From e0f9c042c1341fd55a7771eda947df33cd42e5d5 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Sat, 25 Apr 2020 21:24:04 +0200
Subject: [PATCH] cgen: interface fixes

---
 cmd/tools/vtest-fixed.v       |  1 -
 vlib/v/gen/cgen.v             | 12 ++++++------
 vlib/v/gen/fn.v               | 33 ++++++++++++++++++++++++++++++---
 vlib/v/tests/interface_test.v |  7 +++----
 4 files changed, 39 insertions(+), 14 deletions(-)

diff --git a/cmd/tools/vtest-fixed.v b/cmd/tools/vtest-fixed.v
index 77f468313b..511284fe82 100644
--- a/cmd/tools/vtest-fixed.v
+++ b/cmd/tools/vtest-fixed.v
@@ -16,7 +16,6 @@ const (
 		'vlib/v/tests/num_lit_call_method_test.v',
 		'vlib/v/tests/pointers_test.v',
 		'vlib/v/tests/type_test.v',
-		'vlib/v/tests/interface_test.v',
 		'vlib/v/tests/valgrind/valgrind_test.v', // ubuntu-musl only
 		'vlib/v/tests/pointers_str_test.v',
 		'vlib/net/http/cookie_test.v',
diff --git a/vlib/v/gen/cgen.v b/vlib/v/gen/cgen.v
index 8375788057..d5e6b1a1be 100644
--- a/vlib/v/gen/cgen.v
+++ b/vlib/v/gen/cgen.v
@@ -573,11 +573,11 @@ fn (mut g Gen) stmt(node ast.Stmt) {
 		}
 		ast.Import {}
 		ast.InterfaceDecl {
-			g.writeln('//interface')
-			g.writeln('typedef struct {')
-			g.writeln('\tvoid* _object;')
-			g.writeln('\tint _interface_idx;')
-			g.writeln('} $it.name;')
+			g.definitions.writeln('//interface')
+			g.definitions.writeln('typedef struct {')
+			g.definitions.writeln('\tvoid* _object;')
+			g.definitions.writeln('\tint _interface_idx;')
+			g.definitions.writeln('} $it.name;')
 		}
 		ast.Module {}
 		ast.Return {
@@ -1301,7 +1301,7 @@ fn (mut g Gen) assign_expr(node ast.AssignExpr) {
 				g.write(', ')
 			}
 			g.is_assign_lhs = false
-			//right_sym := g.table.get_type_symbol(node.right_type)
+			// right_sym := g.table.get_type_symbol(node.right_type)
 			// left_sym := g.table.get_type_symbol(node.left_type)
 			mut cloned := false
 			// !g.is_array_set
diff --git a/vlib/v/gen/fn.v b/vlib/v/gen/fn.v
index b0c9ee5f78..791cc44a35 100644
--- a/vlib/v/gen/fn.v
+++ b/vlib/v/gen/fn.v
@@ -249,11 +249,22 @@ fn (mut g Gen) method_call(node ast.CallExpr) {
 	typ_sym := g.table.get_type_symbol(node.receiver_type)
 	mut receiver_name := typ_sym.name
 	if typ_sym.kind == .interface_ {
+		// Find the index of the method
+		mut idx := -1
+		for i, method in typ_sym.methods {
+			if method.name == node.name {
+				idx = i
+			}
+		}
+		if idx == -1 {
+			verror('method_call: cannot find interface method index')
+		}
+		sret_type := g.typ(node.return_type)
 		g.writeln('// interface method call')
 		// `((void (*)())(Speaker_name_table[s._interface_idx][1]))(s._object);`
-		g.write('((void (*)())(${receiver_name}_name_table[')
+		g.write('(($sret_type (*)())(${receiver_name}_name_table[')
 		g.expr(node.left)
-		g.write('._interface_idx][1]))(')
+		g.write('._interface_idx][$idx]))(')
 		g.expr(node.left)
 		g.write('._object)')
 		return
@@ -443,17 +454,33 @@ fn (mut g Gen) call_args(args []ast.CallArg, expected_types []table.Type) {
 	is_forwarding_varg := args.len > 0 && args[args.len - 1].typ.flag_is(.variadic)
 	gen_vargs := is_variadic && !is_forwarding_varg
 	mut arg_no := 0
-	for arg in args {
+	for i, arg in args {
 		if gen_vargs && arg_no == expected_types.len - 1 {
 			break
 		}
+		// if arg.typ.name.starts_with('I') {
+		// }
+		mut is_interface := false
 		// some c fn definitions dont have args (cfns.v) or are not updated in checker
 		// when these are fixed we wont need this check
 		if arg_no < expected_types.len {
+			if expected_types[arg_no] != 0 {
+				// Cast a type to interface
+				// `foo(dog)` => `foo(I_Dog_to_Animal(dog))`
+				exp_sym := g.table.get_type_symbol(expected_types[arg_no])
+				sym := g.table.get_type_symbol(arg.typ)
+				if exp_sym.kind == .interface_ {
+					g.write('I_${sym.name}_to_${exp_sym.name}(')
+					is_interface = true
+				}
+			}
 			g.ref_or_deref_arg(arg, expected_types[arg_no])
 		} else {
 			g.expr(arg.expr)
 		}
+		if is_interface {
+			g.write(')')
+		}
 		if arg_no < args.len - 1 || gen_vargs {
 			g.write(', ')
 		}
diff --git a/vlib/v/tests/interface_test.v b/vlib/v/tests/interface_test.v
index 0a365e9bb1..efa34997d7 100644
--- a/vlib/v/tests/interface_test.v
+++ b/vlib/v/tests/interface_test.v
@@ -36,10 +36,8 @@ interface Speaker {
 fn perform_speak(s Speaker) {
 	s.speak()
 	assert true
-	/*
 	name := s.name()
        assert name == 'Dog' || name == 'Cat'
-*/
        println(s.name())
 }
 
@@ -48,7 +46,7 @@ fn test_perform_speak() {
 	perform_speak(dog)
 	cat := Cat{}
 	perform_speak(cat)
-	// perform_speakers([dog, cat])
+	//perform_speakers([dog, cat])
 	/*
 	f := Foo {
 		speaker: dog
@@ -56,6 +54,8 @@ fn test_perform_speak() {
 */
 }
 
+//fn perform_speakers(speakers []Speaker) {}
+
 /*
 interface Speak2er {
 	name ()string
@@ -67,7 +67,6 @@ struct Foo {
 	speakers []Speaker
 }
 
-fn perform_speakers(speakers []Speaker) {}
 
 
 interface Register {