cmd/compile: fix any in -G=0 mode

Fixes go test -gcflags=all=-G=0 -short std,
except for the packages with generics in their tests
(constraints, encoding/xml), and except for the
go/internal/gcimporter and go/types tests,
because the compiler does not preserve any
in its -G=0 export information.
(That's probably acceptable for now.)

Fixes cd test/; GO_BUILDER_NAME=longtest go run run.go
completely, which should fix the longtest builder.

Fixes #50159.

Change-Id: I9390972239c18831833edd6530191da2842b876b
Reviewed-on: https://go-review.googlesource.com/c/go/+/371715
Trust: Russ Cox <[email protected]>
Run-TryBot: Russ Cox <[email protected]>
Reviewed-by: Cherry Mui <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

Author: rsc

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

@@ -57,7 +57,7 @@ func InitTypes(defTypeName func(sym *Sym, typ *Type) Object) {
 		SimType[et] = et
 	}
 
-	Types[TANY] = newType(TANY)
+	Types[TANY] = newType(TANY) // note: an old placeholder type, NOT the new builtin 'any' alias for interface{}
 	Types[TINTER] = NewInterface(LocalPkg, nil, false)
 	CheckSize(Types[TINTER])
 
@@ -91,6 +91,7 @@ func InitTypes(defTypeName func(sym *Sym, typ *Type) Object) {
 	// int32  Hence, (bytetype|runtype).Sym.isAlias() is false.
 	// TODO(gri) Should we get rid of this special case (at the cost
 	// of less informative error messages involving bytes and runes)?
+	// NOTE(rsc): No, the error message quality is important.
 	// (Alternatively, we could introduce an OTALIAS node representing
 	// type aliases, albeit at the cost of having to deal with it everywhere).
 	ByteType = defBasic(TUINT8, BuiltinPkg, "byte")
@@ -111,12 +112,11 @@ func InitTypes(defTypeName func(sym *Sym, typ *Type) Object) {
 	// any type (interface)
 	DeferCheckSize()
 	AnyType = defBasic(TFORW, BuiltinPkg, "any")
-	AnyType.SetUnderlying(NewInterface(NoPkg, []*Field{}, false))
+	AnyType.SetUnderlying(NewInterface(BuiltinPkg, []*Field{}, false))
 	ResumeCheckSize()
 
 	if base.Flag.G == 0 {
 		ComparableType.Sym().Def = nil
-		AnyType.Sym().Def = nil
 	}
 
 	Types[TUNSAFEPTR] = defBasic(TUNSAFEPTR, UnsafePkg, "Pointer")