go/types: move typeHash to environment.go

This is a pure code move, with no other changes.

Change-Id: Id31f1f960d3208dc614556de89bf39b7ca77df3a
Reviewed-on: https://go-review.googlesource.com/c/go/+/347560
Trust: Robert Findley <rfindley@google.com>
Run-TryBot: Robert Findley <rfindley@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

src/go/types/environment.go

@@ -4,7 +4,10 @@
 
 package types
 
-import "sync"
+import (
+	"bytes"
+	"sync"
+)
 
 // An Environment is an opaque type checking environment. It may be used to
 // share identical type instances across type-checked packages or calls to
@@ -26,7 +29,36 @@ func NewEnvironment() *Environment {
 	}
 }
 
-// TODO(rfindley): move Environment.typeHash here.
+// 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 {
+	assert(env != nil)
+	assert(typ != nil)
+	var buf bytes.Buffer
+
+	h := newTypeHasher(&buf, env)
+	if named, _ := typ.(*Named); named != nil && len(targs) > 0 {
+		// Don't use WriteType because we need to use the provided targs
+		// and not any targs that might already be with the *Named type.
+		h.typePrefix(named)
+		h.typeName(named.obj)
+		h.typeList(targs)
+	} else {
+		assert(targs == nil)
+		h.typ(typ)
+	}
+
+	if debug {
+		// there should be no instance markers in type hashes
+		for _, b := range buf.Bytes() {
+			assert(b != instanceMarker)
+		}
+	}
+
+	return buf.String()
+}
 
 // typeForHash returns the recorded type for the type hash h, if it exists.
 // If no type exists for h and n is non-nil, n is recorded for h.

src/go/types/subst.go

@@ -6,10 +6,7 @@
 
 package types
 
-import (
+import "go/token"
-	"bytes"
-	"go/token"
-)
 
 // TODO(rFindley) decide error codes for the errors in this file, and check
 //                if error spans can be improved
@@ -256,37 +253,6 @@ func (subst *subster) typ(typ Type) Type {
 	return typ
 }
 
-// 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 {
-	assert(env != nil)
-	assert(typ != nil)
-	var buf bytes.Buffer
-
-	h := newTypeHasher(&buf, env)
-	if named, _ := typ.(*Named); named != nil && len(targs) > 0 {
-		// Don't use WriteType because we need to use the provided targs
-		// and not any targs that might already be with the *Named type.
-		h.typePrefix(named)
-		h.typeName(named.obj)
-		h.typeList(targs)
-	} else {
-		assert(targs == nil)
-		h.typ(typ)
-	}
-
-	if debug {
-		// there should be no instance markers in type hashes
-		for _, b := range buf.Bytes() {
-			assert(b != instanceMarker)
-		}
-	}
-
-	return buf.String()
-}
-
 // typOrNil is like typ but if the argument is nil it is replaced with Typ[Invalid].
 // A nil type may appear in pathological cases such as type T[P any] []func(_ T([]_))
 // where an array/slice element is accessed before it is set up.