
+		tconv2(b, t, flag, FErr, visited)
+		return
+	}
+
 	// At this point, we might call tconv2 recursively. Add the current type to the visited list so we don't
 	// try to print it recursively.
 	// We record the offset in the result buffer where the type's text starts. This offset serves as a reference
@@ -805,12 +812,6 @@ func tconv2(b *bytes.Buffer, t *types.Type, flag FmtFlag, mode fmtMode, visited
 	visited[t] = b.Len()
 	defer delete(visited, t)
 
-	if mode == FDbg {
-		b.WriteString(t.Etype.String())
-		b.WriteByte('-')
-		tconv2(b, t, flag, FErr, visited)
-		return
-	}
 	switch t.Etype {
 	case TPTR:
 		b.WriteByte('*')