cmd/compile/internal/types2: export TypeHash, return value without blanks

Change the typeWriter to produce blank-free hashes where easily possible
if used as a type hasher, and replace remaining blanks with '#' is needed.

Exported Environment.TypeHash for use by the compiler.

Change-Id: Icbd364c207f9c139a7a1844bb695512a0c56a4e4
Reviewed-on: https://go-review.googlesource.com/c/go/+/349990
Trust: Robert Griesemer <gri@golang.org>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

5 files changed, 41 insertions, 20 deletions

diff --git a/src/cmd/compile/internal/types2/environment.go b/src/cmd/compile/internal/types2/environment.go
index 816139bbb4..5ef8855a1b 100644
--- a/src/cmd/compile/internal/types2/environment.go
+++ b/src/cmd/compile/internal/types2/environment.go
@@ -5,6 +5,7 @@ package types2
 
 import (
 	"bytes"
+	"strings"
 	"sync"
 )
 
@@ -28,11 +29,11 @@ func NewEnvironment() *Environment {
 	}
 }
 
-// typeHash returns a string representation of typ, which can be used as an exact
+// TypeHash returns a string representation of typ, which can be used as an exact
 // type hash: types that are identical produce identical string representations.
 // If typ is a *Named type and targs is not empty, typ is printed as if it were
-// instantiated with targs.
-func (env *Environment) typeHash(typ Type, targs []Type) string {
+// instantiated with targs. The result is guaranteed to not contain blanks (" ").
+func (env *Environment) TypeHash(typ Type, targs []Type) string {
 	assert(env != nil)
 	assert(typ != nil)
 	var buf bytes.Buffer
@@ -56,7 +57,7 @@ func (env *Environment) typeHash(typ Type, targs []Type) string {
 		}
 	}
 
-	return buf.String()
+	return strings.Replace(buf.String(), " ", "#", -1) // ReplaceAll is not available in Go1.4
 }
 
 // typeForHash returns the recorded type for the type hash h, if it exists.
diff --git a/src/cmd/compile/internal/types2/instantiate.go b/src/cmd/compile/internal/types2/instantiate.go
index 469ceea5c4..fdb87e75f6 100644
--- a/src/cmd/compile/internal/types2/instantiate.go
+++ b/src/cmd/compile/internal/types2/instantiate.go
@@ -108,7 +108,7 @@ func (check *Checker) instance(pos syntax.Pos, typ Type, targs []Type, env *Envi
 	case *Named:
 		var h string
 		if env != nil {
-			h = env.typeHash(t, targs)
+			h = env.TypeHash(t, targs)
 			// typ may already have been instantiated with identical type arguments. In
 			// that case, re-use the existing instance.
 			if named := env.typeForHash(h, nil); named != nil {
diff --git a/src/cmd/compile/internal/types2/named.go b/src/cmd/compile/internal/types2/named.go
index 99410aedfb..46487d1cae 100644
--- a/src/cmd/compile/internal/types2/named.go
+++ b/src/cmd/compile/internal/types2/named.go
@@ -262,7 +262,7 @@ func (n *Named) expand(env *Environment) *Named {
 					// instance in the process of expansion.
 					env = NewEnvironment()
 				}
-				h := env.typeHash(n.orig, n.targs.list())
+				h := env.TypeHash(n.orig, n.targs.list())
 				// add the instance to the environment to avoid infinite recursion.
 				// addInstance may return a different, existing instance, but we
 				// shouldn't return that instance from expand.
diff --git a/src/cmd/compile/internal/types2/subst.go b/src/cmd/compile/internal/types2/subst.go
index 4627dd3c5b..8d96494af0 100644
--- a/src/cmd/compile/internal/types2/subst.go
+++ b/src/cmd/compile/internal/types2/subst.go
@@ -211,7 +211,7 @@ func (subst *subster) typ(typ Type) Type {
 		}
 
 		// before creating a new named type, check if we have this one already
-		h := subst.env.typeHash(t.orig, newTArgs)
+		h := subst.env.TypeHash(t.orig, newTArgs)
 		dump(">>> new type hash: %s", h)
 		if named := subst.env.typeForHash(h, nil); named != nil {
 			dump(">>> found %s", named)
diff --git a/src/cmd/compile/internal/types2/typestring.go b/src/cmd/compile/internal/types2/typestring.go
index 39ba278d53..71da37c3a1 100644
--- a/src/cmd/compile/internal/types2/typestring.go
+++ b/src/cmd/compile/internal/types2/typestring.go
@@ -8,7 +8,6 @@ package types2
 
 import (
 	"bytes"
-	"fmt"
 	"strconv"
 	"unicode/utf8"
 )
@@ -83,14 +82,29 @@ func newTypeHasher(buf *bytes.Buffer, env *Environment) *typeWriter {
 	return &typeWriter{buf, make(map[Type]bool), nil, env}
 }
 
-func (w *typeWriter) byte(b byte)                               { w.buf.WriteByte(b) }
-func (w *typeWriter) string(s string)                           { w.buf.WriteString(s) }
-func (w *typeWriter) writef(format string, args ...interface{}) { fmt.Fprintf(w.buf, format, args...) }
+func (w *typeWriter) byte(b byte) {
+	if w.env != nil {
+		if b == ' ' {
+			b = '#'
+		}
+		w.buf.WriteByte(b)
+		return
+	}
+	w.buf.WriteByte(b)
+	if b == ',' || b == ';' {
+		w.buf.WriteByte(' ')
+	}
+}
+
+func (w *typeWriter) string(s string) {
+	w.buf.WriteString(s)
+}
+
 func (w *typeWriter) error(msg string) {
 	if w.env != nil {
 		panic(msg)
 	}
-	w.string("<" + msg + ">")
+	w.buf.WriteString("<" + msg + ">")
 }
 
 func (w *typeWriter) typ(typ Type) {
@@ -117,7 +131,9 @@ func (w *typeWriter) typ(typ Type) {
 		w.string(t.name)
 
 	case *Array:
-		w.writef("[%d]", t.len)
+		w.byte('[')
+		w.string(strconv.FormatInt(t.len, 10))
+		w.byte(']')
 		w.typ(t.elem)
 
 	case *Slice:
@@ -128,7 +144,7 @@ func (w *typeWriter) typ(typ Type) {
 		w.string("struct{")
 		for i, f := range t.fields {
 			if i > 0 {
-				w.string("; ")
+				w.byte(';')
 			}
 			// This doesn't do the right thing for embedded type
 			// aliases where we should print the alias name, not
@@ -139,7 +155,11 @@ func (w *typeWriter) typ(typ Type) {
 			}
 			w.typ(f.typ)
 			if tag := t.Tag(i); tag != "" {
-				w.writef(" %q", tag)
+				w.byte(' ')
+				// TODO(gri) If tag contains blanks, replacing them with '#'
+				//           in Environment.TypeHash may produce another tag
+				//           accidentally.
+				w.string(strconv.Quote(tag))
 			}
 		}
 		w.byte('}')
@@ -177,7 +197,7 @@ func (w *typeWriter) typ(typ Type) {
 		first := true
 		for _, m := range t.methods {
 			if !first {
-				w.string("; ")
+				w.byte(';')
 			}
 			first = false
 			w.string(m.name)
@@ -185,7 +205,7 @@ func (w *typeWriter) typ(typ Type) {
 		}
 		for _, typ := range t.embeddeds {
 			if !first {
-				w.string("; ")
+				w.byte(';')
 			}
 			first = false
 			w.typ(typ)
@@ -279,7 +299,7 @@ func (w *typeWriter) typeList(list []Type) {
 	w.byte('[')
 	for i, typ := range list {
 		if i > 0 {
-			w.string(", ")
+			w.byte(',')
 		}
 		w.typ(typ)
 	}
@@ -303,7 +323,7 @@ func (w *typeWriter) tParamList(list []*TypeParam) {
 				w.byte(' ')
 				w.typ(prev)
 			}
-			w.string(", ")
+			w.byte(',')
 		}
 		prev = tpar.bound
 		w.typ(tpar)
@@ -327,7 +347,7 @@ func (w *typeWriter) tuple(tup *Tuple, variadic bool) {
 	if tup != nil {
 		for i, v := range tup.vars {
 			if i > 0 {
-				w.string(", ")
+				w.byte(',')
 			}
 			// parameter names are ignored for type identity and thus type hashes
 			if w.env == nil && v.name != "" {