cmd/compile: report channel size errors correctly for -G=3

First, we need to set base.Pos in varDecl() and typeDecl(), so it will
be correct if we need to report type size errors while converting types.
Changed error calls in types/sizes.go to use Errorf, not ErrorfAt, since
we want to use base.Pos (which will set from t.Pos(), if that is
available).

Second, we need to add an extra call CalcSize(t1.Elem()) in the
TCHANARGS case of CalcSize(). We can use CalcSize() rather than
CheckSize(), since we know the top-level recursive type will have been
calculated by the time we process the fake TCHANARGS type. In -G=0 mode,
the size of the channel element has often been calculated because of
some other processing (but not in the case of #49767). But in -G=3 mode,
we just calculate sizes during the single noder2 pass, so we are more
likely to have not gotten to calculating the size of the element yet,
depending on the order of processing of the deferredTypeStack.

Fixes the tests fixedbugs/issue{42058a,42058b}.go that were
disabled for -G=3 mode.

Had to add exceptions in stdlib_test.go for go/types and types2, because
the types2 typechecker does not know about type size limits.

Fixes #49814
Fixes #49771
Updates #49767

Change-Id: I77d058e8ceff68a58c4c386a8cf46799c54b04c3
Reviewed-on: https://go-review.googlesource.com/c/go/+/367955
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

3 files changed, 16 insertions, 5 deletions

diff --git a/src/cmd/compile/internal/noder/decl.go b/src/cmd/compile/internal/noder/decl.go
index 027c8598fd..b7fd95e2e8 100644
--- a/src/cmd/compile/internal/noder/decl.go
+++ b/src/cmd/compile/internal/noder/decl.go
@@ -160,6 +160,8 @@ func (g *irgen) funcDecl(out *ir.Nodes, decl *syntax.FuncDecl) {
 }
 
 func (g *irgen) typeDecl(out *ir.Nodes, decl *syntax.TypeDecl) {
+	// Set the position for any error messages we might print (e.g. too large types).
+	base.Pos = g.pos(decl)
 	assert(g.curDecl == "")
 	// Set g.curDecl to the type name, as context for the type params declared
 	// during types2-to-types1 translation if this is a generic type.
@@ -244,6 +246,8 @@ func (g *irgen) typeDecl(out *ir.Nodes, decl *syntax.TypeDecl) {
 
 func (g *irgen) varDecl(out *ir.Nodes, decl *syntax.VarDecl) {
 	pos := g.pos(decl)
+	// Set the position for any error messages we might print (e.g. too large types).
+	base.Pos = pos
 	names := make([]*ir.Name, len(decl.NameList))
 	for i, name := range decl.NameList {
 		names[i], _ = g.def(name)
diff --git a/src/cmd/compile/internal/types/size.go b/src/cmd/compile/internal/types/size.go
index 0f3db06c1d..fb6accdc64 100644
--- a/src/cmd/compile/internal/types/size.go
+++ b/src/cmd/compile/internal/types/size.go
@@ -450,16 +450,21 @@ func CalcSize(t *Type) {
 
 		CheckSize(t.Elem())
 
-		// make fake type to check later to
-		// trigger channel argument check.
+		// Make fake type to trigger channel element size check after
+		// any top-level recursive type has been completed.
 		t1 := NewChanArgs(t)
 		CheckSize(t1)
 
 	case TCHANARGS:
 		t1 := t.ChanArgs()
 		CalcSize(t1) // just in case
+		// Make sure size of t1.Elem() is calculated at this point. We can
+		// use CalcSize() here rather than CheckSize(), because the top-level
+		// (possibly recursive) type will have been calculated before the fake
+		// chanargs is handled.
+		CalcSize(t1.Elem())
 		if t1.Elem().width >= 1<<16 {
-			base.ErrorfAt(typePos(t1), "channel element type too large (>64kB)")
+			base.Errorf("channel element type too large (>64kB)")
 		}
 		w = 1 // anything will do
 
@@ -492,7 +497,7 @@ func CalcSize(t *Type) {
 		if t.Elem().width != 0 {
 			cap := (uint64(MaxWidth) - 1) / uint64(t.Elem().width)
 			if uint64(t.NumElem()) > cap {
-				base.ErrorfAt(typePos(t), "type %L larger than address space", t)
+				base.Errorf("type %L larger than address space", t)
 			}
 		}
 		w = t.NumElem() * t.Elem().width
@@ -539,7 +544,7 @@ func CalcSize(t *Type) {
 	}
 
 	if PtrSize == 4 && w != int64(int32(w)) {
-		base.ErrorfAt(typePos(t), "type %v too large", t)
+		base.Errorf("type %v too large", t)
 	}
 
 	t.width = w
diff --git a/src/cmd/compile/internal/types2/stdlib_test.go b/src/cmd/compile/internal/types2/stdlib_test.go
index 9c22f01673..5ac01ac253 100644
--- a/src/cmd/compile/internal/types2/stdlib_test.go
+++ b/src/cmd/compile/internal/types2/stdlib_test.go
@@ -194,6 +194,8 @@ func TestStdFixed(t *testing.T) {
 		"issue42058b.go", // types2 does not have constraints on channel element size
 		"issue48097.go",  // go/types doesn't check validity of //go:xxx directives, and non-init bodyless function
 		"issue48230.go",  // go/types doesn't check validity of //go:xxx directives
+		"issue49767.go",  // go/types does not have constraints on channel element size
+		"issue49814.go",  // go/types does not have constraints on array size
 	)
 }