scope: advice for unread local variables

Signed-off-by: Jean Privat <jean@pryen.org>

diff --git a/src/semantize/scope.nit b/src/semantize/scope.nit
index 83c5fe4..5048b33 100644 (file)
--- a/src/semantize/scope.nit
+++ b/src/semantize/scope.nit
@@ -36,6 +36,12 @@ class Variable
 
        # Alias of `name`
        redef fun to_s do return self.name
+
+       # The declaration of the variable, if any
+       var location: nullable Location = null
+
+       # Is the local variable not read and need a warning?
+       var warn_unread = false is writable
 end
 
 # Mark where break and continue will branch.
@@ -77,6 +83,18 @@ private class ScopeVisitor
        # All stacked scope. `scopes.first` is the current scope
        private var scopes: List[Scope] = new List[Scope]
 
+       # Shift and check the last scope
+       fun shift_scope
+       do
+               assert not scopes.is_empty
+               var scope = scopes.shift
+               for v in scope.variables.values do
+                       if v.warn_unread then
+                               toolcontext.advice(v.location, "unread-variable", "Warning: local variable {v.name} is never read.")
+                       end
+               end
+       end
+
        # Regiter a local variable.
        # Display an error on toolcontext if a variable with the same name is masked.
        fun register_variable(node: ANode, variable: Variable): Bool
@@ -88,6 +106,7 @@ private class ScopeVisitor
                        return false
                end
                scopes.first.variables[name] = variable
+               variable.location = node.location
                return true
        end
 
@@ -118,7 +137,7 @@ private class ScopeVisitor
                scope.escapemark = escapemark
                scopes.unshift(scope)
                enter_visit(node)
-               scopes.shift
+               shift_scope
        end
 
        # Look for a label `name`.
@@ -232,6 +251,7 @@ redef class APropdef
        do
                var v = new ScopeVisitor(toolcontext)
                v.enter_visit(self)
+               v.shift_scope
        end
 end
 
@@ -257,6 +277,7 @@ redef class AVardeclExpr
                var nid = self.n_id
                var variable = new Variable(nid.text)
                v.register_variable(nid, variable)
+               variable.warn_unread = true # wait for some read mark.
                self.variable = variable
        end
 end
@@ -370,7 +391,7 @@ redef class AForExpr
                self.escapemark = escapemark
                v.enter_visit_block(n_block, escapemark)
 
-               v.scopes.shift
+               v.shift_scope
        end
 end
 
@@ -409,6 +430,7 @@ end
 redef class ACallExpr
        redef fun variable_create(variable)
        do
+               variable.warn_unread = false
                return new AVarExpr.init_avarexpr(n_id)
        end
 end
@@ -423,6 +445,7 @@ end
 redef class ACallReassignExpr
        redef fun variable_create(variable)
        do
+               variable.warn_unread = false
                return new AVarReassignExpr.init_avarreassignexpr(n_id, n_assign_op, n_value)
        end
 end