From 44502a3fb2f43ca3ddab33a18ee0d286217248dd Mon Sep 17 00:00:00 2001
From: Tanel Liiv <204019+dkull@users.noreply.github.com>
Date: Sat, 16 May 2020 00:14:53 +0300
Subject: [PATCH] parser: return multi expr

---
 vlib/v/ast/ast.v                   |   2 +
 vlib/v/checker/checker.v           |  34 +++++++--
 vlib/v/gen/cgen.v                  |  49 ++++++++----
 vlib/v/parser/assign.v             |  50 +++++-------
 vlib/v/parser/parser.v             | 119 ++++++++++++++++++++++-------
 vlib/v/parser/pratt.v              |   3 +
 vlib/v/tests/complex_assign_test.v |  59 ++++++++++++--
 7 files changed, 231 insertions(+), 85 deletions(-)

diff --git a/vlib/v/ast/ast.v b/vlib/v/ast/ast.v
index 95dfb04baf..bc17664c23 100644
--- a/vlib/v/ast/ast.v
+++ b/vlib/v/ast/ast.v
@@ -755,6 +755,8 @@ pub:
 pub struct ConcatExpr {
 pub:
 	vals []Expr
+pub mut:
+	return_type table.Type
 }
 
 pub struct None {
diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index feed2eb30a..a5097eb501 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -1588,6 +1588,13 @@ fn (mut c Checker) stmts(stmts []ast.Stmt) {
 
 pub fn (mut c Checker) expr(node ast.Expr) table.Type {
 	match mut node {
+		ast.AnonFn {
+			keep_ret_type := c.fn_return_type
+			c.fn_return_type = it.decl.return_type
+			c.stmts(it.decl.stmts)
+			c.fn_return_type = keep_ret_type
+			return it.typ
+		}
 		ast.ArrayInit {
 			return c.array_init(mut it)
 		}
@@ -1645,6 +1652,9 @@ pub fn (mut c Checker) expr(node ast.Expr) table.Type {
 		ast.CharLiteral {
 			return table.byte_type
 		}
+		ast.ConcatExpr {
+			return c.concat_expr(mut it)
+		}
 		ast.EnumVal {
 			return c.enum_val(mut it)
 		}
@@ -1730,13 +1740,6 @@ pub fn (mut c Checker) expr(node ast.Expr) table.Type {
 			it.expr_type = c.expr(it.expr)
 			return table.string_type
 		}
-		ast.AnonFn {
-			keep_ret_type := c.fn_return_type
-			c.fn_return_type = it.decl.return_type
-			c.stmts(it.decl.stmts)
-			c.fn_return_type = keep_ret_type
-			return it.typ
-		}
 		else {
 			tnode := typeof(node)
 			if tnode != 'unknown v.ast.Expr' {
@@ -1858,6 +1861,23 @@ pub fn (mut c Checker) ident(mut ident ast.Ident) table.Type {
 	return table.void_type
 }
 
+pub fn (mut c Checker) concat_expr(concat_expr mut ast.ConcatExpr) table.Type {
+	mut mr_types := []table.Type{}
+	for expr in concat_expr.vals {
+		mr_types << c.expr(expr)
+	}
+	if concat_expr.vals.len == 1 {
+		typ := mr_types[0]
+		concat_expr.return_type = typ
+		return typ
+	} else {
+		typ := c.table.find_or_register_multi_return(mr_types)
+		table.new_type(typ)
+		concat_expr.return_type = typ
+		return typ
+	}
+}
+
 pub fn (mut c Checker) match_expr(mut node ast.MatchExpr) table.Type {
 	node.is_expr = c.expected_type != table.void_type
 	node.expected_type = c.expected_type
diff --git a/vlib/v/gen/cgen.v b/vlib/v/gen/cgen.v
index c66b0857d2..ccf87e0434 100644
--- a/vlib/v/gen/cgen.v
+++ b/vlib/v/gen/cgen.v
@@ -1163,6 +1163,18 @@ fn (g &Gen) autofree_var_call(free_fn_name string, v ast.Var) string {
 fn (mut g Gen) expr(node ast.Expr) {
 	// println('cgen expr() line_nr=$node.pos.line_nr')
 	match node {
+		ast.AnonFn {
+			// TODO: dont fiddle with buffers
+			pos := g.out.len
+			def_pos := g.definitions.len
+			g.stmt(it.decl)
+			fn_body := g.out.after(pos)
+			g.out.go_back(fn_body.len)
+			g.definitions.go_back(g.definitions.len - def_pos)
+			g.definitions.write(fn_body)
+			fsym := g.table.get_type_symbol(it.typ)
+			g.write('&${fsym.name}')
+		}
 		ast.ArrayInit {
 			g.array_init(it)
 		}
@@ -1226,6 +1238,9 @@ fn (mut g Gen) expr(node ast.Expr) {
 		ast.CharLiteral {
 			g.write("'$it.val'")
 		}
+		ast.ConcatExpr {
+			g.concat_expr(it)	
+		}
 		ast.EnumVal {
 			// g.write('${it.mod}${it.enum_name}_$it.val')
 			styp := g.typ(it.typ)
@@ -1375,18 +1390,6 @@ fn (mut g Gen) expr(node ast.Expr) {
 		ast.TypeOf {
 			g.typeof_expr(it)
 		}
-		ast.AnonFn {
-			// TODO: dont fiddle with buffers
-			pos := g.out.len
-			def_pos := g.definitions.len
-			g.stmt(it.decl)
-			fn_body := g.out.after(pos)
-			g.out.go_back(fn_body.len)
-			g.definitions.go_back(g.definitions.len - def_pos)
-			g.definitions.write(fn_body)
-			fsym := g.table.get_type_symbol(it.typ)
-			g.write('&${fsym.name}')
-		}
 		else {
 			// #printf("node=%d\n", node.typ);
 			println(term.red('cgen.expr(): bad node ' + typeof(node)))
@@ -1524,7 +1527,7 @@ fn (mut g Gen) assign_expr(node ast.AssignExpr) {
 		g.or_block(tmp_opt, or_stmts, return_type)
 		unwrapped_type_str := g.typ(return_type.set_flag(.unset))
 		ident := node.left as ast.Ident
-		if ident.info is ast.IdentVar {
+		if ident.kind != .blank_ident && ident.info is ast.IdentVar {
 			ident_var := ident.info as ast.IdentVar
 			if ident_var.is_optional {
 				// var is already an optional, just copy the value
@@ -1847,6 +1850,26 @@ fn (mut g Gen) ident(node ast.Ident) {
 	g.write(g.get_ternary_name(name))
 }
 
+fn (mut g Gen) concat_expr(node ast.ConcatExpr) {
+	styp := g.typ(node.return_type)
+	sym := g.table.get_type_symbol(node.return_type)
+	is_multi := sym.kind == .multi_return
+
+	if !is_multi {
+		g.expr(node.vals[0])
+	} else {
+		g.write('($styp){')
+		for i, expr in node.vals {
+			g.write('.arg$i=')
+			g.expr(expr)
+			if i < node.vals.len - 1 {
+				g.write(',')
+			}
+		}
+		g.write('}')
+	}
+}
+
 fn (mut g Gen) if_expr(node ast.IfExpr) {
 	if node.is_expr || g.inside_ternary != 0 {
 		g.inside_ternary++
diff --git a/vlib/v/parser/assign.v b/vlib/v/parser/assign.v
index fb4c77d3b8..cba046420f 100644
--- a/vlib/v/parser/assign.v
+++ b/vlib/v/parser/assign.v
@@ -6,13 +6,21 @@ module parser
 import v.ast
 
 fn (mut p Parser) assign_stmt() ast.Stmt {
-	is_static := p.tok.kind == .key_static
-	if is_static {
-		p.next()
+	return p.partial_assign_stmt([])
+}
+
+fn (mut p Parser) partial_assign_stmt(known_lhs []ast.Ident) ast.Stmt {
+	mut idents := known_lhs
+	mut op := p.tok.kind
+	// read (more) idents until assignment sign
+	for op !in [.decl_assign, .assign] {
+		idents << p.parse_assign_ident()
+		if p.tok.kind == .comma {
+			p.next()
+		}
+		op = p.tok.kind
 	}
-	idents := p.parse_assign_lhs()
-	op := p.tok.kind
-	p.next() // :=, =
+	p.next()
 	pos := p.tok.position()
 	exprs := p.parse_assign_rhs()
 	is_decl := op == .decl_assign
@@ -46,7 +54,7 @@ fn (mut p Parser) assign_stmt() ast.Stmt {
 		right: exprs
 		op: op
 		pos: pos
-		is_static: is_static
+		is_static: false // individual idents may be static
 	}
 }
 
@@ -72,31 +80,9 @@ pub fn (mut p Parser) assign_expr(left ast.Expr) ast.AssignExpr {
 	return node
 }
 
-fn (mut p Parser) parse_assign_lhs() []ast.Ident {
-	mut idents := []ast.Ident{}
-	for {
-		is_mut := p.tok.kind == .key_mut
-		if is_mut {
-			p.next()
-		}
-		is_static := p.tok.kind == .key_static
-		if is_static {
-			p.next()
-		}
-		mut ident := p.parse_ident(false, false)
-		ident.is_mut = is_mut
-		ident.info = ast.IdentVar{
-			is_mut: is_mut
-			is_static: is_static
-		}
-		idents << ident
-		if p.tok.kind == .comma {
-			p.next()
-		} else {
-			break
-		}
-	}
-	return idents
+fn (mut p Parser) parse_assign_ident() ast.Ident {
+	/// returns a single parsed ident
+	return p.parse_ident(false, false)
 }
 
 // right hand side of `=` or `:=` in `a,b,c := 1,2,3`
diff --git a/vlib/v/parser/parser.v b/vlib/v/parser/parser.v
index 1cceb0ca13..e62a64f1c7 100644
--- a/vlib/v/parser/parser.v
+++ b/vlib/v/parser/parser.v
@@ -447,9 +447,12 @@ pub fn (mut p Parser) stmt() ast.Stmt {
 			return p.for_stmt()
 		}
 		.name {
-			if p.peek_tok.kind in [.decl_assign, .comma] {
+			if p.peek_tok.kind == .decl_assign {
 				// `x := ...`
 				return p.assign_stmt()
+			} else if p.peek_tok.kind == .comma {
+				// `a, b ...`
+				return p.parse_comma_separated()
 			} else if p.peek_tok.kind == .colon {
 				// `label:`
 				name := p.check_name()
@@ -524,15 +527,11 @@ pub fn (mut p Parser) stmt() ast.Stmt {
 				name: name
 			}
 		}
+		.key_const {
+			p.error_with_pos('const can only be defined at the top level (outside of functions)', p.tok.position())
+		}
 		else {
-			if p.tok.kind == .key_const {
-				p.error_with_pos('const can only be defined at the top level (outside of functions)', p.tok.position())
-			}
-			epos := p.tok.position()
-			return ast.ExprStmt{
-				expr: p.expr(0)
-				pos: epos
-			}
+			return p.parse_comma_separated()
 		}
 	}
 }
@@ -645,27 +644,93 @@ pub fn (mut p Parser) warn_with_pos(s string, pos token.Position) {
 	}
 }
 
-pub fn (mut p Parser) parse_ident(is_c, is_js bool) ast.Ident {
-	// p.warn('name ')
-	pos := p.tok.position()
-	mut name := p.check_name()
-	if name == '_' {
-		return ast.Ident{
-			name: '_'
-			kind: .blank_ident
-			pos: pos
+fn (mut p Parser) parse_comma_separated() ast.Stmt {
+	// in here might be 1) multi-expr 2) multi-assign
+	// 1, a, c ... }       // multi-expression
+	// a, mut b ... :=/=   // multi-assign
+	// collect things upto hard boundaries
+	mut collected := []ast.Expr{}
+	mut op := p.tok.kind
+	for op !in [.rcbr, .decl_assign, .assign] {
+		if op == .name {
+			collected << p.name_expr()
+		} else {
+			collected << p.expr(0)
+		}
+		if p.tok.kind == .comma {
+			p.next()
+		} else {
+			break
+		}
+		op = p.tok.kind
+	}
+	is_assignment := p.tok.kind in [.decl_assign, .assign]
+	if is_assignment {
+		mut idents := []ast.Ident{}
+		for c in collected {
+			idents << c as ast.Ident
+		}
+		return p.partial_assign_stmt(idents)
+	} else {
+		if collected.len == 1 {
+			epos := p.tok.position()
+			return ast.ExprStmt{
+				expr: collected[0]
+				pos: epos
+			}
+		}
+		return ast.ExprStmt{
+			expr: ast.ConcatExpr {
+				vals: collected
+			}
+			pos: p.tok.position()
 		}
 	}
-	if p.expr_mod.len > 0 {
-		name = '${p.expr_mod}.$name'
+}
+
+pub fn (mut p Parser) parse_ident(is_c, is_js bool) ast.Ident {
+	// p.warn('name ')
+	is_mut := p.tok.kind == .key_mut
+	if is_mut {
+		p.next()
 	}
-	return ast.Ident{
-		kind: .unresolved
-		name: name
-		is_c: is_c
-		is_js: is_js
-		mod: p.mod
-		pos: pos
+	is_static := p.tok.kind == .key_static
+	if is_static {
+		p.next()
+	}
+	if p.tok.kind == .name {
+		pos := p.tok.position()
+		mut name := p.check_name()
+		if name == '_' {
+			return ast.Ident{
+				name: '_'
+				kind: .blank_ident
+				pos: pos
+				info: ast.IdentVar {
+					is_mut: false
+					is_static: false
+				}
+			}
+		}
+		if p.expr_mod.len > 0 {
+			name = '${p.expr_mod}.$name'
+		}
+		mut ident := ast.Ident{
+			kind: .unresolved
+			name: name
+			is_c: is_c
+			is_js: is_js
+			mod: p.mod
+			pos: pos
+		}
+		ident.is_mut = is_mut
+		ident.info = ast.IdentVar{
+			is_mut: is_mut
+			is_static: is_static
+		}
+		return ident
+	} else {
+		p.error('unexpected token `$p.tok.lit`')
 	}
 }
 
diff --git a/vlib/v/parser/pratt.v b/vlib/v/parser/pratt.v
index 4001c093c9..e5ac6739cd 100644
--- a/vlib/v/parser/pratt.v
+++ b/vlib/v/parser/pratt.v
@@ -15,6 +15,9 @@ pub fn (mut p Parser) expr(precedence int) ast.Expr {
 	p.is_stmt_ident = false
 	// Prefix
 	match p.tok.kind {
+		.key_mut, .key_static {
+			node = p.parse_assign_ident()
+		}
 		.name {
 			node = p.name_expr()
 			p.is_stmt_ident = is_stmt_ident
diff --git a/vlib/v/tests/complex_assign_test.v b/vlib/v/tests/complex_assign_test.v
index c675960d02..2d2c1ad0c1 100644
--- a/vlib/v/tests/complex_assign_test.v
+++ b/vlib/v/tests/complex_assign_test.v
@@ -1,3 +1,7 @@
+struct Object {
+	name string
+	value int
+}
 
 fn multireturner(n int, s string) (int, string) {
 	return n + 1, s
@@ -47,12 +51,55 @@ fn test_assign_multireturn_expression() {
 	assert i == 1
 	assert j == 'good'
 
-	// TODO: returning non-function calls does not work yet due to parsing issues
-	/*
-	e, f := if true {
-		1, 'awesome'
+	k, l, m := if true {
+		1, 'awesome', [13]
 	} else {
-		0, 'bad'
+		0, 'bad', [0]
 	}
-	*/
+	assert k == 1
+	assert l == 'awesome'
+	assert m == [13]
+
+	n, o, p := if false {
+		1, 'awesome', [13]
+	} else {
+		0, 'bad', [0]
+	}
+	assert n == 0
+	assert o == 'bad'
+	assert p == [0]
+
+	mut var1 := 17
+	var2 := 'awesome'
+	q, r, s := if true {
+		1 + var1, var2, [13]
+	} else {
+		0, 'bad', [0]
+	}
+	assert q == 18
+	assert r == 'awesome'
+	assert s == [13]
+
+	val1 := 1
+	val2 := 0
+	t, u, v := if true {
+		val1, 'awesome', [13]
+	} else {
+		val2, 'bad', [0]
+	}
+	assert t == val1
+	assert u == 'awesome'
+	assert v == [13]
+
+	val3 := Object { name: 'foo', value: 19 }
+	x, y, z := if true {
+		1 + 1, 'awe' + 'some', { val3 | name: 'bar' }
+	} else {
+		0, '0', Object {}
+	}
+	assert x == 2
+	assert y == 'awesome'
+	assert z.name == 'bar'
+	assert z.value == 19
+
 }