v.eval: add tests and fix runtime cast crash (#13019)

cmd/v/help/build.txt

@@ -37,6 +37,7 @@ NB: the build flags are shared with the run command too:
       Specify the backend to use while building the executable.
       Current list of supported backends:
       * `c` (default)       - V outputs C source code which is passed to a C compiler to be compiled.
+      * `interpret`         - Same as `v interpret` to run the V program
       * `js`                - V outputs JS source code which can be passed to NodeJS to be ran.
       * `js_browser`        - V outputs JS source code ready for the browser.
       * `js_node`           - V outputs JS source code to run with nodejs.

vlib/v/builder/compile.v

@@ -102,6 +102,10 @@ fn (b &Builder) exit_on_invalid_syntax() {
 }
 
 fn (mut b Builder) run_compiled_executable_and_exit() {
+	if b.pref.backend == .interpret {
+		// the interpreted code has already ran
+		return
+	}
 	if b.pref.skip_running {
 		return
 	}

vlib/v/builder/interpreterbuilder/v_interpret_test.v

@@ -0,0 +1,55 @@
+import os
+import rand
+import term
+
+const vexe = @VEXE
+
+fn interpreter_wrap(a string) string {
+	return 'fn main() {$a}'
+}
+
+fn interp_test(expression string, expected string) ? {
+	tmpdir := os.join_path(os.temp_dir(), 'v_interpret_test_$rand.ulid()')
+	os.mkdir_all(tmpdir) or {}
+	defer {
+		os.rmdir_all(tmpdir) or {}
+	}
+	//
+	tmpfile := os.join_path(tmpdir, 'input.v')
+	outfile := os.join_path(tmpdir, 'output.txt')
+	os.write_file(tmpfile, interpreter_wrap(expression)) ?
+	if os.system('"$vexe" interpret $tmpfile > $outfile') != 0 {
+		eprintln('>>> Failed to interpret V expression: |$expression|')
+		return error('v interp')
+	}
+	res := os.read_file(outfile) ?
+	output := res.trim_space()
+	if output != expected {
+		eprintln('>>> The output of the V expression, is not the same as the expected one')
+		eprintln(' V expression: $expression')
+		eprintln('       output: |$output|')
+		eprintln('     expected: |$expected|')
+		return error('test')
+	}
+	println('${term.colorize(term.green, 'OK')} ${term.colorize(term.bright_blue, expression.replace('\n',
+		' '))}')
+	println('   >> ${term.colorize(term.bright_yellow, output)}')
+}
+
+struct InterpTest {
+	input  string
+	output string
+}
+
+fn test_interpreter() ? {
+	mut tests := []InterpTest{}
+	tests << InterpTest{'println(3+3)', '6'}
+	tests << InterpTest{'println(3)', '3'}
+	tests << InterpTest{'println(3-4)', '-1'}
+	tests << InterpTest{'println(3*3)', '9'}
+	tests << InterpTest{'a := 3\nprintln(a*3)', '9'}
+	for test in tests {
+		interp_test(test.input, test.output) ?
+		assert true
+	}
+}

vlib/v/eval/eval.v

@@ -171,19 +171,26 @@ pub fn (mut e Eval) register_symbol(stmt ast.Stmt, mod string, file string) {
 					for i, branch in x.branches {
 						mut do_if := false
 						println('branch:$branch')
-						match (branch.cond as ast.Ident).name {
-							'windows' {
-								do_if = e.pref.os == .windows
+						match branch.cond {
+							ast.Ident {
+								match (branch.cond as ast.Ident).name {
+									'windows' {
+										do_if = e.pref.os == .windows
+									}
+									else {
+										e.error('unknown compile time if')
+									}
+								}
+								do_if = do_if || x.branches.len == i + 1
+								if do_if {
+									e.register_symbol_stmts(branch.stmts, mod, file)
+									break
+								}
 							}
 							else {
-								e.error('unknown compile time if')
+								eprintln('unsupported expression')
 							}
 						}
-						do_if = do_if || x.branches.len == i + 1
-						if do_if {
-							e.register_symbol_stmts(branch.stmts, mod, file)
-							break
-						}
 					}
 				}
 				else {

vlib/v/parser/v_parser_test.v

@@ -133,7 +133,7 @@ fn test_parse_expr() {
 	mut e := []ast.Stmt{}
 	table := ast.new_table()
 	vpref := &pref.Preferences{}
-	mut checker := checker.new_checker(table, vpref)
+	mut chk := checker.new_checker(table, vpref)
 	scope := &ast.Scope{
 		start_pos: 0
 		parent: 0
@@ -147,7 +147,7 @@ fn test_parse_expr() {
 		scope: scope
 		global_scope: scope
 	}
-	checker.check(program)
+	chk.check(program)
 	res := c.gen([program], table, vpref).after('#endif')
 	println('========')
 	println(res)