github.com/amarpal/go-tools@v0.0.0-20240422043104-40142f59f616/go/ir/irutil/testdata/switches.go

//go:build ignore
// +build ignore

package main

// This file is the input to TestSwitches in switch_test.go.
// Each multiway conditional with constant or type cases (Switch)
// discovered by Switches is printed, and compared with the
// comments.
//
// The body of each case is printed as the value of its first
// instruction.

// -------- Value switches --------

func four() int { return 4 }

// A non-constant case makes a switch "impure", but its pure
// cases form two separate switches.
func SwitchWithNonConstantCase(x int) {
	// switch t12 {
	// case t1: Call <()> print t2
	// case t3: Call <()> print t5
	// case t4: Call <()> print t5
	// default: BinOp <bool> {==} t30 t31
	// }

	// switch t36 {
	// case t7: Call <()> print t8
	// case t9: Call <()> print t10
	// default: Call <()> print t11
	// }
	switch x {
	case 1:
		print(1)
	case 2, 3:
		print(23)
	case four():
		print(3)
	case 5:
		print(5)
	case 6:
		print(6)
	}
	print("done")
}

// Switches may be found even where the source
// program doesn't have a switch statement.

func ImplicitSwitches(x, y int) {
	// switch t13 {
	// case t1: Call <()> print t4
	// case t2: Call <()> print t4
	// default: BinOp <bool> {<} t28 t3
	// }
	if x == 1 || 2 == x || x < 5 {
		print(12)
	}

	// switch t25 {
	// case t5: Call <()> print t7
	// case t6: Call <()> print t7
	// default: BinOp <bool> {==} t50 t51
	// }
	if x == 3 || 4 == x || x == y {
		print(34)
	}

	// Not a switch: no consistent variable.
	if x == 5 || y == 6 {
		print(56)
	}

	// Not a switch: only one constant comparison.
	if x == 7 || x == y {
		print(78)
	}
}

func IfElseBasedSwitch(x int) {
	// switch t6 {
	// case t1: Call <()> print t2
	// case t3: Call <()> print t4
	// default: Call <()> print t5
	// }
	if x == 1 {
		print(1)
	} else if x == 2 {
		print(2)
	} else {
		print("else")
	}
}

func GotoBasedSwitch(x int) {
	// switch t6 {
	// case t1: Call <()> print t4
	// case t2: Call <()> print t5
	// default: Call <()> print t3
	// }
	if x == 1 {
		goto L1
	}
	if x == 2 {
		goto L2
	}
	print("else")
L1:
	print(1)
	goto end
L2:
	print(2)
end:
}

func SwitchInAForLoop(x, y int) {
	// switch t13 {
	// case t2: Call <()> print t3
	// case t4: Call <()> print t5
	// default: BinOp <bool> {==} t31 t30
	// }
loop:
	for {
		print("head")
		switch x {
		case 1:
			print(1)
			break loop
		case 2:
			print(2)
			break loop
		case y:
			print(3)
			break loop
		}
	}
}

// This case is a switch in a for-loop, both constructed using goto.
// As before, the default case points back to the block containing the
// switch, but that's ok.
func SwitchInAForLoopUsingGoto(x int) {
	// switch t10 {
	// case t2: Call <()> print t4
	// case t3: Call <()> print t5
	// default: BinOp <bool> {==} t10 t2
	// }
loop:
	print("head")
	if x == 1 {
		goto L1
	}
	if x == 2 {
		goto L2
	}
	goto loop
L1:
	print(1)
	goto end
L2:
	print(2)
end:
}

func UnstructuredSwitchInAForLoop(x int) {
	// switch t9 {
	// case t1: Call <()> print t2
	// case t3: BinOp <bool> {==} t9 t1
	// default: Call <()> print t4
	// }
	for {
		if x == 1 {
			print(1)
			return
		}
		if x == 2 {
			continue
		}
		break
	}
	print("end")
}

func CaseWithMultiplePreds(x int) {
	for {
		if x == 1 {
			print(1)
			return
		}
	loop:
		// This block has multiple predecessors,
		// so can't be treated as a switch case.
		if x == 2 {
			goto loop
		}
		break
	}
	print("end")
}

func DuplicateConstantsAreNotEliminated(x int) {
	// switch t7 {
	// case t1: Call <()> print t2
	// case t3: Call <()> print t4
	// case t5: Call <()> print t6
	// default: Return
	// }
	if x == 1 {
		print(1)
	} else if x == 1 { // duplicate => unreachable
		print("1a")
	} else if x == 2 {
		print(2)
	}
}

// Interface values (created by comparisons) are not constants,
// so ConstSwitch.X is never of interface type.
func MakeInterfaceIsNotAConstant(x interface{}) {
	if x == "foo" {
		print("foo")
	} else if x == 1 {
		print(1)
	}
}

func ZeroInitializedVarsAreConstants(x int) {
	// switch t6 {
	// case t5: Call <()> print t1
	// case t2: Call <()> print t3
	// default: Call <()> print t4
	// }
	var zero int // SSA construction replaces zero with 0
	if x == zero {
		print(1)
	} else if x == 2 {
		print(2)
	}
	print("end")
}

// -------- Type switches --------

// NB, potentially fragile reliance on register number.
func AdHocTypeSwitch(x interface{}) {
	// switch t2.(type) {
	// case t4 int: Call <()> println t8
	// case t13 string: Call <()> println t16
	// default: Call <()> print t1
	// }
	if i, ok := x.(int); ok {
		println(i)
	} else if s, ok := x.(string); ok {
		println(s)
	} else {
		print("default")
	}
}