go/types, types2: factor out position comparison, share more code

This CL introduces the new files util.go and util_test.go for both
type checkers; these files factor out functionality that is different
between the type checkers so that more code (that is otherwise mostly
the same) can be generated.

With cmpPos/CmpPos factored out, go/types/scope.go can now be generated.

Change-Id: I35f67e53d83b3c5086a559b1e826db83d38ee217
Reviewed-on: https://go-review.googlesource.com/c/go/+/461596
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@google.com>
Run-TryBot: Robert Griesemer <gri@google.com>
Auto-Submit: Robert Griesemer <gri@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>

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

@@ -622,7 +622,7 @@ func sortedInstances(m map[*syntax.Name]Instance) (instances []recordedInstance)
 		instances = append(instances, recordedInstance{id, inst})
 	}
 	sort.Slice(instances, func(i, j int) bool {
-		return instances[i].Name.Pos().Cmp(instances[j].Name.Pos()) < 0
+		return CmpPos(instances[i].Name.Pos(), instances[j].Name.Pos()) < 0
 	})
 	return instances
 }

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

@@ -360,7 +360,7 @@ func (check *Checker) cycleError(cycle []Object) {
 func firstInSrc(path []Object) int {
 	fst, pos := 0, path[0].Pos()
 	for i, t := range path[1:] {
-		if t.Pos().Cmp(pos) < 0 {
+		if cmpPos(t.Pos(), pos) < 0 {
 			fst, pos = i+1, t.Pos()
 		}
 	}

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

@@ -284,7 +284,7 @@ func (w *monoGraph) localNamedVertex(pkg *Package, named *Named) int {
 	// parameters that it's implicitly parameterized by.
 	for scope := obj.Parent(); scope != root; scope = scope.Parent() {
 		for _, elem := range scope.elems {
-			if elem, ok := elem.(*TypeName); ok && !elem.IsAlias() && elem.Pos().Cmp(obj.Pos()) < 0 {
+			if elem, ok := elem.(*TypeName); ok && !elem.IsAlias() && cmpPos(elem.Pos(), obj.Pos()) < 0 {
 				if tpar, ok := elem.Type().(*TypeParam); ok {
 					if idx < 0 {
 						idx = len(w.vertices)

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

@@ -83,7 +83,7 @@ func (s *Scope) Lookup(name string) Object {
 // whose scope is the scope of the package that exported them.
 func (s *Scope) LookupParent(name string, pos syntax.Pos) (*Scope, Object) {
 	for ; s != nil; s = s.parent {
-		if obj := s.Lookup(name); obj != nil && (!pos.IsKnown() || obj.scopePos().Cmp(pos) <= 0) {
+		if obj := s.Lookup(name); obj != nil && (!pos.IsKnown() || cmpPos(obj.scopePos(), pos) <= 0) {
 			return s, obj
 		}
 	}
@@ -175,7 +175,7 @@ func (s *Scope) End() syntax.Pos { return s.end }
 // The result is guaranteed to be valid only if the type-checked
 // AST has complete position information.
 func (s *Scope) Contains(pos syntax.Pos) bool {
-	return s.pos.Cmp(pos) <= 0 && pos.Cmp(s.end) < 0
+	return cmpPos(s.pos, pos) <= 0 && cmpPos(pos, s.end) < 0
 }
 
 // Innermost returns the innermost (child) scope containing

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

@@ -64,7 +64,7 @@ func (check *Checker) usage(scope *Scope) {
 		}
 	}
 	sort.Slice(unused, func(i, j int) bool {
-		return unused[i].pos.Cmp(unused[j].pos) < 0
+		return cmpPos(unused[i].pos, unused[j].pos) < 0
 	})
 	for _, v := range unused {
 		check.softErrorf(v.pos, UnusedVar, "%s declared and not used", v.name)

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

@@ -0,0 +1,22 @@
+// Copyright 2023 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.
+
+// This file contains various functionality that is
+// different between go/types and types2. Factoring
+// out this code allows more of the rest of the code
+// to be shared.
+
+package types2
+
+import "cmd/compile/internal/syntax"
+
+// cmpPos compares the positions p and q and returns a result r as follows:
+//
+// r <  0: p is before q
+// r == 0: p and q are the same position (but may not be identical)
+// r >  0: p is after q
+//
+// If p and q are in different files, p is before q if the filename
+// of p sorts lexicographically before the filename of q.
+func cmpPos(p, q syntax.Pos) int { return p.Cmp(q) }

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

@@ -0,0 +1,12 @@
+// Copyright 2023 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.
+
+// This file exports various functionality of util.go
+// so that it can be used in (package-external) tests.
+
+package types2
+
+import "cmd/compile/internal/syntax"
+
+func CmpPos(p, q syntax.Pos) int { return cmpPos(p, q) }

src/go/types/api_test.go

@@ -620,7 +620,7 @@ func sortedInstances(m map[*ast.Ident]Instance) (instances []recordedInstance) {
 		instances = append(instances, recordedInstance{id, inst})
 	}
 	sort.Slice(instances, func(i, j int) bool {
-		return instances[i].Ident.Pos() < instances[j].Ident.Pos()
+		return CmpPos(instances[i].Ident.Pos(), instances[j].Ident.Pos()) < 0
 	})
 	return instances
 }

src/go/types/decl.go

@@ -355,7 +355,7 @@ func (check *Checker) cycleError(cycle []Object) {
 func firstInSrc(path []Object) int {
 	fst, pos := 0, path[0].Pos()
 	for i, t := range path[1:] {
-		if t.Pos() < pos {
+		if cmpPos(t.Pos(), pos) < 0 {
 			fst, pos = i+1, t.Pos()
 		}
 	}

src/go/types/generator.go

@@ -80,20 +80,25 @@ var filemap = map[string]action{
 	"package.go":          nil,
 	"pointer.go":          nil,
 	"predicates.go":       nil,
-	"selection.go":        nil,
-	"sizes.go":            func(f *ast.File) { renameIdent(f, "IsSyncAtomicAlign64", "isSyncAtomicAlign64") },
-	"slice.go":            nil,
-	"subst.go":            func(f *ast.File) { fixTokenPos(f); fixTraceSel(f) },
-	"termlist.go":         nil,
-	"termlist_test.go":    nil,
-	"tuple.go":            nil,
-	"typelists.go":        nil,
-	"typeparam.go":        nil,
-	"typeterm_test.go":    nil,
-	"typeterm.go":         nil,
-	"under.go":            nil,
-	"universe.go":         fixGlobalTypVarDecl,
-	"validtype.go":        nil,
+	"scope.go": func(f *ast.File) {
+		fixTokenPos(f)
+		renameIdent(f, "Squash", "squash")
+		renameIdent(f, "InsertLazy", "_InsertLazy")
+	},
+	"selection.go":     nil,
+	"sizes.go":         func(f *ast.File) { renameIdent(f, "IsSyncAtomicAlign64", "isSyncAtomicAlign64") },
+	"slice.go":         nil,
+	"subst.go":         func(f *ast.File) { fixTokenPos(f); fixTraceSel(f) },
+	"termlist.go":      nil,
+	"termlist_test.go": nil,
+	"tuple.go":         nil,
+	"typelists.go":     nil,
+	"typeparam.go":     nil,
+	"typeterm_test.go": nil,
+	"typeterm.go":      nil,
+	"under.go":         nil,
+	"universe.go":      fixGlobalTypVarDecl,
+	"validtype.go":     nil,
 }
 
 // TODO(gri) We should be able to make these rewriters more configurable/composable.
@@ -134,15 +139,23 @@ func fixTokenPos(f *ast.File) {
 	ast.Inspect(f, func(n ast.Node) bool {
 		switch n := n.(type) {
 		case *ast.ImportSpec:
+			// rewrite import path "cmd/compile/internal/syntax" to "go/token"
 			if n.Path.Kind == token.STRING && n.Path.Value == `"cmd/compile/internal/syntax"` {
 				n.Path.Value = `"go/token"`
 				return false
 			}
 		case *ast.SelectorExpr:
+			// rewrite syntax.Pos to token.Pos
 			if x, _ := n.X.(*ast.Ident); x != nil && x.Name == "syntax" && n.Sel.Name == "Pos" {
 				x.Name = "token"
 				return false
 			}
+		case *ast.CallExpr:
+			// rewrite x.IsKnown() to x.IsValid()
+			if fun, _ := n.Fun.(*ast.SelectorExpr); fun != nil && fun.Sel.Name == "IsKnown" && len(n.Args) == 0 {
+				fun.Sel.Name = "IsValid"
+				return false
+			}
 		}
 		return true
 	})
@@ -153,6 +166,7 @@ func fixTraceSel(f *ast.File) {
 	ast.Inspect(f, func(n ast.Node) bool {
 		switch n := n.(type) {
 		case *ast.SelectorExpr:
+			// rewrite x.Trace to x.trace (for Config.Trace)
 			if n.Sel.Name == "Trace" {
 				n.Sel.Name = "trace"
 				return false
@@ -169,6 +183,7 @@ func fixGlobalTypVarDecl(f *ast.File) {
 	ast.Inspect(f, func(n ast.Node) bool {
 		switch n := n.(type) {
 		case *ast.ValueSpec:
+			// rewrite type Typ = [...]Type{...} to type Typ = []Type{...}
 			if len(n.Names) == 1 && n.Names[0].Name == "Typ" && len(n.Values) == 1 {
 				n.Values[0].(*ast.CompositeLit).Type.(*ast.ArrayType).Len = nil
 				return false

src/go/types/mono.go

@@ -282,7 +282,7 @@ func (w *monoGraph) localNamedVertex(pkg *Package, named *Named) int {
 	// parameters that it's implicitly parameterized by.
 	for scope := obj.Parent(); scope != root; scope = scope.Parent() {
 		for _, elem := range scope.elems {
-			if elem, ok := elem.(*TypeName); ok && !elem.IsAlias() && elem.Pos() < obj.Pos() {
+			if elem, ok := elem.(*TypeName); ok && !elem.IsAlias() && cmpPos(elem.Pos(), obj.Pos()) < 0 {
 				if tpar, ok := elem.Type().(*TypeParam); ok {
 					if idx < 0 {
 						idx = len(w.vertices)

src/go/types/scope.go

@@ -1,3 +1,5 @@
+// Code generated by "go run generator.go"; 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.
@@ -83,7 +85,7 @@ func (s *Scope) Lookup(name string) Object {
 // whose scope is the scope of the package that exported them.
 func (s *Scope) LookupParent(name string, pos token.Pos) (*Scope, Object) {
 	for ; s != nil; s = s.parent {
-		if obj := s.Lookup(name); obj != nil && (!pos.IsValid() || obj.scopePos() <= pos) {
+		if obj := s.Lookup(name); obj != nil && (!pos.IsValid() || cmpPos(obj.scopePos(), pos) <= 0) {
 			return s, obj
 		}
 	}
@@ -107,11 +109,11 @@ func (s *Scope) Insert(obj Object) Object {
 	return nil
 }
 
-// _InsertLazy is like Insert, but allows deferring construction of the
+// InsertLazy is like Insert, but allows deferring construction of the
 // inserted object until it's accessed with Lookup. The Object
-// returned by resolve must have the same name as given to _InsertLazy.
+// returned by resolve must have the same name as given to InsertLazy.
 // If s already contains an alternative object with the same name,
-// _InsertLazy leaves s unchanged and returns false. Otherwise it
+// InsertLazy leaves s unchanged and returns false. Otherwise it
 // records the binding and returns true. The object's parent scope
 // will be set to s after resolve is called.
 func (s *Scope) _InsertLazy(name string, resolve func() Object) bool {
@@ -129,7 +131,7 @@ func (s *Scope) insert(name string, obj Object) {
 	s.elems[name] = obj
 }
 
-// squash merges s with its parent scope p by adding all
+// Squash merges s with its parent scope p by adding all
 // objects of s to p, adding all children of s to the
 // children of p, and removing s from p's children.
 // The function f is called for each object obj in s which
@@ -175,7 +177,7 @@ func (s *Scope) End() token.Pos { return s.end }
 // The result is guaranteed to be valid only if the type-checked
 // AST has complete position information.
 func (s *Scope) Contains(pos token.Pos) bool {
-	return s.pos <= pos && pos < s.end
+	return cmpPos(s.pos, pos) <= 0 && cmpPos(pos, s.end) < 0
 }
 
 // Innermost returns the innermost (child) scope containing

src/go/types/stmt.go

@@ -65,7 +65,7 @@ func (check *Checker) usage(scope *Scope) {
 		}
 	}
 	sort.Slice(unused, func(i, j int) bool {
-		return unused[i].pos < unused[j].pos
+		return cmpPos(unused[i].pos, unused[j].pos) < 0
 	})
 	for _, v := range unused {
 		check.softErrorf(v, UnusedVar, "%s declared and not used", v.name)

src/go/types/util.go

@@ -0,0 +1,22 @@
+// Copyright 2023 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.
+
+// This file contains various functionality that is
+// different between go/types and types2. Factoring
+// out this code allows more of the rest of the code
+// to be shared.
+
+package types
+
+import "go/token"
+
+// cmpPos compares the positions p and q and returns a result r as follows:
+//
+// r <  0: p is before q
+// r == 0: p and q are the same position (but may not be identical)
+// r >  0: p is after q
+//
+// If p and q are in different files, p is before q if the filename
+// of p sorts lexicographically before the filename of q.
+func cmpPos(p, q token.Pos) int { return int(p - q) }

src/go/types/util_test.go

@@ -0,0 +1,12 @@
+// Copyright 2023 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.
+
+// This file exports various functionality of util.go
+// so that it can be used in (package-external) tests.
+
+package types
+
+import "go/token"
+
+func CmpPos(p, q token.Pos) int { return cmpPos(p, q) }