go/types, types2: factor out isdddArray and inNode helper functions

Preparation for generation of go/types/literals.go from types2 sources.

Change-Id: I9af23fbe1e448976394ddd7b348188c2595d8afe
Reviewed-on: https://go-review.googlesource.com/c/go/+/610557
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Tim King <taking@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>

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

@@ -20,7 +20,7 @@ func (check *Checker) compositeLit(T *target, x *operand, e *syntax.CompositeLit
 		// composite literal type present - use it
 		// [...]T array types may only appear with composite literals.
 		// Check for them here so we don't have to handle ... in general.
-		if atyp, _ := e.Type.(*syntax.ArrayType); atyp != nil && atyp.Len == nil {
+		if atyp, _ := e.Type.(*syntax.ArrayType); atyp != nil && isdddArray(atyp) {
 			// We have an "open" [...]T array type.
 			// Create a new ArrayType with unknown length (-1)
 			// and finish setting it up after analyzing the literal.
@@ -124,7 +124,7 @@ func (check *Checker) compositeLit(T *target, x *operand, e *syntax.CompositeLit
 				check.assignment(x, etyp, "struct literal")
 			}
 			if len(e.ElemList) < len(fields) {
-				check.errorf(e.Rbrace, InvalidStructLit, "too few values in struct literal of type %s", base)
+				check.errorf(inNode(e, e.Rbrace), InvalidStructLit, "too few values in struct literal of type %s", base)
 				// ok to continue
 			}
 		}

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

@@ -36,6 +36,9 @@ func dddErrPos(call *syntax.CallExpr) *syntax.CallExpr {
 	return call
 }
 
+// isdddArray reports whether atyp is of the form [...]E.
+func isdddArray(atyp *syntax.ArrayType) bool { return atyp.Len == nil }
+
 // argErrPos returns the node (poser) for reporting an invalid argument count.
 func argErrPos(call *syntax.CallExpr) *syntax.CallExpr { return call }
 
@@ -48,6 +51,9 @@ func startPos(n syntax.Node) syntax.Pos { return syntax.StartPos(n) }
 // endPos returns the position of the first character immediately after node n.
 func endPos(n syntax.Node) syntax.Pos { return syntax.EndPos(n) }
 
+// inNode is a dummy function returning pos.
+func inNode(_ syntax.Node, pos syntax.Pos) syntax.Pos { return pos }
+
 // makeFromLiteral returns the constant value for the given literal string and kind.
 func makeFromLiteral(lit string, kind syntax.LitKind) constant.Value {
 	return constant.MakeFromLiteral(lit, kind2tok[kind], 0)

src/go/types/literals.go

@@ -20,15 +20,13 @@ func (check *Checker) compositeLit(T *target, x *operand, e *ast.CompositeLit, h
 		// composite literal type present - use it
 		// [...]T array types may only appear with composite literals.
 		// Check for them here so we don't have to handle ... in general.
-		if atyp, _ := e.Type.(*ast.ArrayType); atyp != nil && atyp.Len != nil {
-			if ellip, _ := atyp.Len.(*ast.Ellipsis); ellip != nil && ellip.Elt == nil {
-				// We have an "open" [...]T array type.
-				// Create a new ArrayType with unknown length (-1)
-				// and finish setting it up after analyzing the literal.
-				typ = &Array{len: -1, elem: check.varType(atyp.Elt)}
-				base = typ
-				break
-			}
+		if atyp, _ := e.Type.(*ast.ArrayType); atyp != nil && isdddArray(atyp) {
+			// We have an "open" [...]T array type.
+			// Create a new ArrayType with unknown length (-1)
+			// and finish setting it up after analyzing the literal.
+			typ = &Array{len: -1, elem: check.varType(atyp.Elt)}
+			base = typ
+			break
 		}
 		typ = check.typ(e.Type)
 		base = typ

src/go/types/util.go

@@ -33,6 +33,16 @@ func hasDots(call *ast.CallExpr) bool { return call.Ellipsis.IsValid() }
 // dddErrPos returns the positioner for reporting an invalid ... use in a call.
 func dddErrPos(call *ast.CallExpr) positioner { return atPos(call.Ellipsis) }
 
+// isdddArray reports whether atyp is of the form [...]E.
+func isdddArray(atyp *ast.ArrayType) bool {
+	if atyp.Len != nil {
+		if ddd, _ := atyp.Len.(*ast.Ellipsis); ddd != nil && ddd.Elt == nil {
+			return true
+		}
+	}
+	return false
+}
+
 // argErrPos returns positioner for reporting an invalid argument count.
 func argErrPos(call *ast.CallExpr) positioner { return inNode(call, call.Rparen) }