Implement basic reporting facility (#18)

* wip

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>

* save to file after all tasks done

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>

* error out early if the workdir does not exist

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>

* the compiler statistics

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>

* allow compiler statistics per implementation

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>

* save compiler problems

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>

* add flag whether to extract compiler errors

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>

* whitespace

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>

---------

Signed-off-by: Cyrill Leutwiler <bigcyrill@hotmail.com>

crates/compiler/src/lib.rs

@@ -48,8 +48,12 @@ pub struct CompilerInput<T: PartialEq + Eq + Hash> {
 
 /// The generic compilation output configuration.
 pub struct CompilerOutput<T: PartialEq + Eq + Hash> {
+    /// The solc standard JSON input.
     pub input: CompilerInput<T>,
+    /// The produced solc standard JSON output.
     pub output: SolcStandardJsonOutput,
+    /// The error message in case the compiler returns abnormally.
+    pub error: Option<String>,
 }
 
 impl<T> PartialEq for CompilerInput<T>
@@ -110,6 +114,7 @@ where
                         false,
                     ),
                     None,
+                    None,
                 ),
             },
             extra_options: Default::default(),
@@ -156,4 +161,9 @@ where
             input: self.input,
         })
     }
+
+    /// Returns the compiler JSON input.
+    pub fn input(&self) -> SolcStandardJsonInput {
+        self.input.clone()
+    }
 }