+++ /dev/null
-// +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 SimpleSwitch(x, y int) {
- // switch x {
- // case 1:int: print(1:int)
- // case 2:int: print(23:int)
- // case 3:int: print(23:int)
- // case 4:int: print(3:int)
- // default: x == y
- // }
- switch x {
- case 1:
- print(1)
- case 2, 3:
- print(23)
- fallthrough
- case 4:
- print(3)
- default:
- print(4)
- case y:
- print(5)
- }
- print(6)
-}
-
-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 x {
- // case 1:int: print(1:int)
- // case 2:int: print(23:int)
- // case 3:int: print(23:int)
- // default: four()
- // }
-
- // switch x {
- // case 5:int: print(5:int)
- // case 6:int: print(6:int)
- // default: print("done":string)
- // }
- 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 x {
- // case 1:int: print(12:int)
- // case 2:int: print(12:int)
- // default: x < 5:int
- // }
- if x == 1 || 2 == x || x < 5 {
- print(12)
- }
-
- // switch x {
- // case 3:int: print(34:int)
- // case 4:int: print(34:int)
- // default: x == y
- // }
- 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 x {
- // case 1:int: print(1:int)
- // case 2:int: print(2:int)
- // default: print("else":string)
- // }
- if x == 1 {
- print(1)
- } else if x == 2 {
- print(2)
- } else {
- print("else")
- }
-}
-
-func GotoBasedSwitch(x int) {
- // switch x {
- // case 1:int: print(1:int)
- // case 2:int: print(2:int)
- // default: print("else":string)
- // }
- if x == 1 {
- goto L1
- }
- if x == 2 {
- goto L2
- }
- print("else")
-L1:
- print(1)
- goto end
-L2:
- print(2)
-end:
-}
-
-func SwitchInAForLoop(x int) {
- // switch x {
- // case 1:int: print(1:int)
- // case 2:int: print(2:int)
- // default: print("head":string)
- // }
-loop:
- for {
- print("head")
- switch x {
- case 1:
- print(1)
- break loop
- case 2:
- print(2)
- 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 x {
- // case 1:int: print(1:int)
- // case 2:int: print(2:int)
- // default: print("head":string)
- // }
-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 x {
- // case 1:int: print(1:int)
- // case 2:int: x == 1:int
- // default: print("end":string)
- // }
- 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 x {
- // case 1:int: print(1:int)
- // case 1:int: print("1a":string)
- // case 2:int: print(2:int)
- // 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 x {
- // case 0:int: print(1:int)
- // case 2:int: print(2:int)
- // default: print("end":string)
- // }
- var zero int // SSA construction replaces zero with 0
- if x == zero {
- print(1)
- } else if x == 2 {
- print(2)
- }
- print("end")
-}
-
-// -------- Select --------
-
-// NB, potentially fragile reliance on register number.
-func SelectDesugarsToSwitch(ch chan int) {
- // switch t1 {
- // case 0:int: extract t0 #2
- // case 1:int: println(0:int)
- // case 2:int: println(1:int)
- // default: println("default":string)
- // }
- select {
- case x := <-ch:
- println(x)
- case <-ch:
- println(0)
- case ch <- 1:
- println(1)
- default:
- println("default")
- }
-}
-
-// NB, potentially fragile reliance on register number.
-func NonblockingSelectDefaultCasePanics(ch chan int) {
- // switch t1 {
- // case 0:int: extract t0 #2
- // case 1:int: println(0:int)
- // case 2:int: println(1:int)
- // default: make interface{} <- string ("blocking select m...":string)
- // }
- select {
- case x := <-ch:
- println(x)
- case <-ch:
- println(0)
- case ch <- 1:
- println(1)
- }
-}
-
-// -------- Type switches --------
-
-// NB, reliance on fragile register numbering.
-func SimpleTypeSwitch(x interface{}) {
- // switch x.(type) {
- // case t3 int: println(x)
- // case t7 bool: println(x)
- // case t10 string: println(t10)
- // default: println(x)
- // }
- switch y := x.(type) {
- case nil:
- println(y)
- case int, bool:
- println(y)
- case string:
- println(y)
- default:
- println(y)
- }
-}
-
-// NB, potentially fragile reliance on register number.
-func DuplicateTypesAreNotEliminated(x interface{}) {
- // switch x.(type) {
- // case t1 string: println(1:int)
- // case t5 interface{}: println(t5)
- // case t9 int: println(3:int)
- // default: return
- // }
- switch y := x.(type) {
- case string:
- println(1)
- case interface{}:
- println(y)
- case int:
- println(3) // unreachable!
- }
-}
-
-// NB, potentially fragile reliance on register number.
-func AdHocTypeSwitch(x interface{}) {
- // switch x.(type) {
- // case t1 int: println(t1)
- // case t5 string: println(t5)
- // default: print("default":string)
- // }
- if i, ok := x.(int); ok {
- println(i)
- } else if s, ok := x.(string); ok {
- println(s)
- } else {
- print("default")
- }
-}
projects / dotfiles / .git / blobdiff