cgen: show more informative errors, instead of a `invalid type (typ=0 idx=0)` verror panic

vlib/v/ast/ast.v

@@ -318,6 +318,7 @@ pub:
 pub mut:
 	typ             table.Type
 	is_tmp_autofree bool
+	pos             token.Position
 	// tmp_name        string // for autofree
 }
 

vlib/v/checker/checker.v

@@ -1057,6 +1057,10 @@ pub fn (mut c Checker) call_method(mut call_expr ast.CallExpr) table.Type {
 	left_type := c.expr(call_expr.left)
 	is_generic := left_type.has_flag(.generic)
 	call_expr.left_type = left_type
+	// Set default values for .return_type & .receiver_type too,
+	// or there will be hard to diagnose 0 type panics in cgen.
+	call_expr.return_type = left_type
+	call_expr.receiver_type = left_type
 	left_type_sym := c.table.get_type_symbol(c.unwrap_generic(left_type))
 	method_name := call_expr.name
 	mut unknown_method_msg := 'unknown method: `${left_type_sym.source_name}.$method_name`'
@@ -1095,8 +1099,6 @@ pub fn (mut c Checker) call_method(mut call_expr ast.CallExpr) table.Type {
 		for arg in call_expr.args {
 			arg_type = c.expr(arg.expr)
 		}
-		call_expr.return_type = left_type
-		call_expr.receiver_type = left_type
 		if method_name == 'map' {
 			// check fn
 			c.check_map_and_filter(true, elem_typ, call_expr)

vlib/v/gen/cgen.v

@@ -2309,6 +2309,9 @@ fn (mut g Gen) expr(node ast.Expr) {
 				g.typeof_name(left)
 				return
 			}
+			if node.expr_type == 0 {
+				g.checker_bug('unexpected SelectorExpr.expr_type = 0', node.pos)
+			}
 			sym := g.table.get_type_symbol(node.expr_type)
 			if sym.kind == .array_fixed {
 				assert node.field_name == 'len'
@@ -3886,7 +3889,11 @@ fn (mut g Gen) struct_init(struct_init ast.StructInit) {
 	for i, field in struct_init.fields {
 		inited_fields[field.name] = i
 		if sym.info is table.Struct as struct_info {
-			tfield := struct_info.fields.filter(it.name == field.name)[0]
+			equal_fields := struct_info.fields.filter(it.name == field.name)
+			if equal_fields.len == 0 {
+				continue
+			}
+			tfield := equal_fields[0]
 			if tfield.embed_alias_for.len != 0 {
 				continue
 			}
@@ -3894,6 +3901,9 @@ fn (mut g Gen) struct_init(struct_init ast.StructInit) {
 		if sym.kind != .struct_ {
 			field_name := c_name(field.name)
 			g.write('.$field_name = ')
+			if field.typ == 0 {
+				g.checker_bug('struct init, field.typ is 0', field.pos)
+			}
 			field_type_sym := g.table.get_type_symbol(field.typ)
 			mut cloned := false
 			if g.autofree && !field.typ.is_ptr() && field_type_sym.kind in [.array, .string] {
@@ -3931,7 +3941,11 @@ fn (mut g Gen) struct_init(struct_init ast.StructInit) {
 		// nr_fields = info.fields.len
 		for field in info.fields {
 			if sym.info is table.Struct as struct_info {
-				tfield := struct_info.fields.filter(it.name == field.name)[0]
+				equal_fields := struct_info.fields.filter(it.name == field.name)
+				if equal_fields.len == 0 {
+					continue
+				}
+				tfield := equal_fields[0]
 				if tfield.embed_alias_for.len != 0 {
 					continue
 				}
@@ -4132,8 +4146,13 @@ fn verror(s string) {
 }
 
 fn (g &Gen) error(s string, pos token.Position) {
-	p := if pos.line_nr == 0 { '?' } else { '${pos.line_nr + 1}' }
+	ferror := util.formatted_error('cgen error:', s, g.file.path, pos)
-	util.verror('$g.file.path:$p: cgen error', s)
+	eprintln(ferror)
+	exit(1)
+}
+
+fn (g &Gen) checker_bug(s string, pos token.Position) {
+	g.error('checker bug; $s', pos)
 }
 
 fn (mut g Gen) write_init_function() {

vlib/v/gen/fn.v

@@ -326,7 +326,10 @@ pub fn (g &Gen) unwrap_generic(typ table.Type) table.Type {
 fn (mut g Gen) method_call(node ast.CallExpr) {
 	// TODO: there are still due to unchecked exprs (opt/some fn arg)
 	if node.left_type == 0 {
-		verror('method receiver type is 0, this means there are some uchecked exprs')
+		g.checker_bug('CallExpr.left_type is 0 in method_call', node.pos)
+	}
+	if node.receiver_type == 0 {
+		g.checker_bug('CallExpr.receiver_type is 0 in method_call', node.pos)
 	}
 	// mut receiver_type_name := g.cc_type(node.receiver_type)
 	// mut receiver_type_name := g.typ(node.receiver_type)
@@ -545,6 +548,9 @@ fn (mut g Gen) fn_call(node ast.CallExpr) {
 	// Handle `print(x)`
 	if is_print && node.args[0].typ != table.string_type { // && !free_tmp_arg_vars {
 		typ := node.args[0].typ
+		if typ == 0 {
+			g.checker_bug('print arg.typ is 0', node.pos)
+		}
 		mut styp := g.typ(typ)
 		sym := g.table.get_type_symbol(typ)
 		if typ.is_ptr() {
@@ -831,6 +837,9 @@ fn (mut g Gen) call_args(node ast.CallExpr) {
 fn (mut g Gen) ref_or_deref_arg(arg ast.CallArg, expected_type table.Type) {
 	arg_is_ptr := expected_type.is_ptr() || expected_type.idx() in table.pointer_type_idxs
 	expr_is_ptr := arg.typ.is_ptr() || arg.typ.idx() in table.pointer_type_idxs
+	if expected_type == 0 {
+		g.checker_bug('ref_or_deref_arg expected_type is 0', arg.pos)
+	}
 	exp_sym := g.table.get_type_symbol(expected_type)
 	if arg.is_mut && !arg_is_ptr {
 		g.write('&/*mut*/')
@@ -851,6 +860,9 @@ fn (mut g Gen) ref_or_deref_arg(arg ast.CallArg, expected_type table.Type) {
 			}
 		}
 		if !g.is_json_fn {
+			if arg.typ == 0 {
+				g.checker_bug('ref_or_deref_arg arg.typ is 0', arg.pos)
+			}
 			arg_typ_sym := g.table.get_type_symbol(arg.typ)
 			expected_deref_type := if expected_type.is_ptr() { expected_type.deref() } else { expected_type }
 			is_sum_type := g.table.get_type_symbol(expected_deref_type).kind == .sum_type

vlib/v/parser/fn.v

@@ -140,6 +140,7 @@ pub fn (mut p Parser) call_args() []ast.CallArg {
 			share: table.sharetype_from_flags(is_shared, is_atomic)
 			expr: e
 			comments: comments
+			pos: p.tok.position()
 		}
 		if p.tok.kind != .rpar {
 			p.check(.comma)