go/types: expose IsInterface predicate, eliminating 6 copies

Change-Id: I3704d7bd7a11f691c66556c1b77ef79a503d2fe9
Reviewed-on: https://go-review.googlesource.com/2173
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

11 files changed, 12 insertions, 35 deletions

diff --git a/go/pointer/util.go b/go/pointer/util.go
index 88bada8..d4ccbb5 100644
--- a/go/pointer/util.go
+++ b/go/pointer/util.go
@@ -50,11 +50,7 @@ func CanHaveDynamicTypes(T types.Type) bool {
 	return false
 }
 
-// isInterface reports whether T is an interface type.
-func isInterface(T types.Type) bool {
-	_, ok := T.Underlying().(*types.Interface)
-	return ok
-}
+func isInterface(T types.Type) bool { return types.IsInterface(T) }
 
 // mustDeref returns the element type of its argument, which must be a
 // pointer; panic ensues otherwise.
diff --git a/go/ssa/builder.go b/go/ssa/builder.go
index 1f9511e..93755d0 100644
--- a/go/ssa/builder.go
+++ b/go/ssa/builder.go
@@ -600,7 +600,7 @@ func (b *builder) expr0(fn *Function, e ast.Expr, tv types.TypeAndValue) Value {
 		case *types.Basic, *types.Slice, *types.Pointer: // *array
 			x = b.expr(fn, e.X)
 		default:
-			unreachable()
+			panic("unreachable")
 		}
 		if e.High != nil {
 			high = b.expr(fn, e.High)
diff --git a/go/ssa/util.go b/go/ssa/util.go
index cd476d8..10ebb8c 100644
--- a/go/ssa/util.go
+++ b/go/ssa/util.go
@@ -17,10 +17,6 @@ import (
 	"golang.org/x/tools/go/types"
 )
 
-func unreachable() {
-	panic("unreachable")
-}
-
 //// AST utilities
 
 func unparen(e ast.Expr) ast.Expr { return astutil.Unparen(e) }
@@ -41,11 +37,7 @@ func isPointer(typ types.Type) bool {
 	return ok
 }
 
-// isInterface reports whether T's underlying type is an interface.
-func isInterface(T types.Type) bool {
-	_, ok := T.Underlying().(*types.Interface)
-	return ok
-}
+func isInterface(T types.Type) bool { return types.IsInterface(T) }
 
 // deref returns a pointer's element type; otherwise it returns typ.
 func deref(typ types.Type) types.Type {
diff --git a/go/types/assignments.go b/go/types/assignments.go
index 7ee1abc..14ee286 100644
--- a/go/types/assignments.go
+++ b/go/types/assignments.go
@@ -45,7 +45,7 @@ func (check *Checker) assignment(x *operand, T Type) bool {
 		// bool, rune, int, float64, complex128 or string respectively, depending
 		// on whether the value is a boolean, rune, integer, floating-point, complex,
 		// or string constant."
-		if T == nil || isInterface(T) {
+		if T == nil || IsInterface(T) {
 			if T == nil && x.typ == Typ[UntypedNil] {
 				check.errorf(x.pos(), "use of untyped nil")
 				x.mode = invalid
diff --git a/go/types/call.go b/go/types/call.go
index 5811a12..7f366a8 100644
--- a/go/types/call.go
+++ b/go/types/call.go
@@ -397,7 +397,7 @@ func (check *Checker) selector(x *operand, e *ast.SelectorExpr) {
 					// includes the methods of typ.
 					// Variables are addressable, so we can always take their
 					// address.
-					if _, ok := typ.(*Pointer); !ok && !isInterface(typ) {
+					if _, ok := typ.(*Pointer); !ok && !IsInterface(typ) {
 						typ = &Pointer{base: typ}
 					}
 				}
diff --git a/go/types/conversions.go b/go/types/conversions.go
index 32cc822..f7b2a56 100644
--- a/go/types/conversions.go
+++ b/go/types/conversions.go
@@ -54,7 +54,7 @@ func (check *Checker) conversion(x *operand, T Type) {
 		//   use the default type (e.g., []byte("foo") should report string
 		//   not []byte as type for the constant "foo").
 		// - Keep untyped nil for untyped nil arguments.
-		if isInterface(T) || constArg && !isConstType(T) {
+		if IsInterface(T) || constArg && !isConstType(T) {
 			final = defaultType(x.typ)
 		}
 		check.updateExprType(x.expr, final, true)
diff --git a/go/types/predicates.go b/go/types/predicates.go
index 2e36a72..b5c39d9 100644
--- a/go/types/predicates.go
+++ b/go/types/predicates.go
@@ -71,7 +71,8 @@ func isConstType(typ Type) bool {
 	return ok && t.info&IsConstType != 0
 }
 
-func isInterface(typ Type) bool {
+// IsInterface reports whether typ is an interface type.
+func IsInterface(typ Type) bool {
 	_, ok := typ.Underlying().(*Interface)
 	return ok
 }
diff --git a/godoc/analysis/typeinfo.go b/godoc/analysis/typeinfo.go
index 82f2f29..bd1b0c1 100644
--- a/godoc/analysis/typeinfo.go
+++ b/godoc/analysis/typeinfo.go
@@ -215,10 +215,7 @@ func (a *analysis) namedType(obj *types.TypeName, implements map[*types.Named]im
 
 // -- utilities --------------------------------------------------------
 
-func isInterface(T types.Type) bool {
-	_, isI := T.Underlying().(*types.Interface)
-	return isI
-}
+func isInterface(T types.Type) bool { return types.IsInterface(T) }
 
 // deref returns a pointer's element type; otherwise it returns typ.
 func deref(typ types.Type) types.Type {
diff --git a/oracle/implements.go b/oracle/implements.go
index d07a02c..8e54dea 100644
--- a/oracle/implements.go
+++ b/oracle/implements.go
@@ -191,10 +191,7 @@ func typeKind(T types.Type) string {
 	return strings.ToLower(strings.TrimPrefix(s, "*types."))
 }
 
-func isInterface(T types.Type) bool {
-	_, isI := T.Underlying().(*types.Interface)
-	return isI
-}
+func isInterface(T types.Type) bool { return types.IsInterface(T) }
 
 type typesByString []types.Type
 
diff --git a/refactor/rename/check.go b/refactor/rename/check.go
index 324d099..017a604 100644
--- a/refactor/rename/check.go
+++ b/refactor/rename/check.go
@@ -727,10 +727,7 @@ func someUse(info *loader.PackageInfo, obj types.Object) *ast.Ident {
 
 // -- Plundered from golang.org/x/tools/go/ssa -----------------
 
-func isInterface(T types.Type) bool {
-	_, ok := T.Underlying().(*types.Interface)
-	return ok
-}
+func isInterface(T types.Type) bool { return types.IsInterface(T) }
 
 func deref(typ types.Type) types.Type {
 	if p, _ := typ.(*types.Pointer); p != nil {
diff --git a/refactor/satisfy/find.go b/refactor/satisfy/find.go
index 9770a02..20fb288 100644
--- a/refactor/satisfy/find.go
+++ b/refactor/satisfy/find.go
@@ -701,7 +701,4 @@ func deref(typ types.Type) types.Type {
 
 func unparen(e ast.Expr) ast.Expr { return astutil.Unparen(e) }
 
-func isInterface(T types.Type) bool {
-	_, ok := T.Underlying().(*types.Interface)
-	return ok
-}
+func isInterface(T types.Type) bool { return types.IsInterface(T) }