cmd/compile/internal/types2: don't print instance markers for type hashes

Since we know whether we are printing a type string used as
instance hash, don't print instance markers, so that we don't
need to remove them afterwards either.

Change-Id: Ib01627b6da989ef89d51e734810a3377eb466925
Reviewed-on: https://go-review.googlesource.com/c/go/+/345891
Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

diff --git a/src/cmd/compile/internal/types2/subst.go b/src/cmd/compile/internal/types2/subst.go
index f4891df664abf77374ff453d437f22e0141f0171..9a4db6fddb64e408db2bf3a9118ced3e591763d9 100644 (file)
--- a/src/cmd/compile/internal/types2/subst.go
+++ b/src/cmd/compile/internal/types2/subst.go
@@ -256,28 +256,23 @@ func (subst *subster) typ(typ Type) Type {
 var instanceHashing = 0
 
 func instantiatedHash(typ *Named, targs []Type) string {
+       var buf bytes.Buffer
+
        assert(instanceHashing == 0)
        instanceHashing++
-       var buf bytes.Buffer
        w := newTypeWriter(&buf, nil)
        w.typeName(typ.obj)
        w.typeList(targs)
        instanceHashing--
 
-       // With respect to the represented type, whether a
-       // type is fully expanded or stored as instance
-       // does not matter - they are the same types.
-       // Remove the instanceMarkers printed for instances.
-       res := buf.Bytes()
-       i := 0
-       for _, b := range res {
-               if b != instanceMarker {
-                       res[i] = b
-                       i++
+       if debug {
+               // there should be no instance markers in type hashes
+               for _, b := range buf.Bytes() {
+                       assert(b != instanceMarker)
                }
        }
 
-       return string(res[:i])
+       return buf.String()
 }
 
 // typOrNil is like typ but if the argument is nil it is replaced with Typ[Invalid].

diff --git a/src/cmd/compile/internal/types2/typestring.go b/src/cmd/compile/internal/types2/typestring.go
index d02f38a6ac49f5f890e0dee7e51e58b20cb01d3e..3b9981089e178f48cce1f29cf4c6228e706c74f2 100644 (file)
--- a/src/cmd/compile/internal/types2/typestring.go
+++ b/src/cmd/compile/internal/types2/typestring.go
@@ -203,7 +203,11 @@ func (w *typeWriter) typ(typ Type) {
                }
 
        case *Named:
-               if t.instPos != nil {
+               // Instance markers indicate unexpanded instantiated
+               // types. Write them to aid debugging, but don't write
+               // them when we need an instance hash: whether a type
+               // is fully expanded or not doesn't matter for identity.
+               if instanceHashing == 0 && t.instPos != nil {
                        w.byte(instanceMarker)
                }
                w.typeName(t.obj)