cmd/compile: simplify {defer,resume}checkwidth logic

This CL extends {defer,resume}checkwidth to support nesting, which
simplifies usage.

Updates #33658.

Change-Id: Ib3ffb8a7cabfae2cbeba74e21748c228436f4726
Reviewed-on: https://go-review.googlesource.com/c/go/+/192721
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Robert Griesemer <gri@golang.org>

src/cmd/compile/internal/gc/align.go

@@ -217,7 +217,7 @@ func dowidth(t *types.Type) {
 	}
 
 	// defer checkwidth calls until after we're done
-	defercalc++
+	defercheckwidth()
 
 	lno := lineno
 	if asNode(t.Nod) != nil {
@@ -391,11 +391,7 @@ func dowidth(t *types.Type) {
 
 	lineno = lno
 
-	if defercalc == 1 {
 	resumecheckwidth()
-	} else {
-		defercalc--
-	}
 }
 
 // when a type's width should be known, we call checkwidth
@@ -440,24 +436,18 @@ func checkwidth(t *types.Type) {
 }
 
 func defercheckwidth() {
-	// we get out of sync on syntax errors, so don't be pedantic.
+	defercalc++
-	if defercalc != 0 && nerrors == 0 {
-		Fatalf("defercheckwidth")
-	}
-	defercalc = 1
 }
 
 func resumecheckwidth() {
-	if defercalc == 0 {
+	if defercalc == 1 {
-		Fatalf("resumecheckwidth")
-	}
-
 		for len(deferredTypeStack) > 0 {
 			t := deferredTypeStack[len(deferredTypeStack)-1]
 			deferredTypeStack = deferredTypeStack[:len(deferredTypeStack)-1]
 			t.SetDeferwidth(false)
 			dowidth(t)
 		}
+	}
 
-	defercalc = 0
+	defercalc--
 }

src/cmd/compile/internal/gc/iimport.go

@@ -298,21 +298,10 @@ func (r *importReader) doDecl(n *Node) {
 
 		// We also need to defer width calculations until
 		// after the underlying type has been assigned.
-		//
-		// TODO(mdempsky): Add nesting support directly to
-		// {defer,resume}checkwidth? Width calculations are
-		// already deferred during initial typechecking, but
-		// not when we're expanding inline function bodies, so
-		// we currently need to handle both cases here.
-		deferring := defercalc != 0
-		if !deferring {
 		defercheckwidth()
-		}
 		underlying := r.typ()
 		copytype(typenod(t), underlying)
-		if !deferring {
 		resumecheckwidth()
-		}
 
 		if underlying.IsInterface() {
 			break

src/cmd/compile/internal/gc/main.go

@@ -527,7 +527,6 @@ func Main(archInit func(*Arch)) {
 	//   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.
-	defercheckwidth()
 
 	// Don't use range--typecheck can add closures to xtop.
 	timings.Start("fe", "typecheck", "top1")
@@ -549,7 +548,6 @@ func Main(archInit func(*Arch)) {
 			xtop[i] = typecheck(n, ctxStmt)
 		}
 	}
-	resumecheckwidth()
 
 	// Phase 3: Type check function bodies.
 	// Don't use range--typecheck can add closures to xtop.
@@ -1035,7 +1033,6 @@ func loadsys() {
 
 	inimport = true
 	typecheckok = true
-	defercheckwidth()
 
 	typs := runtimeTypes()
 	for _, d := range runtimeDecls {
@@ -1052,7 +1049,6 @@ func loadsys() {
 	}
 
 	typecheckok = false
-	resumecheckwidth()
 	inimport = false
 }
 

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

@@ -3669,9 +3669,7 @@ func typecheckdef(n *Node) {
 		}
 
 		// regular type declaration
-		if Curfn != nil {
 		defercheckwidth()
-		}
 		n.SetWalkdef(1)
 		setTypeNode(n, types.New(TFORW))
 		n.Type.Sym = n.Sym
@@ -3682,10 +3680,8 @@ func typecheckdef(n *Node) {
 			// but it was reported. Silence future errors.
 			n.Type.SetBroke(true)
 		}
-		if Curfn != nil {
 		resumecheckwidth()
 	}
-	}
 
 ret:
 	if n.Op != OLITERAL && n.Type != nil && n.Type.IsUntyped() {

test/fixedbugs/bug195.go

@@ -18,10 +18,10 @@ type I4 interface { // GC_ERROR "invalid recursive type"
 	I4	// GCCGO_ERROR "interface"
 }
 
-type I5 interface {
+type I5 interface { // GC_ERROR "invalid recursive type"
 	I6	// GCCGO_ERROR "interface"
 }
 
-type I6 interface { // GC_ERROR "invalid recursive type"
+type I6 interface {
 	I5	// GCCGO_ERROR "interface"
 }

test/fixedbugs/issue23823.go

@@ -6,10 +6,10 @@
 
 package p
 
-type I1 = interface { // ERROR "invalid recursive type"
+type I1 = interface {
 	I2
 }
 
-type I2 interface {
+type I2 interface { // ERROR "invalid recursive type"
 	I1
 }