test: add extra typeswitch tests that cause duplicate cases

Augmented some of the typeswitch*.go tests so that some instantiations
have duplicate cases, in order to ensure we're testing that.

Spacing changes in the tests are due to gofmt.

Change-Id: I5d3678813505c520c544281d4ac8a62ce7e236ad
Reviewed-on: https://go-review.googlesource.com/c/go/+/370155
Trust: Dan Scales <danscales@google.com>
Run-TryBot: Dan Scales <danscales@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

test/run.go

@@ -2183,6 +2183,10 @@ var unifiedFailures = setOf(
 	"fixedbugs/issue49767.go",  // unified IR doesn't report channel element too large
 	"fixedbugs/issue49814.go",  // unified IR doesn't report array type too large
 	"typeparam/issue50002.go",  // pure stenciling leads to a static type assertion error
+	"typeparam/typeswitch1.go", // duplicate case failure due to stenciling
+	"typeparam/typeswitch2.go", // duplicate case failure due to stenciling
+	"typeparam/typeswitch3.go", // duplicate case failure due to stenciling
+	"typeparam/typeswitch4.go", // duplicate case failure due to stenciling
 )
 
 func setOf(keys ...string) map[string]bool {

test/typeparam/typeswitch1.go

@@ -14,7 +14,7 @@ func f[T any](i interface{}) {
 		println("int")
 	case int32, int16:
 		println("int32/int16")
-	case struct { a, b T }:
+	case struct{ a, b T }:
 		println("struct{T,T}")
 	default:
 		println("other")
@@ -24,6 +24,8 @@ func main() {
 	f[float64](float64(6))
 	f[float64](int(7))
 	f[float64](int32(8))
-	f[float64](struct{a, b float64}{a:1, b:2})
+	f[float64](struct{ a, b float64 }{a: 1, b: 2})
 	f[float64](int8(9))
+	f[int32](int32(7))
+	f[int](int32(7))
 }

test/typeparam/typeswitch1.out

@@ -3,3 +3,5 @@ int
 int32/int16
 struct{T,T}
 other
+T
+int32/int16

test/typeparam/typeswitch2.go

@@ -28,4 +28,6 @@ func main() {
 	f[float64](int32(8))
 	f[float64](struct{ a, b float64 }{a: 1, b: 2})
 	f[float64](int8(9))
+	f[int32](int32(7))
+	f[int](int32(7))
 }

test/typeparam/typeswitch2.out

@@ -3,3 +3,5 @@ int 7
 int32/int16 8
 struct{T,T} +1.000000e+000 +2.000000e+000
 other 9
+T 7
+int32/int16 7

test/typeparam/typeswitch3.go

@@ -6,16 +6,18 @@
 
 package main
 
-type I interface { foo() int }
+type I interface{ foo() int }
 
 type myint int
 
 func (x myint) foo() int { return int(x) }
 
 type myfloat float64
+
 func (x myfloat) foo() int { return int(x) }
 
 type myint32 int32
+
 func (x myint32) foo() int { return int(x) }
 
 func f[T I](i I) {
@@ -32,4 +34,7 @@ func main() {
 	f[myfloat](myint(6))
 	f[myfloat](myfloat(7))
 	f[myfloat](myint32(8))
+	f[myint32](myint32(8))
+	f[myint32](myfloat(7))
+	f[myint](myint32(9))
 }

test/typeparam/typeswitch3.out

@@ -1,3 +1,6 @@
 myint 6
 T 7
 other 8
+T 8
+other 7
+other 9

test/typeparam/typeswitch4.go

@@ -6,16 +6,18 @@
 
 package main
 
-type I interface { foo() int }
+type I interface{ foo() int }
 
 type myint int
 
-func (x myint) foo() int {return int(x)}
+func (x myint) foo() int { return int(x) }
 
 type myfloat float64
-func (x myfloat) foo() int {return int(x)}
+
+func (x myfloat) foo() int { return int(x) }
 
 type myint32 int32
+
 func (x myint32) foo() int { return int(x) }
 
 func f[T I](i I) {
@@ -30,4 +32,7 @@ func main() {
 	f[myfloat](myint(6))
 	f[myfloat](myfloat(7))
 	f[myfloat](myint32(8))
+	f[myint32](myint32(9))
+	f[myint](myint32(10))
+	f[myint](myfloat(42))
 }

test/typeparam/typeswitch4.out

@@ -1,3 +1,6 @@
 other 6
 T/myint32 7
 T/myint32 8
+T/myint32 9
+T/myint32 10
+other 42