go/ssa: update public doc of CreatePackage

Change-Id: I6ae61513717bac0bd756b612f0a843d55f1df296
GitHub-Last-Rev: 734464cdb3
GitHub-Pull-Request: golang/tools#520
Reviewed-on: https://go-review.googlesource.com/c/tools/+/613159
Reviewed-by: Carlos Amedee <carlos@golang.org>
Reviewed-by: Tim King <taking@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>

go/ssa/create.go

@@ -193,11 +193,7 @@ func membersFromDecl(pkg *Package, decl ast.Decl, goversion string) {
 //
 // The real work of building SSA form for each function is not done
 // until a subsequent call to Package.Build.
-//
-// CreatePackage should not be called after building any package in
-// the program.
 func (prog *Program) CreatePackage(pkg *types.Package, files []*ast.File, info *types.Info, importable bool) *Package {
-	// TODO(adonovan): assert that no package has yet been built.
 	if pkg == nil {
 		panic("nil pkg") // otherwise pkg.Scope below returns types.Universe!
 	}

go/ssa/ssa.go

@@ -342,7 +342,7 @@ type Function struct {
 	// source information
 	Synthetic string      // provenance of synthetic function; "" for true source functions
 	syntax    ast.Node    // *ast.Func{Decl,Lit}, if from syntax (incl. generic instances) or (*ast.RangeStmt if a yield function)
-	info      *types.Info // type annotations (iff syntax != nil)
+	info      *types.Info // type annotations (if syntax != nil)
 	goversion string      // Go version of syntax (NB: init is special)
 
 	parent *Function // enclosing function if anon; nil if global