Two fixes to type cast evaluation (go-delve#3186)

* proc: allow casts form unsafe.Pointer to any pointer and vice versa

We've allowed doing this with uintptr but we should allow
unsafe.Pointer to be used like Go uses it.

* proc: fix type casts to ptr-to-ptr types

Fix type casts to **type.

pkg/proc/eval.go

@@ -739,9 +739,14 @@ func (scope *EvalScope) evalTypeCastOrFuncCall(node *ast.CallExpr) (*Variable, e
 		return v, err
 	}
 
-	fnnode := removeParen(node.Fun)
-	if n, _ := fnnode.(*ast.StarExpr); n != nil {
-		fnnode = removeParen(n.X)
+	fnnode := node.Fun
+	for {
+		fnnode = removeParen(fnnode)
+		n, _ := fnnode.(*ast.StarExpr)
+		if n == nil {
+			break
+		}
+		fnnode = n.X
 	}
 
 	switch n := fnnode.(type) {
@@ -811,6 +816,11 @@ func (scope *EvalScope) evalTypeCast(node *ast.CallExpr) (*Variable, error) {
 
 	// compatible underlying types
 	if typeCastCompatibleTypes(argv.RealType, typ) {
+		if ptyp, isptr := typ.(*godwarf.PtrType); argv.Kind == reflect.Ptr && argv.loaded && len(argv.Children) > 0 && isptr {
+			cv := argv.Children[0]
+			argv.Children[0] = *newVariable(cv.Name, cv.Addr, ptyp.Type, cv.bi, cv.mem)
+			argv.Children[0].OnlyAddr = true
+		}
 		argv.RealType = typ
 		argv.DwarfType = styp
 		return argv, nil
@@ -1028,6 +1038,11 @@ func typeCastCompatibleTypes(typ1, typ2 godwarf.Type) bool {
 	switch ttyp1 := typ1.(type) {
 	case *godwarf.PtrType:
 		if ttyp2, ok := typ2.(*godwarf.PtrType); ok {
+			_, isvoid1 := ttyp1.Type.(*godwarf.VoidType)
+			_, isvoid2 := ttyp2.Type.(*godwarf.VoidType)
+			if isvoid1 || isvoid2 {
+				return true
+			}
 			// pointer types are compatible if their element types are compatible
 			return typeCastCompatibleTypes(resolveTypedef(ttyp1.Type), resolveTypedef(ttyp2.Type))
 		}

pkg/proc/variables_test.go

@@ -820,6 +820,15 @@ func TestEvalExpression(t *testing.T) {
 		{`(*string)(&typedstringvar)`, false, `(*string)(…`, `(*string)(…`, "*string", nil},
 		{`(*main.astruct)(&namedA1)`, false, `(*main.astruct)(…`, `(*main.astruct)(…`, "*main.astruct", nil},
 		{`(*main.astructName2)(&namedA1)`, false, `(*main.astructName2)(…`, `(*main.astructName2)(…`, "*main.astructName2", nil},
+
+		// Conversions to and from uintptr/unsafe.Pointer
+		{`*(*uint)(uintptr(p1))`, false, `1`, `1`, "uint", nil},
+		{`*(*uint)(uintptr(&i1))`, false, `1`, `1`, "uint", nil},
+		{`*(*uint)(unsafe.Pointer(p1))`, false, `1`, `1`, "uint", nil},
+		{`*(*uint)(unsafe.Pointer(&i1))`, false, `1`, `1`, "uint", nil},
+
+		// Conversions to ptr-to-ptr types
+		{`**(**runtime.hmap)(uintptr(&m1))`, false, `…`, `…`, "runtime.hmap", nil},
 	}
 
 	ver, _ := goversion.Parse(runtime.Version())