go/types, types2: remove superfluous argument test in Checker.arguments

There's only two places which call Checker.arguments: Checker.callExpr
and Checker.builtin. Both ensure that the passed argument list doesn't
contain type expressions, so we don't need that extra check at the start
of Checker.arguments.

The remaining check causes Checker.arguments to exit early if any of
the passed arguments is invalid. This reduces the number of reported
errors in rare cases but is executed all the time.
If the extra errors are a problem, it would be better to not call
Checker.arguments in the first place, or only do the extra check
before Checker.arguments reports an error.

Removing this code for now. Removes a long-standing TODO.

Change-Id: Ief654b680eb6b6a768bb1b4c621d3c8169953f17
Reviewed-on: https://go-review.googlesource.com/c/go/+/495395
Run-TryBot: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Robert Findley <rfindley@google.com>

Author: griesemer

src/cmd/compile/internal/types2/call.go

@@ -419,17 +419,6 @@ func (check *Checker) genericExprList(elist []syntax.Expr) []*operand {
 func (check *Checker) arguments(call *syntax.CallExpr, sig *Signature, targs []Type, xlist []syntax.Expr, args []*operand) (rsig *Signature) {
 	rsig = sig
 
-	// TODO(gri) try to eliminate this extra verification loop
-	for _, a := range args {
-		switch a.mode {
-		case typexpr:
-			check.errorf(a, NotAnExpr, "%s used as value", a)
-			return
-		case invalid:
-			return
-		}
-	}
-
 	// Function call argument/parameter count requirements
 	//
 	//               | standard call    | dotdotdot call |

src/go/types/call.go

@@ -424,17 +424,6 @@ func (check *Checker) genericExprList(elist []ast.Expr) []*operand {
 func (check *Checker) arguments(call *ast.CallExpr, sig *Signature, targs []Type, xlist []ast.Expr, args []*operand) (rsig *Signature) {
 	rsig = sig
 
-	// TODO(gri) try to eliminate this extra verification loop
-	for _, a := range args {
-		switch a.mode {
-		case typexpr:
-			check.errorf(a, NotAnExpr, "%s used as value", a)
-			return
-		case invalid:
-			return
-		}
-	}
-
 	// Function call argument/parameter count requirements
 	//
 	//               | standard call    | dotdotdot call |

src/internal/types/testdata/check/expr3.go

@@ -505,7 +505,7 @@ func _calls() {
 	f2(3.14) /* ERROR "not enough arguments in call to f2\n\thave (number)\n\twant (float32, string)" */
 	f2(3.14, "foo")
 	f2(x /* ERRORx `cannot use .* in argument` */ , "foo")
-	f2(g0 /* ERROR "used as value" */ ())
+	f2(g0 /* ERROR "used as value" */ ()) /* ERROR "not enough arguments in call to f2\n\thave (func())\n\twant (float32, string)" */
 	f2(g1()) /* ERROR "not enough arguments in call to f2\n\thave (int)\n\twant (float32, string)" */
 	f2(g2())
 

src/internal/types/testdata/fixedbugs/issue39634.go

@@ -66,7 +66,7 @@ type Z19 [][[]Z19{}[0][0]]c19 /* ERROR "undefined" */
 
 // crash 20
 type Z20 /* ERROR "invalid recursive type" */ interface{ Z20 }
-func F20[t Z20]() { F20(t /* ERROR "invalid composite literal type" */ {}) }
+func F20[t Z20]() { F20(t /* ERROR "invalid composite literal type" */ /* ERROR "too many arguments in call to F20\n\thave (unknown type)\n\twant ()" */ {}) }
 
 // crash 21
 type Z21 /* ERROR "invalid recursive type" */ interface{ Z21 }