main: add interp tests

This one needed more advanced checking of the error messages, because we
don't want to hardcode things like `!dbg !10` in the output.

errors_test.go

@@ -17,6 +17,7 @@ import (
 func TestErrors(t *testing.T) {
 	for _, name := range []string{
 		"cgo",
+		"interp",
 		"loader-importcycle",
 		"loader-invaliddep",
 		"loader-invalidpackage",

interp/interpreter.go

@@ -417,6 +417,10 @@ func (r *runner) run(fn *function, params []value, parentMem *memoryView, indent
 				} else {
 					locals[inst.localIndex] = literalValue{uint8(0)}
 				}
+			case callFn.name == "__tinygo_interp_raise_test_error":
+				// Special function that will trigger an error.
+				// This is used to test error reporting.
+				return nil, mem, r.errorAt(inst, errors.New("test error"))
 			case strings.HasSuffix(callFn.name, ".$typeassert"):
 				if r.debug {
 					fmt.Fprintln(os.Stderr, indent+"interface assert:", operands[1:])

testdata/errors/interp.go

@@ -0,0 +1,31 @@
+package main
+
+import _ "unsafe"
+
+func init() {
+	foo()
+}
+
+func foo() {
+	interp_test_error()
+}
+
+// This is a function that always causes an error in interp, for testing.
+//
+//go:linkname interp_test_error __tinygo_interp_raise_test_error
+func interp_test_error()
+
+func main() {
+}
+
+// ERROR: # main
+// ERROR: {{.*testdata[\\/]errors[\\/]interp\.go}}:10:19: test error
+// ERROR:   call void @__tinygo_interp_raise_test_error{{.*}}
+// ERROR: {{}}
+// ERROR: traceback:
+// ERROR: {{.*testdata[\\/]errors[\\/]interp\.go}}:10:19:
+// ERROR:   call void @__tinygo_interp_raise_test_error{{.*}}
+// ERROR: {{.*testdata[\\/]errors[\\/]interp\.go}}:6:5:
+// ERROR:   call void @main.foo{{.*}}
+// ERROR: {{.*testdata[\\/]errors}}:
+// ERROR:   call void @"main.init#1"{{.*}}