ast, parser, cgen: fix generic struct init with inconsistent generic types (#17639)

vlib/v/ast/table.v

@@ -1714,6 +1714,7 @@ pub fn (mut t Table) resolve_generic_to_concrete(generic_type Type, generic_name
 		Struct, Interface, SumType {
 			if sym.info.is_generic {
 				mut nrt := '${sym.name}['
+				mut rnrt := '${sym.rname}['
 				mut t_generic_names := generic_names.clone()
 				mut t_concrete_types := concrete_types.clone()
 				if sym.generic_types.len > 0 && sym.generic_types.len == sym.info.generic_types.len
@@ -1744,17 +1745,23 @@ pub fn (mut t Table) resolve_generic_to_concrete(generic_type Type, generic_name
 					{
 						gts := t.sym(ct)
 						nrt += gts.name
+						rnrt += gts.name
 						if i != sym.info.generic_types.len - 1 {
 							nrt += ', '
+							rnrt += ', '
 						}
 					} else {
 						return none
 					}
 				}
 				nrt += ']'
+				rnrt += ']'
 				mut idx := t.type_idxs[nrt]
 				if idx == 0 {
-					idx = t.add_placeholder_type(nrt, .v)
+					idx = t.type_idxs[rnrt]
+					if idx == 0 {
+						idx = t.add_placeholder_type(nrt, .v)
+					}
 				}
 				return new_type(idx).derive_add_muls(generic_type).clear_flag(.generic)
 			}

vlib/v/ast/types.v

@@ -94,6 +94,7 @@ pub mut:
 	kind          Kind
 	name          string // the internal & source name of the type, i.e. `[5]int`.
 	cname         string // the name with no dots for use in the generated C code
+	rname         string // the raw name
 	methods       []Fn
 	generic_types []Type
 	mod           string

vlib/v/checker/check_types.v

@@ -983,7 +983,11 @@ fn (mut c Checker) infer_fn_generic_types(func ast.Fn, mut node ast.CallExpr) {
 					mut concrete_types := []ast.Type{}
 					match arg_sym.info {
 						ast.Struct, ast.Interface, ast.SumType {
-							generic_types = arg_sym.info.generic_types.clone()
+							if param_type_sym.generic_types.len > 0 {
+								generic_types = param_type_sym.generic_types.clone()
+							} else {
+								generic_types = arg_sym.info.generic_types.clone()
+							}
 							concrete_types = arg_sym.info.concrete_types.clone()
 						}
 						else {}

vlib/v/gen/c/cgen.v

@@ -1325,7 +1325,7 @@ fn (mut g Gen) cc_type(typ ast.Type, is_prefix_struct bool) string {
 	// TODO: this needs to be removed; cgen shouldn't resolve generic types (job of checker)
 	match sym.info {
 		ast.Struct, ast.Interface, ast.SumType {
-			if sym.info.is_generic {
+			if sym.info.is_generic && sym.generic_types.len == 0 {
 				mut sgtyps := '_T'
 				for gt in sym.info.generic_types {
 					gts := g.table.sym(g.unwrap_generic(gt))

vlib/v/parser/parse_type.v

@@ -682,6 +682,7 @@ pub fn (mut p Parser) find_type_or_add_placeholder(name string, language ast.Lan
 						idx = p.table.register_sym(ast.TypeSymbol{
 							...sym
 							name: sym_name
+							rname: sym.name
 							generic_types: p.struct_init_generic_types.clone()
 						})
 					}

vlib/v/tests/generics_struct_init_with_inconsistent_generic_types_7_test.v

@@ -0,0 +1,14 @@
+struct MyData[T] {
+}
+
+fn myfunc[U](a MyData[U]) string {
+	println(a)
+	return '${a}'
+}
+
+fn test_generics_struct_init_with_inconsistent_generic_types() {
+	d1 := MyData[int]{}
+	r1 := myfunc(d1)
+	println(r1)
+	assert r1 == 'MyData[int]{}'
+}