Provide macro for exporting functions from wasm (#3801)

The macro generates the functions with the signature we expect for wasm
functions. This macro is useful for tests where we need to call into
wasm. Parameter passing is done by SCALE encoding the input and output
parameters.

substrate/core/executor/src/sandbox.rs

@@ -631,11 +631,11 @@ mod tests {
 				call $assert
 			)
 		)
-		"#).unwrap();
+		"#).unwrap().encode();
 
 		assert_eq!(
 			call_wasm(&mut ext, 8, &test_code[..], "test_sandbox", &code).unwrap(),
-			vec![1],
+			true.encode(),
 		);
 	}
 
@@ -673,7 +673,7 @@ mod tests {
 				call $assert
 			)
 		)
-		"#).unwrap();
+		"#).unwrap().encode();
 
 		let res = call_wasm(&mut ext, 8, &test_code[..], "test_exhaust_heap", &code);
 		assert_eq!(res.is_err(), true);
@@ -718,11 +718,11 @@ mod tests {
 				call $assert
 			)
 		)
-		"#).unwrap();
+		"#).unwrap().encode();
 
 		assert_eq!(
 			call_wasm(&mut ext, 8, &test_code[..], "test_sandbox", &code).unwrap(),
-			vec![1],
+			true.encode(),
 		);
 	}
 
@@ -752,11 +752,11 @@ mod tests {
 				)
 			)
 		)
-		"#).unwrap();
+		"#).unwrap().encode();
 
 		assert_eq!(
 			call_wasm(&mut ext, 8, &test_code[..], "test_sandbox_args", &code).unwrap(),
-			vec![1],
+			true.encode(),
 		);
 	}
 
@@ -774,11 +774,11 @@ mod tests {
 				)
 			)
 		)
-		"#).unwrap();
+		"#).unwrap().encode();
 
 		assert_eq!(
 			call_wasm(&mut ext, 8, &test_code[..], "test_sandbox_return_val", &code).unwrap(),
-			vec![1],
+			true.encode(),
 		);
 	}
 
@@ -794,11 +794,11 @@ mod tests {
 			(func (export "call")
 			)
 		)
-		"#).unwrap();
+		"#).unwrap().encode();
 
 		assert_eq!(
 			call_wasm(&mut ext, 8, &test_code[..], "test_sandbox_instantiate", &code).unwrap(),
-			vec![1],
+			1u8.encode(),
 		);
 	}
 
@@ -808,11 +808,11 @@ mod tests {
 		let test_code = WASM_BINARY;
 
 		// Corrupted wasm file
-		let code = &[0, 0, 0, 0, 1, 0, 0, 0];
+		let code = vec![0u8, 0, 0, 0, 1, 0, 0, 0].encode();
 
 		assert_eq!(
-			call_wasm(&mut ext, 8, &test_code[..], "test_sandbox_instantiate", code).unwrap(),
-			vec![1],
+			call_wasm(&mut ext, 8, &test_code[..], "test_sandbox_instantiate", &code).unwrap(),
+			1u8.encode(),
 		);
 	}
 
@@ -831,11 +831,11 @@ mod tests {
 
 			(start $start)
 		)
-		"#).unwrap();
+		"#).unwrap().encode();
 
 		assert_eq!(
 			call_wasm(&mut ext, 8, &test_code[..], "test_sandbox_instantiate", &code).unwrap(),
-			vec![0],
+			0u8.encode(),
 		);
 	}
 
@@ -855,11 +855,11 @@ mod tests {
 
 			(start $start)
 		)
-		"#).unwrap();
+		"#).unwrap().encode();
 
 		assert_eq!(
 			call_wasm(&mut ext, 8, &test_code[..], "test_sandbox_instantiate", &code).unwrap(),
-			vec![2],
+			2u8.encode(),
 		);
 	}
 }