compiler: support all kinds of recursive types

Previously we only supported recursive types in structs. But there can
be other kinds of recursive types, like slices:

    type RecursiveSlice []RecursiveSlice

This doesn't involve structs, so it led to infinite recursion in the
compiler. This fix avoids recursion at the proper level: at the place
where the named type is defined.

compiler/compiler.go

@@ -569,10 +569,19 @@ func (c *compilerContext) createDIType(typ types.Type) llvm.Metadata {
 	case *types.Map:
 		return c.getDIType(types.NewPointer(c.program.ImportedPackage("runtime").Members["hashmap"].(*ssa.Type).Type()))
 	case *types.Named:
-		return c.dibuilder.CreateTypedef(llvm.DITypedef{
+		// Placeholder metadata node, to be replaced afterwards.
+		temporaryMDNode := c.dibuilder.CreateReplaceableCompositeType(llvm.Metadata{}, llvm.DIReplaceableCompositeType{
+			Tag:         dwarf.TagTypedef,
+			SizeInBits:  sizeInBytes * 8,
+			AlignInBits: uint32(c.targetData.ABITypeAlignment(llvmType)) * 8,
+		})
+		c.ditypes[typ] = temporaryMDNode
+		md := c.dibuilder.CreateTypedef(llvm.DITypedef{
 			Type: c.getDIType(typ.Underlying()),
 			Name: typ.String(),
 		})
+		temporaryMDNode.ReplaceAllUsesWith(md)
+		return md
 	case *types.Pointer:
 		return c.dibuilder.CreatePointerType(llvm.DIPointerType{
 			Pointee:      c.getDIType(typ.Elem()),
@@ -634,13 +643,6 @@ func (c *compilerContext) createDIType(typ types.Type) llvm.Metadata {
 			},
 		})
 	case *types.Struct:
-		// Placeholder metadata node, to be replaced afterwards.
-		temporaryMDNode := c.dibuilder.CreateReplaceableCompositeType(llvm.Metadata{}, llvm.DIReplaceableCompositeType{
-			Tag:         dwarf.TagStructType,
-			SizeInBits:  sizeInBytes * 8,
-			AlignInBits: uint32(c.targetData.ABITypeAlignment(llvmType)) * 8,
-		})
-		c.ditypes[typ] = temporaryMDNode
 		elements := make([]llvm.Metadata, typ.NumFields())
 		for i := range elements {
 			field := typ.Field(i)
@@ -659,7 +661,6 @@ func (c *compilerContext) createDIType(typ types.Type) llvm.Metadata {
 			AlignInBits: uint32(c.targetData.ABITypeAlignment(llvmType)) * 8,
 			Elements:    elements,
 		})
-		temporaryMDNode.ReplaceAllUsesWith(md)
 		return md
 	case *types.TypeParam:
 		return c.getDIType(typ.Underlying())

testdata/slice.go

@@ -6,6 +6,8 @@ type MySlice [32]byte
 
 type myUint8 uint8
 
+type RecursiveSlice []RecursiveSlice
+
 // Indexing into slice with named type (regression test).
 var array = [4]int{
 	myUint8(2): 3,
@@ -160,6 +162,10 @@ func main() {
 	for _, c := range named {
 		assert(c == 0)
 	}
+
+	// Test recursive slices.
+	rs := []RecursiveSlice(nil)
+	println("len:", len(rs))
 }
 
 func printslice(name string, s []int) {

testdata/slice.txt

@@ -16,3 +16,4 @@ bytes: len=6 cap=6 data: 1 2 3 102 111 111
 slice to array pointer: 1 -2 20 4
 unsafe.Add array: 1 5 8 4
 unsafe.Slice array: 3 3 9 15 4
+len: 0