Set 'isLazy' to true in the NFA, if the postfixNode has the flag set

regex/compile.go

@@ -945,6 +945,10 @@ func shuntingYard(re string, flags ...ReFlag) ([]postfixNode, error) {
 			}
 			outQueue[idx].startReps = startRangeNum
 			outQueue[idx].endReps = endRangeNum
+			if i < len(re_postfix)-1 && re_postfix[i+1] == '?' { // lazy repitition
+				outQueue[idx].isLazy = true
+				i++
+			}
 		}
 		if c == '(' || c == nonCapLparenRune {
 			opStack = append(opStack, c)
@@ -1238,6 +1242,9 @@ func thompson(re []postfixNode) (Reg, error) {
 			if err != nil {
 				return Reg{}, err
 			}
+			if c.isLazy {
+				stateToAdd.isLazy = true
+			}
 			nfa = append(nfa, stateToAdd)
 		case plusNode: // a+ is equivalent to aa*
 			s1 := mustPop(&nfa)
@@ -1245,6 +1252,9 @@ func thompson(re []postfixNode) (Reg, error) {
 			if err != nil {
 				return Reg{}, err
 			}
+			if c.isLazy {
+				s2.isLazy = true
+			}
 			s1 = concatenate(s1, s2)
 			nfa = append(nfa, s1)
 		case questionNode: // ab? is equivalent to a(b|)
@@ -1256,6 +1266,9 @@ func thompson(re []postfixNode) (Reg, error) {
 			if err != nil {
 				return Reg{}, err
 			}
+			if c.isLazy {
+				s2.isLazy = true
+			}
 			nfa = append(nfa, s2)
 		case pipeNode:
 			// A pipe operator doesn't actually need either operand to be present. If an operand isn't present,
@@ -1311,6 +1324,9 @@ func thompson(re []postfixNode) (Reg, error) {
 				if err != nil {
 					return Reg{}, err
 				}
+				if c.isLazy {
+					s2.isLazy = true
+				}
 				stateToAdd = concatenate(stateToAdd, s2)
 			} else { // Case 2
 				for i := c.startReps; i < c.endReps; i++ {
@@ -1318,6 +1334,9 @@ func thompson(re []postfixNode) (Reg, error) {
 					if err != nil {
 						return Reg{}, fmt.Errorf("error processing bounded repetition")
 					}
+					if c.isLazy {
+						tmp.isLazy = true
+					}
 					stateToAdd = concatenate(stateToAdd, tmp)
 				}
 			}