compiler: implement recover() built-in function

testdata/corpus.yaml

@@ -107,6 +107,8 @@
   - pkg: blowfish
   - pkg: bn256
   - pkg: cast5
+  - pkg: chacha20
+    skipwasi: true # needs recover
   - pkg: chacha20poly1305
   - pkg: curve25519
   - pkg: ed25519
@@ -129,7 +131,6 @@
   - pkg: tea
   - pkg: twofish
   - pkg: xtea
-  #- pkg: chacha20 # panic: chacha20: SetCounter attempted to rollback counter
   #- pkg: cryptobyte # panic: unimplemented: reflect.OverflowInt()
   #- pkg: salsa20/salsa # panic: runtime error: index out of range
   #- pkg: sha3 # panic: unimplemented: (reflect.Type).NumMethod()
@@ -209,15 +210,27 @@
   tags: noasm appengine
   subdirs:
   - pkg: blas/blas32
+  - pkg: blas/blas64
+    skipwasi: true # needs recover
   - pkg: blas/cblas64
   - pkg: blas/cblas128
+  - pkg: blas/gonum
+    skipwasi: true # needs recover
+  - pkg: cmplxs
+    skipwasi: true # needs recover
   - pkg: cmplxs/cscalar
+  - pkg: diff/fd
+    skipwasi: true # needs recover
   - pkg: dsp/window
+  - pkg: floats
+    skipwasi: true # needs recover
   - pkg: floats/scalar
   - pkg: integrate
   - pkg: integrate/quad
   - pkg: internal/cmplx64
   - pkg: internal/testrand
+  - pkg: interp
+    skipwasi: true # needs recover
   - pkg: lapack/gonum
     skipwasi: true # takes too long
     slow: true
@@ -236,15 +249,9 @@
     slow: true
   - pkg: stat/samplemv
     skipwasi: true # takes too long
-  #- pkg: blas/blas64 # -- TestDasum panic: blas: n < 0
-  #- pkg: blas/gonum # -- panic: blas: n < 0
-  #- pkg: cmplxs # -- TestAdd panic: cmplxs: slice lengths do not match
-  #- pkg: diff/fd # -- panic: fd: slice length mismatch
-  #- pkg: floats # -- panic: floats: destination slice length does not match input
   #- pkg: graph # ld.lld-11:  -- error: undefined symbol: reflect.mapiterkey (among other reflect errors)
   #- pkg: graph/topo # -- Reflect: Same as above
   #- pkg: internal/math32 # -- /usr/local/go/src/testing/quick/quick.go:273:11: fType.NumOut undefined (type reflect.Type has no field or method NumOut)
-  #- pkg: interp # -- panic: interp: input slices have different lengths
   #- pkg: mat # -- panic: mat: row index out of range
   #- pkg: num/dual # TestFormat unexpected result for fmt.Sprintf("%#v", T{Real:1.1, Emag:2.1}): got:"T{Real:1.1, Emag:2.1}", want:"dual.Number{Real:1.1, Emag:2.1}"    unexpected result for fmt.Sprintf("%#v", T{Real:-1.1, Emag:-2.1}): got:"T{Real:-1.1, Emag:-2.1}", want:"dual.Number{Real:-1.1, Emag:-2.1}"
   #- pkg: num/dualcmplx # TestFormat (similar to above)

testdata/recover.go

@@ -0,0 +1,99 @@
+package main
+
+func main() {
+	println("# simple recover")
+	recoverSimple()
+
+	println("\n# recover with result")
+	result := recoverWithResult()
+	println("result:", result)
+
+	println("\n# nested defer frame")
+	nestedDefer()
+
+	println("\n# nested panic: panic inside recover")
+	nestedPanic()
+
+	println("\n# panic inside defer")
+	panicInsideDefer()
+
+	println("\n# panic replace")
+	panicReplace()
+}
+
+func recoverSimple() {
+	defer func() {
+		println("recovering...")
+		printitf("recovered:", recover())
+	}()
+	println("running panic...")
+	panic("panic")
+}
+
+func recoverWithResult() (result int) {
+	defer func() {
+		printitf("recovered:", recover())
+	}()
+	result = 3
+	println("running panic...")
+	panic("panic")
+}
+
+func nestedDefer() {
+	defer func() {
+		printitf("recovered:", recover())
+	}()
+
+	func() {
+		// The defer here doesn't catch the panic using recover(), so the outer
+		// panic should do that.
+		defer func() {
+			println("deferred nested function")
+		}()
+		panic("panic")
+	}()
+	println("unreachable")
+}
+
+func nestedPanic() {
+	defer func() {
+		printitf("recovered 1:", recover())
+
+		defer func() {
+			printitf("recovered 2:", recover())
+		}()
+
+		panic("foo")
+	}()
+	panic("panic")
+}
+
+func panicInsideDefer() {
+	defer func() {
+		printitf("recovered:", recover())
+	}()
+	defer func() {
+		panic("panic")
+	}()
+}
+
+func panicReplace() {
+	defer func() {
+		printitf("recovered:", recover())
+	}()
+	defer func() {
+		println("panic 2")
+		panic("panic 2")
+	}()
+	println("panic 1")
+	panic("panic 1")
+}
+
+func printitf(msg string, itf interface{}) {
+	switch itf := itf.(type) {
+	case string:
+		println(msg, itf)
+	default:
+		println(msg, itf)
+	}
+}

testdata/recover.txt

@@ -0,0 +1,25 @@
+# simple recover
+running panic...
+recovering...
+recovered: panic
+
+# recover with result
+running panic...
+recovered: panic
+result: 3
+
+# nested defer frame
+deferred nested function
+recovered: panic
+
+# nested panic: panic inside recover
+recovered 1: panic
+recovered 2: foo
+
+# panic inside defer
+recovered: panic
+
+# panic replace
+panic 1
+panic 2
+recovered: panic 2