cgen: fix nested fn call with result/option propagation (#17738)

vlib/v/gen/c/cgen.v

@@ -136,6 +136,7 @@ mut:
 	inside_struct_init        bool
 	inside_or_block           bool
 	inside_call               bool
+	inside_curry_call         bool // inside foo()()!, foo()()?, foo()()
 	inside_for_c_stmt         bool
 	inside_comptime_for_field bool
 	inside_cast_in_heap       int // inside cast to interface type in heap (resolve recursive calls)
@@ -144,6 +145,7 @@ mut:
 	inside_lambda             bool
 	inside_for_in_any_cond    bool
 	inside_cinit              bool
+	last_tmp_call_var         []string
 	loop_depth                int
 	ternary_names             map[string]string
 	ternary_level_names       map[string][]string

vlib/v/gen/c/fn.v

@@ -677,8 +677,29 @@ fn (mut g Gen) call_expr(node ast.CallExpr) {
 		g.is_fn_index_call = true
 		g.expr(node.left)
 		g.is_fn_index_call = false
-	} else if node.left is ast.CallExpr && node.name == '' {
-		g.expr(node.left)
+	} else if !g.inside_curry_call && node.left is ast.CallExpr && node.name == '' {
+		if node.or_block.kind == .absent {
+			g.expr(node.left)
+		} else {
+			old_inside_curry_call := g.inside_curry_call
+			g.inside_curry_call = true
+			ret_typ := node.return_type
+
+			line := g.go_before_stmt(0)
+			g.empty_line = true
+
+			tmp_res := g.new_tmp_var()
+			g.write('${g.typ(ret_typ)} ${tmp_res} = ')
+
+			g.last_tmp_call_var << tmp_res
+			g.expr(node.left)
+			g.expr(node)
+
+			g.inside_curry_call = old_inside_curry_call
+			g.write(line)
+			g.write('*(${g.base_type(ret_typ)}*)${tmp_res}.data')
+			return
+		}
 	}
 	old_inside_call := g.inside_call
 	g.inside_call = true
@@ -689,7 +710,7 @@ fn (mut g Gen) call_expr(node ast.CallExpr) {
 		&& g.pref.gc_mode in [.boehm_full, .boehm_incr, .boehm_full_opt, .boehm_incr_opt]
 	gen_or := node.or_block.kind != .absent // && !g.is_autofree
 	is_gen_or_and_assign_rhs := gen_or && !g.discard_or_result
-	mut cur_line := if is_gen_or_and_assign_rhs || gen_keep_alive { // && !g.is_autofree {
+	mut cur_line := if !g.inside_curry_call && (is_gen_or_and_assign_rhs || gen_keep_alive) { // && !g.is_autofree {
 		// `x := foo() or { ...}`
 		// cut everything that has been generated to prepend option variable creation
 		line := g.go_before_stmt(0)
@@ -699,7 +720,15 @@ fn (mut g Gen) call_expr(node ast.CallExpr) {
 		''
 	}
 	// g.write('/*EE line="$cur_line"*/')
-	tmp_opt := if gen_or || gen_keep_alive { g.new_tmp_var() } else { '' }
+	tmp_opt := if gen_or || gen_keep_alive {
+		if g.inside_curry_call && g.last_tmp_call_var.len > 0 {
+			g.last_tmp_call_var.pop()
+		} else {
+			g.new_tmp_var()
+		}
+	} else {
+		''
+	}
 	if gen_or || gen_keep_alive {
 		mut ret_typ := node.return_type
 		if g.table.sym(ret_typ).kind == .alias {
@@ -717,7 +746,7 @@ fn (mut g Gen) call_expr(node ast.CallExpr) {
 			g.writeln('if (${g.infix_left_var_name}) {')
 			g.indent++
 			g.write('${tmp_opt} = ')
-		} else {
+		} else if !g.inside_curry_call {
 			g.write('${styp} ${tmp_opt} = ')
 			if node.left is ast.AnonFn {
 				g.expr(node.left)
@@ -752,7 +781,7 @@ fn (mut g Gen) call_expr(node ast.CallExpr) {
 		}
 		if unwrapped_typ == ast.void_type {
 			g.write('\n ${cur_line}')
-		} else {
+		} else if !g.inside_curry_call {
 			if !g.inside_const_opt_or_res {
 				g.write('\n ${cur_line} (*(${unwrapped_styp}*)${tmp_opt}.data)')
 			} else {

vlib/v/parser/parser.v

@@ -2633,11 +2633,29 @@ pub fn (mut p Parser) name_expr() ast.Expr {
 				pos := p.tok.pos()
 				args := p.call_args()
 				p.check(.rpar)
+
+				mut or_kind := ast.OrKind.absent
+				mut or_stmts := []ast.Stmt{}
+				mut or_pos := p.tok.pos()
+				if p.tok.kind in [.not, .question] {
+					or_kind = if p.tok.kind == .not { .propagate_result } else { .propagate_option }
+					p.next()
+				}
+				if p.tok.kind == .key_orelse {
+					// `foo() or {}``
+					or_kind = .block
+					or_stmts, or_pos = p.or_block(.with_err_var)
+				}
 				node = ast.CallExpr{
 					left: node
 					args: args
 					pos: pos
 					scope: p.scope
+					or_block: ast.OrExpr{
+						stmts: or_stmts
+						kind: or_kind
+						pos: or_pos
+					}
 				}
 			}
 		}

vlib/v/tests/call_on_anon_test.v

@@ -0,0 +1,55 @@
+fn f1(s string) fn (string) !string {
+	return fn [s] (str string) !string {
+		return s + str
+	}
+}
+
+fn f2(s string) fn (string) ?string {
+	return fn [s] (str string) ?string {
+		return s + str
+	}
+}
+
+fn f3(s string) fn (string) string {
+	return fn [s] (str string) string {
+		return s + str
+	}
+}
+
+fn f4(s string) fn (string) ?string {
+	return fn (str string) ?string {
+		return none
+	}
+}
+
+fn f5(s string) fn (string) !string {
+	return fn (str string) !string {
+		return error('test')
+	}
+}
+
+fn test_call_nested_anon() {
+	println(main.f1('V')('Lang')!)
+	s1 := main.f1('V')('Lang')!
+	println(s1)
+	s2 := main.f1('V')('Lang') or { 'ErrLang' }
+	println(s2)
+	s3 := main.f2('V')('Lang')?
+	println(s3)
+	s4 := main.f2('V')('Lang') or { 'NoneLang' }
+	println(s4)
+	s := main.f3('V')('Lang')
+	println(s)
+	assert s == 'VLang'
+	assert s1 == 'VLang'
+	assert s2 == 'VLang'
+	assert s3 == 'VLang'
+	assert s4 == 'VLang'
+
+	s5 := main.f4('V')('Lang') or { 'Lang++' }
+	println(s5)
+	assert s5 == 'Lang++'
+	s6 := main.f5('V')('Lang') or { '${err}' }
+	println(s6)
+	assert s6 == 'test'
+}