cmd/compile: remove -G flag

Post 1.18, we're committed to types2 as cmd/compile's type checker.

Change-Id: I30d2dd2b2ba62832fcdcaeb996fcbc8a4a05d591
Reviewed-on: https://go-review.googlesource.com/c/go/+/388535
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Trust: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Keith Randall <khr@golang.org>

src/cmd/compile/internal/base/flag.go

@@ -55,7 +55,6 @@ type CmdFlags struct {
 	C CountFlag    "help:\"disable printing of columns in error messages\""
 	D string       "help:\"set relative `path` for local imports\""
 	E CountFlag    "help:\"debug symbol export\""
-	G CountFlag    "help:\"accept generic code\""
 	I func(string) "help:\"add `directory` to import search path\""
 	K CountFlag    "help:\"debug missing line numbers\""
 	L CountFlag    "help:\"show full file names in error messages\""
@@ -141,7 +140,6 @@ type CmdFlags struct {
 
 // ParseFlags parses the command-line flags into Flag.
 func ParseFlags() {
-	Flag.G = 3
 	Flag.I = addImportDir
 
 	Flag.LowerC = 1

src/cmd/compile/internal/noder/irgen.go

@@ -6,7 +6,6 @@ package noder
 
 import (
 	"fmt"
-	"os"
 
 	"cmd/compile/internal/base"
 	"cmd/compile/internal/dwarfgen"
@@ -77,10 +76,6 @@ func checkFiles(noders []*noder) (posMap, *types2.Package, *types2.Info) {
 func check2(noders []*noder) {
 	m, pkg, info := checkFiles(noders)
 
-	if base.Flag.G < 2 {
-		os.Exit(0)
-	}
-
 	g := irgen{
 		target: typecheck.Target,
 		self:   pkg,
@@ -90,10 +85,6 @@ func check2(noders []*noder) {
 		typs:   make(map[types2.Type]*types.Type),
 	}
 	g.generate(noders)
-
-	if base.Flag.G < 3 {
-		os.Exit(0)
-	}
 }
 
 // Information about sub-dictionary entries in a dictionary

src/cmd/compile/internal/noder/noder.go

@@ -9,7 +9,6 @@ import (
 	"fmt"
 	"go/constant"
 	"go/token"
-	"internal/buildcfg"
 	"os"
 	"path/filepath"
 	"runtime"
@@ -31,13 +30,7 @@ import (
 func LoadPackage(filenames []string) {
 	base.Timer.Start("fe", "parse")
 
-	// -G=3 and unified expect generics syntax, but -G=0 does not.
+	mode := syntax.CheckBranches | syntax.AllowGenerics
-	supportsGenerics := base.Flag.G != 0 || buildcfg.Experiment.Unified
-
-	mode := syntax.CheckBranches
-	if supportsGenerics {
-		mode |= syntax.AllowGenerics
-	}
 
 	// Limit the number of simultaneously open files.
 	sem := make(chan struct{}, runtime.GOMAXPROCS(0)+10)
@@ -85,104 +78,8 @@ func LoadPackage(filenames []string) {
 		return
 	}
 
-	if base.Flag.G != 0 {
+	// Use types2 to type-check and generate IR.
-		// Use types2 to type-check and possibly generate IR.
+	check2(noders)
-		check2(noders)
-		return
-	}
-
-	for _, p := range noders {
-		p.node()
-		p.file = nil // release memory
-	}
-
-	if base.SyntaxErrors() != 0 {
-		base.ErrorExit()
-	}
-	types.CheckDclstack()
-
-	for _, p := range noders {
-		p.processPragmas()
-	}
-
-	// Typecheck.
-	types.LocalPkg.Height = myheight
-	typecheck.DeclareUniverse()
-	typecheck.TypecheckAllowed = true
-
-	// Process top-level declarations in phases.
-
-	// Phase 1: const, type, and names and types of funcs.
-	//   This will gather all the information about types
-	//   and methods but doesn't depend on any of it.
-	//
-	//   We also defer type alias declarations until phase 2
-	//   to avoid cycles like #18640.
-	//   TODO(gri) Remove this again once we have a fix for #25838.
-	//
-	// Phase 2: Variable assignments.
-	//   To check interface assignments, depends on phase 1.
-
-	// Don't use range--typecheck can add closures to Target.Decls.
-	for phase, name := range []string{"top1", "top2"} {
-		base.Timer.Start("fe", "typecheck", name)
-		for i := 0; i < len(typecheck.Target.Decls); i++ {
-			n := typecheck.Target.Decls[i]
-			op := n.Op()
-
-			// Closure function declarations are typechecked as part of the
-			// closure expression.
-			if fn, ok := n.(*ir.Func); ok && fn.OClosure != nil {
-				continue
-			}
-
-			// We don't actually add ir.ODCL nodes to Target.Decls. Make sure of that.
-			if op == ir.ODCL {
-				base.FatalfAt(n.Pos(), "unexpected top declaration: %v", op)
-			}
-
-			// Identify declarations that should be deferred to the second
-			// iteration.
-			late := op == ir.OAS || op == ir.OAS2 || op == ir.ODCLTYPE && n.(*ir.Decl).X.Alias()
-
-			if late == (phase == 1) {
-				typecheck.Target.Decls[i] = typecheck.Stmt(n)
-			}
-		}
-	}
-
-	// Phase 3: Type check function bodies.
-	// Don't use range--typecheck can add closures to Target.Decls.
-	base.Timer.Start("fe", "typecheck", "func")
-	for i := 0; i < len(typecheck.Target.Decls); i++ {
-		if fn, ok := typecheck.Target.Decls[i].(*ir.Func); ok {
-			if base.Flag.W > 1 {
-				s := fmt.Sprintf("\nbefore typecheck %v", fn)
-				ir.Dump(s, fn)
-			}
-			typecheck.FuncBody(fn)
-			if base.Flag.W > 1 {
-				s := fmt.Sprintf("\nafter typecheck %v", fn)
-				ir.Dump(s, fn)
-			}
-		}
-	}
-
-	// Phase 4: Check external declarations.
-	// TODO(mdempsky): This should be handled when type checking their
-	// corresponding ODCL nodes.
-	base.Timer.Start("fe", "typecheck", "externdcls")
-	for i, n := range typecheck.Target.Externs {
-		if n.Op() == ir.ONAME {
-			typecheck.Target.Externs[i] = typecheck.Expr(typecheck.Target.Externs[i])
-		}
-	}
-
-	// Phase 5: With all user code type-checked, it's now safe to verify map keys.
-	// With all user code typechecked, it's now safe to verify unused dot imports.
-	typecheck.CheckMapKeys()
-	CheckDotImports()
-	base.ExitIfErrors()
 }
 
 func (p *noder) errorAt(pos syntax.Pos, format string, args ...interface{}) {

src/cmd/compile/internal/reflectdata/reflect.go

@@ -1397,9 +1397,7 @@ func WriteBasicTypes() {
 		}
 		writeType(types.NewPtr(types.Types[types.TSTRING]))
 		writeType(types.NewPtr(types.Types[types.TUNSAFEPTR]))
-		if base.Flag.G > 0 {
+		writeType(types.AnyType)
-			writeType(types.AnyType)
-		}
 
 		// emit type structs for error and func(error) string.
 		// The latter is the type of an auto-generated wrapper.

src/cmd/compile/internal/typecheck/iexport.go

@@ -607,7 +607,7 @@ func (p *iexporter) doDecl(n *ir.Name) {
 			// Do same for ComparableType as for ErrorType.
 			underlying = types.ComparableType
 		}
-		if base.Flag.G > 0 && underlying == types.AnyType.Underlying() {
+		if underlying == types.AnyType.Underlying() {
 			// Do same for AnyType as for ErrorType.
 			underlying = types.AnyType
 		}
@@ -949,7 +949,6 @@ func (w *exportWriter) startType(k itag) {
 func (w *exportWriter) doTyp(t *types.Type) {
 	s := t.Sym()
 	if s != nil && t.OrigSym() != nil {
-		assert(base.Flag.G > 0)
 		// This is an instantiated type - could be a re-instantiation like
 		// Value[T2] or a full instantiation like Value[int].
 		if strings.Index(s.Name, "[") < 0 {
@@ -974,7 +973,6 @@ func (w *exportWriter) doTyp(t *types.Type) {
 	// type, rather than a defined type with typeparam underlying type, like:
 	// type orderedAbs[T any] T
 	if t.IsTypeParam() && t.Underlying() == t {
-		assert(base.Flag.G > 0)
 		if s.Pkg == types.BuiltinPkg || s.Pkg == types.UnsafePkg {
 			base.Fatalf("builtin type missing from typIndex: %v", t)
 		}
@@ -1064,7 +1062,6 @@ func (w *exportWriter) doTyp(t *types.Type) {
 		}
 
 	case types.TUNION:
-		assert(base.Flag.G > 0)
 		// TODO(danscales): possibly put out the tilde bools in more
 		// compact form.
 		w.startType(unionType)

src/cmd/compile/internal/types/universe.go

@@ -115,10 +115,6 @@ func InitTypes(defTypeName func(sym *Sym, typ *Type) Object) {
 	AnyType.SetUnderlying(NewInterface(BuiltinPkg, []*Field{}, false))
 	ResumeCheckSize()
 
-	if base.Flag.G == 0 {
-		ComparableType.Sym().Def = nil
-	}
-
 	Types[TUNSAFEPTR] = defBasic(TUNSAFEPTR, UnsafePkg, "Pointer")
 
 	Types[TBLANK] = newType(TBLANK)