proc: return error when calling a non-ptr receiver method on a nil ptr (#4139)

During a call injection if the user tries to call a non-ptr receiver
method on a nil ptr it should receive a nil pointer dereference error.

Fixes #4136

_fixtures/fncall.go

@@ -265,6 +265,8 @@ func main() {
 	var ref strings.Builder
 	fmt.Fprintf(&ref, "blah")
 
+	var nilptrtostruct *astruct
+
 	runtime.Breakpoint() // breakpoint here
 	call1(one, two)
 	fn2clos(2)
@@ -272,5 +274,5 @@ func main() {
 	d.Method()
 	d.Base.Method()
 	x.CallMe()
-	fmt.Println(one, two, zero, call, call0, call2, callexit, callpanic, callbreak, callstacktrace, stringsJoin, intslice, stringslice, comma, a.VRcvr, a.PRcvr, pa, vable_a, vable_pa, pable_pa, fn2clos, fn2glob, fn2valmeth, fn2ptrmeth, fn2nil, ga, escapeArg, a2, square, intcallpanic, onetwothree, curriedAdd, getAStruct, getAStructPtr, getVRcvrableFromAStruct, getPRcvrableFromAStructPtr, getVRcvrableFromAStructPtr, pa2, noreturncall, str, d, x, x2.CallMe(5), longstrs, regabistacktest, regabistacktest2, issue2698.String(), issue3364.String(), regabistacktest3, rast3, floatsum, ref, mul2, mul2ptr, m)
+	fmt.Println(one, two, zero, call, call0, call2, callexit, callpanic, callbreak, callstacktrace, stringsJoin, intslice, stringslice, comma, a.VRcvr, a.PRcvr, pa, vable_a, vable_pa, pable_pa, fn2clos, fn2glob, fn2valmeth, fn2ptrmeth, fn2nil, ga, escapeArg, a2, square, intcallpanic, onetwothree, curriedAdd, getAStruct, getAStructPtr, getVRcvrableFromAStruct, getPRcvrableFromAStructPtr, getVRcvrableFromAStructPtr, pa2, noreturncall, str, d, x, x2.CallMe(5), longstrs, regabistacktest, regabistacktest2, issue2698.String(), issue3364.String(), regabistacktest3, rast3, floatsum, ref, mul2, mul2ptr, m, nilptrtostruct)
 }

pkg/proc/fncall.go

@@ -540,6 +540,10 @@ func funcCallEvalFuncExpr(scope *EvalScope, stack *evalStack, fncall *functionCa
 	if len(fnvar.Children) > 0 && argnum == (len(fncall.formalArgs)-1) {
 		argnum++
 		fncall.receiver = &fnvar.Children[0]
+		_, isptr := fncall.receiver.DwarfType.(*godwarf.PtrType)
+		if fncall.receiver.Addr == 0 && !isptr {
+			return errors.New("nil pointer dereference")
+		}
 		fncall.receiver.Name = astutil.ExprToString(fncall.expr.Fun)
 	}
 

pkg/proc/variables_test.go

@@ -1354,6 +1354,9 @@ func TestCallFunction(t *testing.T) {
 		// Issue 3176
 		{`ref.String()[0]`, []string{`:byte:98`}, nil, 1},
 		{`ref.String()[20]`, nil, errors.New("index out of bounds"), 1},
+
+		// Issue 4136
+		{`nilptrtostruct.VRcvr(0)`, []string{}, errors.New("nil pointer dereference"), 0},
 	}
 
 	var testcases112 = []testCaseCallFunction{