fix(checker): set correct return type of array.last()

CHANGELOG.md

@@ -15,6 +15,7 @@ _unreleased_
 
 ### Type Checks
 - Ensure function parameter type exists
+- Properly check return type of `array.last()`
 
 ### C Backend
 - builder: Fixes for using the C backend on windows

lib/bait/checker/fun.bt

@@ -270,6 +270,11 @@ fun (mut c Checker) method_call(mut node ast.CallExpr) ast.Type {
 		return left_expr_type
 	}
 
+	// Array methods with return type `any`
+	if left_sym.kind == .array and ['last'].contains(node.name) {
+		return (left_sym.info as ast.ArrayInfo).elem_type
+	}
+
 	if node.concrete_types.length > 0 {
 		def.concrete_types.push(node.concrete_types)
 

tests/out/error/array/magic_methods.in.bt

@@ -1,5 +1,9 @@
-	mut a := [1, 2, 3]
-	a.push(true)
-	a.index('a')
-	a.contains(12 as i16)
-	a.concat(['b', 'c'])
+mut a := [1, 2, 3]
+
+a.push(true)
+a.index('a') // FIXME should raise error
+a.contains(12 as i16)
+a.concat(['b', 'c'])
+
+mut x := 'a'
+x = a.last()

tests/out/error/array/magic_methods.out

@@ -1,4 +1,4 @@
-tests/out/error/array/magic_methods.in.bt:2:7 error: type bool not matches i32 in argument 1
-tests/out/error/array/magic_methods.in.bt:3:8 error: type string not matches i32 in argument 1
-tests/out/error/array/magic_methods.in.bt:4:11 error: type i16 not matches i32 in argument 1
-tests/out/error/array/magic_methods.in.bt:5:9 error: type []string not matches []i32 in argument 1
+tests/out/error/array/magic_methods.in.bt:3:6 error: type bool not matches i32 in argument 1
+tests/out/error/array/magic_methods.in.bt:5:10 error: type i16 not matches i32 in argument 1
+tests/out/error/array/magic_methods.in.bt:6:8 error: type []string not matches []i32 in argument 1
+tests/out/error/array/magic_methods.in.bt:9:2 error: cannot assign type i32 to string

tests/output_test.bt

@@ -4,10 +4,7 @@
 import os
 import bait.util.testing
 
-const ERR_SKIP := [
-	// Known fail due to regression
-	'tests/out/error/array/magic_methods.in.bt',
-]
+const ERR_SKIP := []
 
 const DIR := os.dir($FILE)
 const ENABLE_FIX := os.ARGS.contains('--fix')