go/types: removed instantiate call, renamed instantiate2 => instantiate

Also: added a currently failing test case to testdata/tmp.go2

Change-Id: I605bffb457e3b3979b42a642010215630c0544c6

src/go/types/call.go

@@ -81,13 +81,32 @@ func (check *Checker) call(x *operand, e *ast.CallExpr) exprKind {
 		args, _ := check.exprOrTypeList(e.Args)
 
 		// instantiate function if needed
-		if n := len(args); len(sig.tparams) > 0 && n > 0 && args[0].mode == typexpr {
+		if n := len(args); n > 0 && len(sig.tparams) > 0 && args[0].mode == typexpr {
 			// if the first argument is a type, assume we have explicit type arguments
-			x.mode = value
-			x.typ = check.instantiate(sig, sig.tparams, args)
-			if x.typ == nil {
+
+			// we must have the correct number of type parameters
+			if n != len(sig.tparams) {
+				check.errorf(args[n-1].pos(), "got %d type arguments but want %d", n, len(sig.tparams))
 				x.mode = invalid
+				x.expr = e
+				return expression
 			}
+
+			// collect types
+			targs := make([]Type, n)
+			for i, a := range args {
+				if a.mode != typexpr {
+					// error was reported earlier
+					x.mode = invalid
+					x.expr = e
+					return expression
+				}
+				targs[i] = a.typ
+			}
+
+			// instantiate function signature
+			x.typ = check.subst(x.pos(), sig, sig.tparams, targs)
+			x.mode = value
 			x.expr = e
 			return expression
 		}
@@ -172,26 +191,6 @@ func (check *Checker) exprOrTypeList(elist []ast.Expr) (xlist []*operand, ok boo
 	return
 }
 
-func (check *Checker) instantiate(typ Type, tparams []*TypeName, args []*operand) Type {
-	assert(typ != nil)
-	n := len(args)
-	if n != len(tparams) {
-		check.errorf(args[n-1].pos(), "got %d type arguments but want %d", n, len(tparams))
-		return nil
-	}
-	// collect types
-	targs := make([]Type, n)
-	for i, a := range args {
-		if a.mode != typexpr {
-			// error was reported earlier
-			return nil
-		}
-		targs[i] = a.typ
-	}
-	// result is instantiated typ
-	return check.subst(token.NoPos, typ, tparams, targs)
-}
-
 func (check *Checker) exprList(elist []ast.Expr, allowCommaOk bool) (xlist []*operand, commaOk bool) {
 	switch len(elist) {
 	case 0:

src/go/types/subst.go

@@ -14,7 +14,7 @@ import (
 	"strings"
 )
 
-func (check *Checker) instantiate2(pos token.Pos, named *Named, targs []Type) (res Type) {
+func (check *Checker) instantiate(pos token.Pos, named *Named, targs []Type) (res Type) {
 	tname := named.obj
 	if check.conf.Trace {
 		check.trace(pos, "-- instantiating %s with %s", tname, typeListString(targs))

src/go/types/testdata/tmp.go2

@@ -4,6 +4,16 @@
 
 package p
 
+type T(type P) struct {}
+
+func (_ T(P)) m1() T(P)
+
+func (m T(P)) m2() {
+	// TODO(gri) this should be valid
+	var _ T(P) = m /* ERROR cannot use */ .m1()
+}
+
+/*
 type Pair(type K) struct {
 	key K
 }
@@ -16,7 +26,6 @@ type Iterator(type K) struct {
 	r Receiver(Pair(K))
 }
 
-/*
 func (r Receiver(T)) Values() T {
 	return r.values
 }

src/go/types/typexpr.go

@@ -302,7 +302,7 @@ func (check *Checker) typInternal(e ast.Expr, def *Named) Type {
 		}
 
 		// instantiate parameterized type
-		typ = check.instantiate2(e.Pos(), named, targs)
+		typ = check.instantiate(e.Pos(), named, targs)
 		def.setUnderlying(typ)
 		return typ