From fe8a6abb41c1f4c09694ffb1f5487a8879c0e60e Mon Sep 17 00:00:00 2001
From: joe-conigliaro <joe-conigliaro@users.noreply.github.com>
Date: Thu, 26 Dec 2019 13:40:18 +1100
Subject: [PATCH] compiler2: update operator precedence and associativity
 (#3218)

---
 vlib/compiler2/ast/ast.v            | 56 +++++++++++++++--------------
 vlib/compiler2/parser/parser_test.v |  5 ++-
 vlib/compiler2/token/token.v        | 37 +++++++++++++++----
 3 files changed, 64 insertions(+), 34 deletions(-)

diff --git a/vlib/compiler2/ast/ast.v b/vlib/compiler2/ast/ast.v
index 9deab68fcb..2201d7ba9a 100644
--- a/vlib/compiler2/ast/ast.v
+++ b/vlib/compiler2/ast/ast.v
@@ -13,10 +13,12 @@ struct Foo {}
 // pub type Expr = Foo | IfExpr | BinaryExpr | IntegerExpr
 pub type Expr = Foo | IfExpr | BinaryExpr | ScalarExpr | UnaryExpr
 
-// pub struct IntegerExpr {
-// pub:
-// 	val int
-// }
+/*
+pub struct IntegerExpr {
+pub:
+	val int
+}
+*/
 
 /*
 pub enum Expr {
@@ -92,28 +94,30 @@ pub fn (x Expr) str() string {
 	}
 }
 
-// enum BinaryOp {
-// 	sum
-// 	difference
-// 	product
-// 	quotient
-// 	remainder
-// 	bitwise_and
-// 	bitwise_or
-// 	bitwise_xor
-// 	left_shift
-// 	right_shift
+/*
+enum BinaryOp {
+	sum
+	difference
+	product
+	quotient
+	remainder
+	bitwise_and
+	bitwise_or
+	bitwise_xor
+	left_shift
+	right_shift
 
-// 	equality
-// 	inequality
-// 	less_than
-// 	less_than_or_equal
-// 	more_than
-// 	more_than_or_equal
+	equality
+	inequality
+	less_than
+	less_than_or_equal
+	more_than
+	more_than_or_equal
 
-// 	in_check
+	in_check
 
-// 	//These are suffixed with `bool` to prevent conflict with the keyword `or`
-// 	and_bool
-// 	or_bool
-// }
+	//These are suffixed with `bool` to prevent conflict with the keyword `or`
+	and_bool
+	or_bool
+}
+*/
diff --git a/vlib/compiler2/parser/parser_test.v b/vlib/compiler2/parser/parser_test.v
index 72d5d0ff57..3597ed6667 100644
--- a/vlib/compiler2/parser/parser_test.v
+++ b/vlib/compiler2/parser/parser_test.v
@@ -12,12 +12,15 @@ fn test_parser() {
 	println('\n')
 	
 	text_expr := [
+		'1 += 2',
+		'1.2 + 3.4',
 		'4 + 4',
 		'1 + 2 * 5',
 		'(2 * 3) / 2',
 		'3 + (7 * 6)',
 		'2 ^ 8 * (7 * 6)',
-		'(2) + (17*2-30) * (5)+2 - (8/2)*4'
+		'20 + (10 * 15) / 5', // 50
+		'(2) + (17*2-30) * (5)+2 - (8/2)*4' // 8
 	]
 	for s in text_expr {
 		// print using str method
diff --git a/vlib/compiler2/token/token.v b/vlib/compiler2/token/token.v
index 5946ad91f3..de5b538ce4 100644
--- a/vlib/compiler2/token/token.v
+++ b/vlib/compiler2/token/token.v
@@ -313,10 +313,16 @@ const (
 // Precedence returns a tokens precedence if defined, otherwise lowest_prec
 pub fn (tok Token) precedence() int {
 	match tok {
-		.plus, .minus { return 4 }
-		.mul, .div { return 4 }
-		.xor { return 6 }
-		.mod {return 7 }
+		// `*` |  `/` | `%` | `<<` | `>>` | `&`
+		.mul, .div, .left_shift, .righ_shift, .amp { return 7 }
+		// `+` |  `-` |  `|` | `^`
+		.plus, .minus, .pipe, .xor { return 6 }
+		// `==` | `!=` | `<` | `<=` | `>` | `>=`
+		.eq, .ne, .lt, .le, .gt, .ge { return 5 }
+		// `&&`
+		.and { return 4 }
+		// `||`
+		.logical_or { return 3 }
 		else { return lowest_prec }
 	}
 }
@@ -332,15 +338,25 @@ pub fn (tok Token) is_scalar() bool {
 // is_unary returns true if the token can be in a unary expression
 pub fn (tok Token) is_unary() bool {
 	match tok {
-		.plus, .minus { return true }
+		//  `+` | `-` | `!` | `~` | `*` | `&`
+		.plus, .minus, .not, .bit_not, .mul, .amp { return true }
 		else { return false }
 	}
 }
 
+// NOTE: do we need this for all tokens (is_left_assoc / is_right_assoc), 
+// or only ones with the same precedence? 
+
 // is_left_assoc returns true if the token is left associative
 pub fn (tok Token) is_left_assoc() bool {
 	match tok {
-		.number, .plus, .minus, .mul, .div, .mod { return true }
+		// .number,
+		// `*` | `/` | `%`
+		.mul, .div, .mod,
+		// `^` | `||` | `&`
+		.xor, .logical_or, .and,
+		// `,`
+		.comma { return true }
 		else { return false }
 	}
 }
@@ -348,7 +364,14 @@ pub fn (tok Token) is_left_assoc() bool {
 // is_right_assoc returns true if the token is right associative
 pub fn (tok Token) is_right_assoc() bool {
 	match tok {
-		.xor { return true }
+		// `+` | `-` | `!` | `++` | `--`
+		.plus, .minus, .not, .inc, .dec,
+		// `=` | `+=` | `-=` | `*=` | `/=` 
+		.assign, .plus_assign, .minus_assign, .mult_assign, .div_assign,
+		// `%=` | `>>=` | `<<=`
+		.mod_assign, .righ_shift_assign, .left_shift_assign,
+		// `&=` | `^=` | `|=`
+		.and_assign, .xor_assign, .or_assign { return true }
 		else { return false }
 	}
 }