compiler: disallow most types in //go:wasmimport

This is for compatibility with upstream Go.
See https://github.com/golang/go/issues/59149 for more context.

compiler/testdata/errors.go

@@ -1 +1,43 @@
 package main
+
+import "unsafe"
+
+//go:wasmimport modulename empty
+func empty()
+
+// ERROR: can only use //go:wasmimport on declarations
+//
+//go:wasmimport modulename implementation
+func implementation() {
+}
+
+type Uint uint32
+
+//go:wasmimport modulename validparam
+func validparam(a int32, b uint64, c float64, d unsafe.Pointer, e Uint)
+
+// ERROR: //go:wasmimport modulename invalidparam: unsupported parameter type int
+// ERROR: //go:wasmimport modulename invalidparam: unsupported parameter type string
+// ERROR: //go:wasmimport modulename invalidparam: unsupported parameter type []byte
+// ERROR: //go:wasmimport modulename invalidparam: unsupported parameter type *int32
+//
+//go:wasmimport modulename invalidparam
+func invalidparam(a int, b string, c []byte, d *int32)
+
+//go:wasmimport modulename validreturn
+func validreturn() int32
+
+// ERROR: //go:wasmimport modulename manyreturns: too many return values
+//
+//go:wasmimport modulename manyreturns
+func manyreturns() (int32, int32)
+
+// ERROR: //go:wasmimport modulename invalidreturn: unsupported result type int
+//
+//go:wasmimport modulename invalidreturn
+func invalidreturn() int
+
+// ERROR: //go:wasmimport modulename invalidUnsafePointerReturn: unsupported result type unsafe.Pointer
+//
+//go:wasmimport modulename invalidUnsafePointerReturn
+func invalidUnsafePointerReturn() unsafe.Pointer

compiler/testdata/pragma.go

@@ -62,10 +62,6 @@ func exportedFunctionInSection() {
 //go:wasmimport modulename import1
 func declaredImport()
 
-//go:wasmimport modulename import2
-func definedImport() {
-}
-
 // This function should not: it's only a declaration and not a definition.
 //
 //go:section .special_function_section

compiler/testdata/pragma.ll

@@ -62,12 +62,6 @@ entry:
 
 declare void @main.declaredImport() #7
 
-; Function Attrs: nounwind
-define hidden void @main.definedImport(ptr %context) unnamed_addr #2 {
-entry:
-  ret void
-}
-
 declare void @main.undefinedFunctionNotInSection(ptr) #1
 
 attributes #0 = { allockind("alloc,zeroed") allocsize(0) "alloc-family"="runtime.alloc" "target-features"="+bulk-memory,+nontrapping-fptoint,+sign-ext" }