go/types: : generate assignments.go from types2 source

This CL reduces the amount of code that needs to be maintained
manually by about 600 LOC.

Change-Id: I7107c8050075281bf6840a9f5234d70e09734ce6
Reviewed-on: https://go-review.googlesource.com/c/go/+/565836
Auto-Submit: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>
Reviewed-by: Robert Griesemer <gri@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

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

@@ -24,7 +24,10 @@ func (check *Checker) assignment(x *operand, T Type, context string) {
 	switch x.mode {
 	case invalid:
 		return // error reported before
-	case constant_, variable, mapindex, value, nilvalue, commaok, commaerr:
+	case nilvalue:
+		assert(isTypes2)
+		// ok
+	case constant_, variable, mapindex, value, commaok, commaerr:
 		// ok
 	default:
 		// we may get here because of other problems (go.dev/issue/39634, crash 12)
@@ -41,6 +44,7 @@ func (check *Checker) assignment(x *operand, T Type, context string) {
 		// 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 isTypes2 {
 			if x.isNil() {
 				if T == nil {
 					check.errorf(x, UntypedNilUse, "use of untyped nil in %s", context)
@@ -50,6 +54,16 @@ func (check *Checker) assignment(x *operand, T Type, context string) {
 			} else if T == nil || isNonTypeParamInterface(T) {
 				target = Default(x.typ)
 			}
+		} else { // go/types
+			if T == nil || isNonTypeParamInterface(T) {
+				if T == nil && x.typ == Typ[UntypedNil] {
+					check.errorf(x, UntypedNilUse, "use of untyped nil in %s", context)
+					x.mode = invalid
+					return
+				}
+				target = Default(x.typ)
+			}
+		}
 		newType, val, code := check.implicitTypeAndValue(x, target)
 		if code != 0 {
 			msg := check.sprintf("cannot use %s as %s value in %s", x, target, context)
@@ -245,7 +259,7 @@ func (check *Checker) assignVar(lhs, rhs syntax.Expr, x *operand, context string
 
 	if x == nil {
 		var target *target
-		// avoid calling syntax.String if not needed
+		// avoid calling ExprString if not needed
 		if T != nil {
 			if _, ok := under(T).(*Signature); ok {
 				target = newTarget(T, ExprString(lhs))
@@ -493,7 +507,7 @@ func (check *Checker) assignVars(lhs, orig_rhs []syntax.Expr) {
 	// orig_rhs[0] was already evaluated
 }
 
-func (check *Checker) shortVarDecl(pos syntax.Pos, lhs, rhs []syntax.Expr) {
+func (check *Checker) shortVarDecl(pos poser, lhs, rhs []syntax.Expr) {
 	top := len(check.delayed)
 	scope := check.scope
 
@@ -506,6 +520,7 @@ func (check *Checker) shortVarDecl(pos syntax.Pos, lhs, rhs []syntax.Expr) {
 		ident, _ := lhs.(*syntax.Name)
 		if ident == nil {
 			check.useLHS(lhs)
+			// TODO(gri) This is redundant with a go/parser error. Consider omitting in go/types?
 			check.errorf(lhs, BadDecl, "non-name %s on left side of :=", lhs)
 			hasErr = true
 			continue
@@ -568,7 +583,7 @@ func (check *Checker) shortVarDecl(pos syntax.Pos, lhs, rhs []syntax.Expr) {
 	// a function begins at the end of the ConstSpec or VarSpec (ShortVarDecl
 	// for short variable declarations) and ends at the end of the innermost
 	// containing block."
-	scopePos := syntax.EndPos(rhs[len(rhs)-1])
+	scopePos := endPos(rhs[len(rhs)-1])
 	for _, obj := range newVars {
 		check.declare(scope, nil, obj, scopePos) // id = nil: recordDef already called
 	}

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

@@ -27,7 +27,7 @@ const (
 	variable                     // operand is an addressable variable
 	mapindex                     // operand is a map index expression (acts like a variable on lhs, commaok on rhs of an assignment)
 	value                        // operand is a computed value
-	nilvalue                     // operand is the nil value
+	nilvalue                     // operand is the nil value - only used by types2
 	commaok                      // like value, but operand may be used in a comma,ok expression
 	commaerr                     // like commaok, but second value is error, not boolean
 	cgofunc                      // operand is a cgo function
@@ -42,7 +42,7 @@ var operandModeString = [...]string{
 	variable:  "variable",
 	mapindex:  "map index expression",
 	value:     "value",
-	nilvalue:  "nil",
+	nilvalue:  "nil", // only used by types2
 	commaok:   "comma, ok expression",
 	commaerr:  "comma, error expression",
 	cgofunc:   "cgo function",

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

@@ -33,9 +33,10 @@ func dddErrPos(call *syntax.CallExpr) *syntax.CallExpr {
 }
 
 // argErrPos returns the node (poser) for reportign an invalid argument count.
-func argErrPos(call *syntax.CallExpr) *syntax.CallExpr {
+func argErrPos(call *syntax.CallExpr) *syntax.CallExpr { return call }
-	return call
-}
 
 // ExprString returns a string representation of x.
 func ExprString(x syntax.Node) string { return syntax.String(x) }
+
+// endPos returns the position of the first character immediately after node n.
+func endPos(n syntax.Node) syntax.Pos { return syntax.EndPos(n) }

src/go/types/assignments.go

@@ -1,3 +1,5 @@
+// Code generated by "go test -run=Generate -write=all"; DO NOT EDIT.
+
 // Copyright 2013 The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
@@ -24,6 +26,9 @@ func (check *Checker) assignment(x *operand, T Type, context string) {
 	switch x.mode {
 	case invalid:
 		return // error reported before
+	case nilvalue:
+		assert(isTypes2)
+		// ok
 	case constant_, variable, mapindex, value, commaok, commaerr:
 		// ok
 	default:
@@ -41,6 +46,17 @@ func (check *Checker) assignment(x *operand, T Type, context string) {
 		// 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 isTypes2 {
+			if x.isNil() {
+				if T == nil {
+					check.errorf(x, UntypedNilUse, "use of untyped nil in %s", context)
+					x.mode = invalid
+					return
+				}
+			} else if T == nil || isNonTypeParamInterface(T) {
+				target = Default(x.typ)
+			}
+		} else { // go/types
 			if T == nil || isNonTypeParamInterface(T) {
 				if T == nil && x.typ == Typ[UntypedNil] {
 					check.errorf(x, UntypedNilUse, "use of untyped nil in %s", context)
@@ -49,6 +65,7 @@ func (check *Checker) assignment(x *operand, T Type, context string) {
 				}
 				target = Default(x.typ)
 			}
+		}
 		newType, val, code := check.implicitTypeAndValue(x, target)
 		if code != 0 {
 			msg := check.sprintf("cannot use %s as %s value in %s", x, target, context)
@@ -505,7 +522,7 @@ func (check *Checker) shortVarDecl(pos positioner, lhs, rhs []ast.Expr) {
 		ident, _ := lhs.(*ast.Ident)
 		if ident == nil {
 			check.useLHS(lhs)
-			// TODO(rFindley) this is redundant with a parser error. Consider omitting?
+			// TODO(gri) This is redundant with a go/parser error. Consider omitting in go/types?
 			check.errorf(lhs, BadDecl, "non-name %s on left side of :=", lhs)
 			hasErr = true
 			continue
@@ -568,7 +585,7 @@ func (check *Checker) shortVarDecl(pos positioner, lhs, rhs []ast.Expr) {
 	// a function begins at the end of the ConstSpec or VarSpec (ShortVarDecl
 	// for short variable declarations) and ends at the end of the innermost
 	// containing block."
-	scopePos := rhs[len(rhs)-1].End()
+	scopePos := endPos(rhs[len(rhs)-1])
 	for _, obj := range newVars {
 		check.declare(scope, nil, obj, scopePos) // id = nil: recordDef already called
 	}

src/go/types/generate_test.go

@@ -96,6 +96,11 @@ type action func(in *ast.File)
 
 var filemap = map[string]action{
 	"alias.go": nil,
+	"assignments.go": func(f *ast.File) {
+		renameImportPath(f, `"cmd/compile/internal/syntax"->"go/ast"`)
+		renameSelectorExprs(f, "syntax.Name->ast.Ident", "ident.Value->ident.Name", "ast.Pos->token.Pos") // must happen before renaming identifiers
+		renameIdents(f, "syntax->ast", "poser->positioner", "nopos->noposn")
+	},
 	"array.go":          nil,
 	"api_predicates.go": nil,
 	"basic.go":          nil,

src/go/types/operand.go

@@ -26,6 +26,7 @@ const (
 	variable                     // operand is an addressable variable
 	mapindex                     // operand is a map index expression (acts like a variable on lhs, commaok on rhs of an assignment)
 	value                        // operand is a computed value
+	nilvalue                     // operand is the nil value - only used by types2
 	commaok                      // like value, but operand may be used in a comma,ok expression
 	commaerr                     // like commaok, but second value is error, not boolean
 	cgofunc                      // operand is a cgo function
@@ -40,6 +41,7 @@ var operandModeString = [...]string{
 	variable:  "variable",
 	mapindex:  "map index expression",
 	value:     "value",
+	nilvalue:  "nil", // only used by types2
 	commaok:   "comma, ok expression",
 	commaerr:  "comma, error expression",
 	cgofunc:   "cgo function",

src/go/types/util.go

@@ -30,11 +30,10 @@ func cmpPos(p, q token.Pos) int { return int(p - q) }
 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 {
+func dddErrPos(call *ast.CallExpr) positioner { return atPos(call.Ellipsis) }
-	return atPos(call.Ellipsis)
-}
 
 // argErrPos returns positioner for reportign an invalid argument count.
-func argErrPos(call *ast.CallExpr) positioner {
+func argErrPos(call *ast.CallExpr) positioner { return inNode(call, call.Rparen) }
-	return inNode(call, call.Rparen)
+
-}
+// endPos returns the position of the first character immediately after node n.
+func endPos(n ast.Node) token.Pos { return n.End() }