builder: fix detecting duplicate functions (#9033)

vlib/v/builder/builder.v

@@ -366,7 +366,7 @@ fn (b &Builder) print_warnings_and_errors() {
 					}
 				}
 			}
-			if redefine_conflicts.len > 1 {
+			if redefines.len > 0 {
 				eprintln('redefinition of function `$fn_name`')
 				for redefine in redefines {
 					eprintln(util.formatted_error('conflicting declaration:', redefine.fheader,

vlib/v/checker/tests/fn_duplicate.out

@@ -0,0 +1,13 @@
+redefinition of function `main.f`
+vlib/v/checker/tests/fn_duplicate.vv:1:1: conflicting declaration: fn f()
+    1 | fn f() {
+      | ~~~~~~
+    2 |     
+    3 | }
+vlib/v/checker/tests/fn_duplicate.vv:5:1: conflicting declaration: fn f(i int)
+    3 | }
+    4 | 
+    5 | fn f(i int) {
+      | ~~~~~~~~~~~
+    6 |     
+    7 | }

vlib/v/checker/tests/fn_duplicate.vv

@@ -0,0 +1,7 @@
+fn f() {
+	
+}
+
+fn f(i int) {
+	
+}

vlib/v/parser/fn.v

@@ -329,8 +329,8 @@ fn (mut p Parser) fn_decl() ast.FnDecl {
 		} else {
 			name = p.prepend_mod(name)
 		}
-		if _ := p.table.find_fn(name) {
-			p.fn_redefinition_error(name)
+		if !p.pref.translated && language == .v && name in p.table.fns {
+			p.table.redefined_fns << name
 		}
 		// p.warn('reg functn $name ()')
 		p.table.register_fn(table.Fn{
@@ -809,21 +809,6 @@ fn (mut p Parser) check_fn_atomic_arguments(typ table.Type, pos token.Position)
 	}
 }
 
-fn (mut p Parser) fn_redefinition_error(name string) {
-	if p.pref.translated {
-		return
-	}
-	// Find where this function was already declared
-	// TODO
-	/*
-	for file in p.ast_files {
-
-	}
-	*/
-	p.table.redefined_fns << name
-	// p.error('redefinition of function `$name`')
-}
-
 fn have_fn_main(stmts []ast.Stmt) bool {
 	for stmt in stmts {
 		if stmt is ast.FnDecl {