From 0b64e2190ff5afc141991f9f8004f0b813a0121b Mon Sep 17 00:00:00 2001
From: Emily Hudson <emily33901@gmail.com>
Date: Wed, 27 May 2020 13:47:38 +0100
Subject: [PATCH] checker,cgen: unpack multi returns in return statements

---
 vlib/v/checker/checker.v | 15 +++++++++--
 vlib/v/gen/cgen.v        | 54 +++++++++++++++++++++++++++++++++++++++-
 2 files changed, 66 insertions(+), 3 deletions(-)

diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index 524af0d416..3d61ee1a54 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -1167,17 +1167,28 @@ pub fn (mut c Checker) return_stmt(mut return_stmt ast.Return) {
 	mut got_types := []table.Type{}
 	for expr in return_stmt.exprs {
 		typ := c.expr(expr)
-		got_types << typ
+
+		// Unpack multi return types
+		sym :=  c.table.get_type_symbol(typ)
+		if sym.kind == .multi_return {
+			for t in sym.mr_info().types {
+				got_types << t
+			} 
+		} else {
+			got_types << typ
+		}
 	}
 	return_stmt.types = got_types
 	// allow `none` & `error (Option)` return types for function that returns optional
 	if exp_is_optional && got_types[0].idx() in [table.none_type_idx, c.table.type_idxs['Option']] {
 		return
 	}
+
 	if expected_types.len > 0 && expected_types.len != got_types.len {
-		// c.error('wrong number of return arguments:\n\texpected: $expected_table.str()\n\tgot: $got_types.str()', return_stmt.pos)
 		c.error('wrong number of return arguments', return_stmt.pos)
+		return
 	}
+
 	for i, exp_type in expected_types {
 		got_typ := got_types[i]
 		is_generic := exp_type == table.t_type
diff --git a/vlib/v/gen/cgen.v b/vlib/v/gen/cgen.v
index 657fb6d1f8..1c3f84dc72 100644
--- a/vlib/v/gen/cgen.v
+++ b/vlib/v/gen/cgen.v
@@ -2191,6 +2191,19 @@ fn (mut g Gen) index_expr(node ast.IndexExpr) {
 	}
 }
 
+[inline]
+fn (g Gen) expr_is_multi_return_call(expr ast.Expr) bool {
+	match expr {
+		ast.CallExpr {
+			return g.table.get_type_symbol(it.return_type).kind == .multi_return
+		}
+		else {
+			return false
+		}
+	} 
+
+}
+
 fn (mut g Gen) return_statement(node ast.Return) {
 	g.write('return ')
 	if g.fn_decl.name == 'main' {
@@ -2226,18 +2239,57 @@ fn (mut g Gen) return_statement(node ast.Return) {
 		} else {
 			styp = g.typ(g.fn_decl.return_type)
 		}
+
+		// Use this to keep the tmp assignments in order
+		mut multi_unpack := ''
+
+
 		g.write('($styp){')
+		
+		mut arg_idx := 0
 		for i, expr in node.exprs {
-			g.write('.arg$i=')
+			// Check if we are dealing with a multi return and handle it seperately
+			if g.expr_is_multi_return_call(expr) {
+				c := expr as ast.CallExpr
+				expr_sym := g.table.get_type_symbol(c.return_type)
+
+				// Create a tmp for this call
+				tmp := g.new_tmp_var()
+				s := g.go_before_stmt(0)
+				expr_styp := g.typ(c.return_type)
+				g.write('$expr_styp $tmp=')
+				g.expr(expr)
+				g.writeln(';')
+				multi_unpack += g.go_before_stmt(0)
+				g.write(s)
+
+				expr_types := expr_sym.mr_info().types
+				for j, _ in expr_types {
+					g.write('.arg$arg_idx=${tmp}.arg$j')
+					if j < expr_types.len || i < node.exprs.len - 1 {
+						g.write(',')
+					}
+					arg_idx++
+				}
+
+				continue
+			}
+
+			g.write('.arg$arg_idx=')
 			g.expr(expr)
+			arg_idx++
 			if i < node.exprs.len - 1 {
 				g.write(',')
 			}
 		}
 		g.write('}')
+
 		if fn_return_is_optional {
 			g.write(' }, sizeof($styp))')
 		}
+
+		// Make sure to add our unpacks
+		g.insert_before_stmt(multi_unpack)
 	} else if node.exprs.len >= 1 {
 		// normal return
 		return_sym := g.table.get_type_symbol(node.types[0])