cgen: add a _T_ prefix in the C names for generic fn instances; fixes #6927 (#6999)

vlib/v/gen/fn.v

@@ -60,9 +60,10 @@ fn (mut g Gen) gen_fn_decl(it ast.FnDecl, skip bool) {
 	}
 	mut type_name := g.typ(it.return_type)
 	if g.cur_generic_type != 0 {
-		// foo<T>() => foo_int(), foo_string() etc
+		// foo<T>() => foo_T_int(), foo_T_string() etc
 		gen_name := g.typ(g.cur_generic_type)
-		name += '_' + gen_name
+		// Using _T_ to differentiate between get<string> and get_string
+		name += '_T_' + gen_name
 	}
 	// if g.pref.show_cc && it.is_builtin {
 	// println(name)
@@ -534,8 +535,9 @@ fn (mut g Gen) fn_call(node ast.CallExpr) {
 		name = c_name(name)
 	}
 	if node.generic_type != table.void_type && node.generic_type != 0 {
-		// `foo<int>()` => `foo_int()`
-		name += '_' + g.typ(node.generic_type)
+		// Using _T_ to differentiate between get<string> and get_string
+		// `foo<int>()` => `foo_T_int()`
+		name += '_T_' + g.typ(node.generic_type)
 	}
 	// TODO2
 	// cgen shouldn't modify ast nodes, this should be moved

vlib/v/tests/generic_functions_with_normal_function_test.v

@@ -0,0 +1,12 @@
+fn get<T>(typ T) T {
+   return typ
+}
+
+fn get_string(typ string) string {
+   return 'boom'
+}
+
+fn test_generic_with_same_type() {
+	assert get_string('') == 'boom'
+	assert get<string>('hello') == 'hello'
+}