From 35a0fe79f99c2259c2a143019b5d4714df8e98ce Mon Sep 17 00:00:00 2001
From: Delyan Angelov <delian66@gmail.com>
Date: Wed, 25 Nov 2020 13:41:05 +0200
Subject: [PATCH] cgen: generate an unique sort comparator function for each
 .sort() call

---
 vlib/v/gen/cgen.v                             | 74 +++++++++----------
 .../sorting_by_different_criteria_test.v      | 23 ++++++
 2 files changed, 59 insertions(+), 38 deletions(-)
 create mode 100644 vlib/v/tests/sorting_by_different_criteria_test.v

diff --git a/vlib/v/gen/cgen.v b/vlib/v/gen/cgen.v
index 6494d3c717..79e180c695 100644
--- a/vlib/v/gen/cgen.v
+++ b/vlib/v/gen/cgen.v
@@ -4879,50 +4879,48 @@ fn (mut g Gen) gen_array_sort(node ast.CallExpr) {
 				verror('usage: .sort(a.field < b.field)')
 			}
 			// verror('sort(): unhandled type $typ $q.name')
-			compare_fn = 'compare_' + g.typ(typ)
+			tmp_name := g.new_tmp_var()
+			compare_fn = 'compare_${tmp_name}_' + g.typ(typ)
 			if is_reverse {
 				compare_fn += '_reverse'
 			}
-			if _ := g.table.find_fn(compare_fn) {
-			} else {
-				// Register a new custom `compare_xxx` function for qsort()
-				g.table.register_fn({
-					name: compare_fn
-					return_type: table.int_type
-				})
-				infix_expr := node.args[0].expr as ast.InfixExpr
-				styp := g.typ(typ)
-				// Variables `a` and `b` are used in the `.sort(a < b)` syntax, so we can reuse them
-				// when generating the function as long as the args are named the same.
-				g.definitions.writeln('int $compare_fn ($styp* a, $styp* b) {')
-				field_type := g.typ(infix_expr.left_type)
-				left_expr_str := g.write_expr_to_string(infix_expr.left).replace('.',
-					'->')
-				right_expr_str := g.write_expr_to_string(infix_expr.right).replace('.',
-					'->')
-				g.definitions.writeln('$field_type a_ = $left_expr_str;')
-				g.definitions.writeln('$field_type b_ = $right_expr_str;')
-				mut op1, mut op2 := '', ''
-				if infix_expr.left_type == table.string_type {
-					if is_reverse {
-						op1 = 'string_gt(a_, b_)'
-						op2 = 'string_lt(a_, b_)'
-					} else {
-						op1 = 'string_lt(a_, b_)'
-						op2 = 'string_gt(a_, b_)'
-					}
+			// Register a new custom `compare_xxx` function for qsort()
+			g.table.register_fn({
+				name: compare_fn
+				return_type: table.int_type
+			})
+			infix_expr := node.args[0].expr as ast.InfixExpr
+			styp := g.typ(typ)
+			// Variables `a` and `b` are used in the `.sort(a < b)` syntax, so we can reuse them
+			// when generating the function as long as the args are named the same.
+			g.definitions.writeln('int $compare_fn ($styp* a, $styp* b) {')
+			field_type := g.typ(infix_expr.left_type)
+			left_expr_str := g.write_expr_to_string(infix_expr.left).replace_once('.',
+				'->')
+			right_expr_str := g.write_expr_to_string(infix_expr.right).replace_once('.',
+				'->')
+			g.definitions.writeln('$field_type a_ = $left_expr_str;')
+			g.definitions.writeln('$field_type b_ = $right_expr_str;')
+			mut op1, mut op2 := '', ''
+			if infix_expr.left_type == table.string_type {
+				if is_reverse {
+					op1 = 'string_gt(a_, b_)'
+					op2 = 'string_lt(a_, b_)'
 				} else {
-					if is_reverse {
-						op1 = 'a_ > b_'
-						op2 = 'a_ < b_'
-					} else {
-						op1 = 'a_ < b_'
-						op2 = 'a_ > b_'
-					}
+					op1 = 'string_lt(a_, b_)'
+					op2 = 'string_gt(a_, b_)'
+				}
+			} else {
+				if is_reverse {
+					op1 = 'a_ > b_'
+					op2 = 'a_ < b_'
+				} else {
+					op1 = 'a_ < b_'
+					op2 = 'a_ > b_'
 				}
-				g.definitions.writeln('if ($op1) return -1;')
-				g.definitions.writeln('if ($op2) return 1; return 0; }\n')
 			}
+			g.definitions.writeln('if ($op1) return -1;')
+			g.definitions.writeln('if ($op2) return 1; return 0; }\n')
 		}
 	}
 	if is_reverse && !compare_fn.ends_with('_reverse') {
diff --git a/vlib/v/tests/sorting_by_different_criteria_test.v b/vlib/v/tests/sorting_by_different_criteria_test.v
new file mode 100644
index 0000000000..22dc6b1617
--- /dev/null
+++ b/vlib/v/tests/sorting_by_different_criteria_test.v
@@ -0,0 +1,23 @@
+struct Child {
+	f f64
+}
+
+struct Parent {
+	child Child
+	name  string
+}
+
+fn test_sorting_by_different_criteria_in_same_function() {
+	mut arr := [
+		Parent{Child{0.2}, 'def'},
+		Parent{Child{0.1}, 'xyz'},
+		Parent{Child{0.3}, 'abc'},
+	]
+	assert arr[0].name == 'def'
+	arr.sort(a.name < b.name)
+	// println(arr)
+	assert arr[0].name == 'abc'
+	// println(arr)
+	arr.sort(a.child.f < b.child.f)
+	assert arr[0].name == 'xyz'
+}