Still working on type propagation...

33 files changed, 366 insertions, 180 deletions

diff --git a/src/core/src/tonkadur/fate/v1/lang/computation/AmbiguousWord.java b/src/core/src/tonkadur/fate/v1/lang/computation/AmbiguousWord.java
index 60f5efb..5fc97ac 100644
--- a/src/core/src/tonkadur/fate/v1/lang/computation/AmbiguousWord.java
+++ b/src/core/src/tonkadur/fate/v1/lang/computation/AmbiguousWord.java
@@ -5,8 +5,8 @@ import tonkadur.parser.Origin;
 import tonkadur.fate.v1.parser.ParserData;
 
 import tonkadur.fate.v1.lang.type.Type;
+import tonkadur.fate.v1.lang.type.FutureType;
 
-import tonkadur.fate.v1.lang.meta.ComputationVisitor;
 import tonkadur.fate.v1.lang.meta.Computation;
 import tonkadur.fate.v1.lang.meta.VariableFromWord;
 
@@ -41,7 +41,7 @@ public class AmbiguousWord extends Computation
       final String as_string
    )
    {
-      super(origin, Type.ANY);
+      super(origin, new FutureType(origin, new ArrayList<>()));
 
       this.parser = parser;
       this.as_string = as_string;
@@ -63,7 +63,7 @@ public class AmbiguousWord extends Computation
    {
       if (result == null)
       {
-         return Type.ANY;
+         return type;
       }
 
       return result.get_type();
@@ -82,12 +82,16 @@ public class AmbiguousWord extends Computation
 
          System.exit(-1);
       }
+
+      type.resolve_to(result.get_type());
    }
 
    @Override
    public void expect_string ()
    {
       result = Constant.build_string(get_origin(), as_string);
+
+      type.resolve_to(result.get_type());
    }
 
    public String get_value_as_string ()
diff --git a/src/core/src/tonkadur/fate/v1/lang/computation/CondValue.java b/src/core/src/tonkadur/fate/v1/lang/computation/CondValue.java
index b7683d2..7d5b4e3 100644
--- a/src/core/src/tonkadur/fate/v1/lang/computation/CondValue.java
+++ b/src/core/src/tonkadur/fate/v1/lang/computation/CondValue.java
@@ -50,26 +50,6 @@ public class CondValue extends Computation
    )
    throws ParsingError
    {
-      Type hint;
-
-      hint = null;
-
-      for (final Cons<Computation, Computation> entry: branches)
-      {
-         if (entry.get_cdr().get_type().can_be_used_as(Type.STRING))
-         {
-            hint = Type.STRING;
-
-            break;
-         }
-         else if (entry.get_cdr().get_type() != Type.ANY)
-         {
-            hint = entry.get_cdr().get_type();
-
-            break;
-         }
-      }
-
       for (final Cons<Computation, Computation> entry: branches)
       {
          entry.get_car().expect_non_string();
@@ -82,12 +62,7 @@ public class CondValue extends Computation
          }
       }
 
-      if (hint == null)
-      {
-         hint = new FutureType(origin, new ArrayList<Type>());
-      }
-
-      return new CondValue(origin, hint, branches);
+      return new CondValue(origin, new FutureType(origin), branches);
    }
 
    /**** Accessors ************************************************************/
@@ -95,52 +70,46 @@ public class CondValue extends Computation
    public void expect_non_string ()
    throws ParsingError
    {
-      if (get_type() instanceof FutureType)
-      {
-         final Computation a;
-         Type hint;
-
-         a = branches.get(0).get_cdr();
+      final Computation a;
+      Type hint;
 
-         a.expect_non_string();
+      a = branches.get(0).get_cdr();
 
-         hint = a.get_type();
+      a.expect_non_string();
 
-         for (final Cons<Computation, Computation> entry: branches)
-         {
-            entry.get_cdr().expect_non_string();
+      hint = a.get_type();
 
-            hint = RecurrentChecks.assert_can_be_used_as(entry.get_cdr(), hint);
-         }
+      for (final Cons<Computation, Computation> entry: branches)
+      {
+         entry.get_cdr().expect_non_string();
 
-         ((FutureType) get_type()).resolve_to(hint);
+         hint = RecurrentChecks.assert_can_be_used_as(entry.get_cdr(), hint);
       }
+
+      ((FutureType) get_type()).resolve_to(hint);
    }
 
    @Override
    public void expect_string ()
    throws ParsingError
    {
-      if (get_type() instanceof FutureType)
-      {
-         final Computation a;
-         Type hint;
-
-         a = branches.get(0).get_cdr();
+      final Computation a;
+      Type hint;
 
-         a.expect_non_string();
+      a = branches.get(0).get_cdr();
 
-         hint = a.get_type();
+      a.expect_non_string();
 
-         for (final Cons<Computation, Computation> entry: branches)
-         {
-            entry.get_cdr().expect_non_string();
+      hint = a.get_type();
 
-            hint = RecurrentChecks.assert_can_be_used_as(entry.get_cdr(), hint);
-         }
+      for (final Cons<Computation, Computation> entry: branches)
+      {
+         entry.get_cdr().expect_non_string();
 
-         ((FutureType) get_type()).resolve_to(hint);
+         hint = RecurrentChecks.assert_can_be_used_as(entry.get_cdr(), hint);
       }
+
+      ((FutureType) get_type()).resolve_to(hint);
    }
 
    @Override
diff --git a/src/core/src/tonkadur/fate/v1/lang/computation/ExtraComputationInstance.java b/src/core/src/tonkadur/fate/v1/lang/computation/ExtraComputationInstance.java
index 7cb5178..43d733a 100644
--- a/src/core/src/tonkadur/fate/v1/lang/computation/ExtraComputationInstance.java
+++ b/src/core/src/tonkadur/fate/v1/lang/computation/ExtraComputationInstance.java
@@ -45,6 +45,12 @@ public class ExtraComputationInstance extends GenericComputation
    )
    throws ParsingError
    {
+      RecurrentChecks.propagate_expected_types
+      (
+         parameters,
+         computation.get_signature()
+      );
+
       RecurrentChecks.assert_computations_matches_signature
       (
          origin,
diff --git a/src/core/src/tonkadur/fate/v1/lang/computation/FieldAccess.java b/src/core/src/tonkadur/fate/v1/lang/computation/FieldAccess.java
index 5096ff8..2bb24fd 100644
--- a/src/core/src/tonkadur/fate/v1/lang/computation/FieldAccess.java
+++ b/src/core/src/tonkadur/fate/v1/lang/computation/FieldAccess.java
@@ -59,6 +59,8 @@ public class FieldAccess extends Computation
    {
       Type current_type;
 
+      parent.expect_non_string();
+
       current_type = parent.get_type();
 
       while (current_type.get_act_as_type().equals(PointerType.ARCHETYPE))
diff --git a/src/core/src/tonkadur/fate/v1/lang/computation/IfElseValue.java b/src/core/src/tonkadur/fate/v1/lang/computation/IfElseValue.java
index 0097537..6a3e726 100644
--- a/src/core/src/tonkadur/fate/v1/lang/computation/IfElseValue.java
+++ b/src/core/src/tonkadur/fate/v1/lang/computation/IfElseValue.java
@@ -51,18 +51,49 @@ public class IfElseValue extends Computation
    )
    throws ParsingError
    {
-      final Type type;
+      condition.expect_non_string();
 
       RecurrentChecks.assert_can_be_used_as(condition, Type.BOOL);
 
-      type =
-         RecurrentChecks.assert_can_be_used_as(if_false, if_true.get_type());
-
-      return new IfElseValue(origin, type, condition, if_true, if_false);
+      return
+         new IfElseValue
+         (
+            origin,
+            new FutureType(origin),
+            condition,
+            if_true,
+            if_false
+         );
    }
 
    /**** Accessors ************************************************************/
    @Override
+   public void expect_non_string ()
+   throws ParsingError
+   {
+      if_true.expect_non_string();
+      if_false.expect_non_string();
+
+      ((FutureType) get_type()).resolve_to
+      (
+         RecurrentChecks.assert_can_be_used_as(if_false, if_true.get_type())
+      );
+   }
+
+   @Override
+   public void expect_string ()
+   throws ParsingError
+   {
+      if_true.expect_string();
+      if_false.expect_string();
+
+      ((FutureType) get_type()).resolve_to
+      (
+         RecurrentChecks.assert_can_be_used_as(if_false, if_true.get_type())
+      );
+   }
+
+   @Override
    public void get_visited_by (final ComputationVisitor cv)
    throws Throwable
    {
diff --git a/src/core/src/tonkadur/fate/v1/lang/computation/LambdaExpression.java b/src/core/src/tonkadur/fate/v1/lang/computation/LambdaExpression.java
index 7ea988b..fa9aec7 100644
--- a/src/core/src/tonkadur/fate/v1/lang/computation/LambdaExpression.java
+++ b/src/core/src/tonkadur/fate/v1/lang/computation/LambdaExpression.java
@@ -52,6 +52,11 @@ public class LambdaExpression extends Computation
       final List<Type> signature;
       final LambdaType type;
 
+      // TODO: is there any way to avoid that? Finding out the expected type
+      // of the lambda expression and using the returned type as a basis for
+      // what is expected?
+      function.expect_string();
+
       signature = new ArrayList<Type>();
 
       for (final Variable v: parameters)
diff --git a/src/core/src/tonkadur/fate/v1/lang/computation/Let.java b/src/core/src/tonkadur/fate/v1/lang/computation/Let.java
index f5be874..06b5c8a 100644
--- a/src/core/src/tonkadur/fate/v1/lang/computation/Let.java
+++ b/src/core/src/tonkadur/fate/v1/lang/computation/Let.java
@@ -44,6 +44,20 @@ public class Let extends Computation
 
    /**** Accessors ************************************************************/
    @Override
+   public void expect_non_string ()
+   throws ParsingError
+   {
+      computation.expect_non_string();
+   }
+
+   @Override
+   public void expect_string ()
+   throws ParsingError
+   {
+      computation.expect_string();
+   }
+
+   @Override
    public void get_visited_by (final ComputationVisitor cv)
    throws Throwable
    {
diff --git a/src/core/src/tonkadur/fate/v1/lang/computation/SetFieldsComputation.java b/src/core/src/tonkadur/fate/v1/lang/computation/SetFieldsComputation.java
index 84ca06e..a91b035 100644
--- a/src/core/src/tonkadur/fate/v1/lang/computation/SetFieldsComputation.java
+++ b/src/core/src/tonkadur/fate/v1/lang/computation/SetFieldsComputation.java
@@ -21,12 +21,7 @@ public class SetFieldsComputation extends Computation
    /***************************************************************************/
    /**** PROTECTED ************************************************************/
    /***************************************************************************/
-
-   /***************************************************************************/
-   /**** PUBLIC ***************************************************************/
-   /***************************************************************************/
-   /**** Constructors *********************************************************/
-   public SetFieldsComputation
+   protected SetFieldsComputation
    (
       final Origin origin,
       final Computation target,
@@ -39,6 +34,52 @@ public class SetFieldsComputation extends Computation
       this.field_assignments = field_assignments;
    }
 
+   /***************************************************************************/
+   /**** PUBLIC ***************************************************************/
+   /***************************************************************************/
+   public static SetFieldsComputation build
+   (
+      final Origin origin,
+      final Computation target,
+      final List<Cons<Origin, Cons<String, Computation>>> field_assignments
+   )
+   {
+      // A bit of a lazy solution: build field references, then extract the data
+      final List<Cons<String, Computation>> assignments;
+
+      target.expect_non_string();
+
+      assignments = new ArrayList<Cons<String, Computation>>();
+
+      for
+      (
+         final Cons<Origin, Cons<String, Computation>> entry: field_assignments
+      )
+      {
+         final FieldAccess fa;
+         final Computation cp;
+
+         fa =
+            FieldAccess.build
+            (
+               entry.get_car(),
+               target,
+               entry.get_cdr().get_car()
+            );
+
+         cp = entry.get_cdr().get_cdr();
+
+         RecurrentChecks.handle_expected_type_propagation(cp, fa.get_type());
+         RecurrentChecks.assert_can_be_used_as(cp, fa.get_type());
+
+         assignments.add(new Cons(fa.get_field_name(), cp));
+      }
+
+      return new SetFieldsComputation(origin, target, assignments);
+   }
+
+   /**** Constructors *********************************************************/
+
    /**** Accessors ************************************************************/
    @Override
    public void get_visited_by (final ComputationVisitor cv)
diff --git a/src/core/src/tonkadur/fate/v1/lang/computation/SwitchValue.java b/src/core/src/tonkadur/fate/v1/lang/computation/SwitchValue.java
index afcdf12..8f7561b 100644
--- a/src/core/src/tonkadur/fate/v1/lang/computation/SwitchValue.java
+++ b/src/core/src/tonkadur/fate/v1/lang/computation/SwitchValue.java
@@ -56,32 +56,77 @@ public class SwitchValue extends Computation
    throws ParsingError
    {
       final Type target_type;
-      final Type first_type;
-      Type candidate_hint, hint;
+      Type candidate_hint;
 
       target_type = target.get_type();
+      target_type.expect_string();
 
-      candidate_hint =  branches.get(0).get_car().get_type();
-      hint = branches.get(0).get_cdr().get_type();
+      candidate_hint = branches.get(0).get_car().get_type();
 
       for (final Cons<Computation, Computation> entry: branches)
       {
+         entry.get_car().expect_string();
+
          candidate_hint =
             RecurrentChecks.assert_can_be_used_as
             (
                entry.get_car(),
                candidate_hint
             );
+      }
+
+      return
+         new SwitchValue
+         (
+            origin,
+            new FutureType(origin),
+            target,
+            branches,
+            default_value
+         );
+   }
+
+   /**** Accessors ************************************************************/
+   @Override
+   public void expect_non_string ()
+   throws ParsingError
+   {
+      Type hint;
+
+      default_value.expect_non_string();
+
+      hint = default_value.get_type();
+
+      for (final Cons<Computation, Computation> entry: branches)
+      {
+         entry.get_cdr().expect_non_string();
 
          hint = RecurrentChecks.assert_can_be_used_as(entry.get_cdr(), hint);
       }
 
-      hint = RecurrentChecks.assert_can_be_used_as(default_value, hint);
+      ((FutureType) get_type()).resolve_to(hint);
+   }
+
+   @Override
+   public void expect_string ()
+   throws ParsingError
+   {
+      Type hint;
+
+      default_value.expect_string();
+
+      hint = default_value.get_type();
 
-      return new SwitchValue(origin, hint, target, branches, default_value);
+      for (final Cons<Computation, Computation> entry: branches)
+      {
+         entry.get_cdr().expect_string();
+
+         hint = RecurrentChecks.assert_can_be_used_as(entry.get_cdr(), hint);
+      }
+
+      ((FutureType) get_type()).resolve_to(hint);
    }
 
-   /**** Accessors ************************************************************/
    @Override
    public void get_visited_by (final ComputationVisitor cv)
    throws Throwable
diff --git a/src/core/src/tonkadur/fate/v1/lang/computation/generic/LambdaEvaluation.java b/src/core/src/tonkadur/fate/v1/lang/computation/generic/LambdaEvaluation.java
index dc5fcb5..0431e11 100644
--- a/src/core/src/tonkadur/fate/v1/lang/computation/generic/LambdaEvaluation.java
+++ b/src/core/src/tonkadur/fate/v1/lang/computation/generic/LambdaEvaluation.java
@@ -105,31 +105,11 @@ public class LambdaEvaluation extends GenericComputation
 
       call_parameters.remove(0);
 
-      /* String vs Variable resolution */
-      try
-      {
-         (new Merge<Type, Computation, Boolean>()
-         {
-            @Override
-            public Boolean risky_lambda (final Type t, final Computation p)
-            throws ParsingError
-            {
-               if (t.can_be_used_as(Type.STRING))
-               {
-                  p.expect_string();
-               }
-               else
-               {
-                  p.expect_non_string();
-               }
-               return Boolean.TRUE;
-            }
-         }).risky_merge(lambda_signature, call_parameters);
-      }
-      catch (final Throwable e)
-      {
-         // Will be handled better in the check below.
-      }
+      RecurrentChecks.propagate_expected_types
+      (
+         call_parameters,
+         lambda_signature
+      );
 
       RecurrentChecks.assert_computations_matches_signature
       (
diff --git a/src/core/src/tonkadur/fate/v1/lang/computation/generic/Operation.java b/src/core/src/tonkadur/fate/v1/lang/computation/generic/Operation.java
index 48cf0a9..e443959 100644
--- a/src/core/src/tonkadur/fate/v1/lang/computation/generic/Operation.java
+++ b/src/core/src/tonkadur/fate/v1/lang/computation/generic/Operation.java
@@ -488,6 +488,11 @@ public class Operation extends GenericComputation
       operator_min_arity = operator.get_minimum_arity();
       operands_size = operands.size();
 
+      for (final Computation c: operands)
+      {
+         c.expect_non_string();
+      }
+
       if
       (
          (operands_size < operator_min_arity)
diff --git a/src/core/src/tonkadur/fate/v1/lang/instruction/Assert.java b/src/core/src/tonkadur/fate/v1/lang/instruction/Assert.java
index 3ec088e..7e06e87 100644
--- a/src/core/src/tonkadur/fate/v1/lang/instruction/Assert.java
+++ b/src/core/src/tonkadur/fate/v1/lang/instruction/Assert.java
@@ -47,6 +47,9 @@ public class Assert extends Instruction
    )
    throws ParsingError
    {
+      condition.expect_non_string();
+      message.expect_string();
+
       RecurrentChecks.assert_can_be_used_as(condition, Type.BOOL);
 
       return new Assert(origin, condition, message);
diff --git a/src/core/src/tonkadur/fate/v1/lang/instruction/CondInstruction.java b/src/core/src/tonkadur/fate/v1/lang/instruction/CondInstruction.java
index b7eb9bb..e179a9d 100644
--- a/src/core/src/tonkadur/fate/v1/lang/instruction/CondInstruction.java
+++ b/src/core/src/tonkadur/fate/v1/lang/instruction/CondInstruction.java
@@ -49,6 +49,7 @@ public class CondInstruction extends Instruction
    {
       for (final Cons<Computation, Instruction> branch: branches)
       {
+         branch.get_car().expect_non_string();
          RecurrentChecks.assert_can_be_used_as(branch.get_car(), Type.BOOL);
       }
 
diff --git a/src/core/src/tonkadur/fate/v1/lang/instruction/Display.java b/src/core/src/tonkadur/fate/v1/lang/instruction/Display.java
index 3d5d7ce..437dbbf 100644
--- a/src/core/src/tonkadur/fate/v1/lang/instruction/Display.java
+++ b/src/core/src/tonkadur/fate/v1/lang/instruction/Display.java
@@ -31,6 +31,8 @@ public class Display extends Instruction
    {
       super(origin);
 
+      content.expect_string();
+
       this.content = content;
    }
 
diff --git a/src/core/src/tonkadur/fate/v1/lang/instruction/DoWhile.java b/src/core/src/tonkadur/fate/v1/lang/instruction/DoWhile.java
index 4fe170f..e34dd94 100644
--- a/src/core/src/tonkadur/fate/v1/lang/instruction/DoWhile.java
+++ b/src/core/src/tonkadur/fate/v1/lang/instruction/DoWhile.java
@@ -49,6 +49,8 @@ public class DoWhile extends Instruction
    )
    throws ParsingError
    {
+      condition.expect_non_string();
+
       RecurrentChecks.assert_can_be_used_as(condition, Type.BOOL);
 
       return new DoWhile(origin, condition, body);
diff --git a/src/core/src/tonkadur/fate/v1/lang/instruction/EventOption.java b/src/core/src/tonkadur/fate/v1/lang/instruction/EventOption.java
index 8cfc0a9..d2d4fc3 100644
--- a/src/core/src/tonkadur/fate/v1/lang/instruction/EventOption.java
+++ b/src/core/src/tonkadur/fate/v1/lang/instruction/EventOption.java
@@ -70,6 +70,12 @@ public class EventOption extends Instruction
    )
    throws ParsingError
    {
+      RecurrentChecks.propagate_expected_types
+      (
+         parameters,
+         event.get_signature()
+      );
+
       RecurrentChecks.assert_computations_matches_signature
       (
          origin,
diff --git a/src/core/src/tonkadur/fate/v1/lang/instruction/ExtraInstructionInstance.java b/src/core/src/tonkadur/fate/v1/lang/instruction/ExtraInstructionInstance.java
index ecfa012..e485ffa 100644
--- a/src/core/src/tonkadur/fate/v1/lang/instruction/ExtraInstructionInstance.java
+++ b/src/core/src/tonkadur/fate/v1/lang/instruction/ExtraInstructionInstance.java
@@ -46,6 +46,12 @@ public class ExtraInstructionInstance extends GenericInstruction
    )
    throws ParsingError
    {
+      RecurrentChecks.propagate_expected_types
+      (
+         parameters,
+         instruction.get_signature()
+      );
+
       RecurrentChecks.assert_computations_matches_signature
       (
          origin,
diff --git a/src/core/src/tonkadur/fate/v1/lang/instruction/For.java b/src/core/src/tonkadur/fate/v1/lang/instruction/For.java
index b6734b2..d17c30b 100644
--- a/src/core/src/tonkadur/fate/v1/lang/instruction/For.java
+++ b/src/core/src/tonkadur/fate/v1/lang/instruction/For.java
@@ -57,6 +57,8 @@ public class For extends Instruction
    )
    throws ParsingError
    {
+      condition.expect_non_string();
+
       RecurrentChecks.assert_can_be_used_as(condition, Type.BOOL);
 
       return new For(origin, condition, pre, body, post);
diff --git a/src/core/src/tonkadur/fate/v1/lang/instruction/ForEach.java b/src/core/src/tonkadur/fate/v1/lang/instruction/ForEach.java
index c3c049b..63188ad 100644
--- a/src/core/src/tonkadur/fate/v1/lang/instruction/ForEach.java
+++ b/src/core/src/tonkadur/fate/v1/lang/instruction/ForEach.java
@@ -39,6 +39,8 @@ public class ForEach extends Instruction
    {
       super(origin);
 
+      collection.expect_non_string();
+
       this.collection = collection;
       this.var_name = var_name;
       this.body = body;
diff --git a/src/core/src/tonkadur/fate/v1/lang/instruction/IfElseInstruction.java b/src/core/src/tonkadur/fate/v1/lang/instruction/IfElseInstruction.java
index 477b227..fef4920 100644
--- a/src/core/src/tonkadur/fate/v1/lang/instruction/IfElseInstruction.java
+++ b/src/core/src/tonkadur/fate/v1/lang/instruction/IfElseInstruction.java
@@ -51,6 +51,8 @@ public class IfElseInstruction extends Instruction
    )
    throws ParsingError
    {
+      condition.expect_non_string();
+
       RecurrentChecks.assert_can_be_used_as(condition, Type.BOOL);
 
       return new IfElseInstruction(origin, condition, if_true, if_false);
diff --git a/src/core/src/tonkadur/fate/v1/lang/instruction/IfInstruction.java b/src/core/src/tonkadur/fate/v1/lang/instruction/IfInstruction.java
index 0f29115..b5a5d96 100644
--- a/src/core/src/tonkadur/fate/v1/lang/instruction/IfInstruction.java
+++ b/src/core/src/tonkadur/fate/v1/lang/instruction/IfInstruction.java
@@ -49,6 +49,8 @@ public class IfInstruction extends Instruction
    )
    throws ParsingError
    {
+      condition.expect_non_string();
+
       RecurrentChecks.assert_can_be_used_as(condition, Type.BOOL);
 
       return new IfInstruction(origin, condition, if_true);
diff --git a/src/core/src/tonkadur/fate/v1/lang/instruction/PromptInteger.java b/src/core/src/tonkadur/fate/v1/lang/instruction/PromptInteger.java
index 9ddf4fb..a869bae 100644
--- a/src/core/src/tonkadur/fate/v1/lang/instruction/PromptInteger.java
+++ b/src/core/src/tonkadur/fate/v1/lang/instruction/PromptInteger.java
@@ -56,6 +56,11 @@ public class PromptInteger extends Instruction
    )
    throws ParsingError
    {
+      target.expect_non_string();
+      min.expect_non_string();
+      max.expect_non_string();
+      label.expect_string();
+
       RecurrentChecks.assert_can_be_used_as(min, Type.INT);
       RecurrentChecks.assert_can_be_used_as(max, Type.INT);
       RecurrentChecks.assert_can_be_used_as(label, Type.TEXT);
diff --git a/src/core/src/tonkadur/fate/v1/lang/instruction/PromptString.java b/src/core/src/tonkadur/fate/v1/lang/instruction/PromptString.java
index 23f1d35..ccb447d 100644
--- a/src/core/src/tonkadur/fate/v1/lang/instruction/PromptString.java
+++ b/src/core/src/tonkadur/fate/v1/lang/instruction/PromptString.java
@@ -56,6 +56,11 @@ public class PromptString extends Instruction
    )
    throws ParsingError
    {
+      target.expect_non_string();
+      min.expect_non_string();
+      max.expect_non_string();
+      label.expect_string();
+
       RecurrentChecks.assert_can_be_used_as(min, Type.INT);
       RecurrentChecks.assert_can_be_used_as(max, Type.INT);
       RecurrentChecks.assert_can_be_used_as(label, Type.TEXT);
diff --git a/src/core/src/tonkadur/fate/v1/lang/instruction/SequenceCall.java b/src/core/src/tonkadur/fate/v1/lang/instruction/SequenceCall.java
index c65f490..40195a4 100644
--- a/src/core/src/tonkadur/fate/v1/lang/instruction/SequenceCall.java
+++ b/src/core/src/tonkadur/fate/v1/lang/instruction/SequenceCall.java
@@ -51,6 +51,23 @@ public class SequenceCall extends Instruction
       return parameters;
    }
 
+   public void perform_signature_checks (final List<Type> signature)
+   throws ParsingError
+   {
+      RecurrentChecks.propagate_expected_types
+      (
+         parameters,
+         signature
+      );
+
+      RecurrentChecks.assert_computations_matches_signature
+      (
+         get_origin(),
+         parameters,
+         signature
+      );
+   }
+
    /**** Misc. ****************************************************************/
    @Override
    public String toString ()
diff --git a/src/core/src/tonkadur/fate/v1/lang/instruction/SequenceJump.java b/src/core/src/tonkadur/fate/v1/lang/instruction/SequenceJump.java
index fb95d84..3df941c 100644
--- a/src/core/src/tonkadur/fate/v1/lang/instruction/SequenceJump.java
+++ b/src/core/src/tonkadur/fate/v1/lang/instruction/SequenceJump.java
@@ -34,6 +34,23 @@ public class SequenceJump extends Instruction
    }
 
    /**** Accessors ************************************************************/
+   public void perform_signature_checks (final List<Type> signature)
+   throws ParsingError
+   {
+      RecurrentChecks.propagate_expected_types
+      (
+         parameters,
+         signature
+      );
+
+      RecurrentChecks.assert_computations_matches_signature
+      (
+         get_origin(),
+         parameters,
+         signature
+      );
+   }
+
    @Override
    public void get_visited_by (final InstructionVisitor iv)
    throws Throwable
diff --git a/src/core/src/tonkadur/fate/v1/lang/instruction/SequenceVariableCall.java b/src/core/src/tonkadur/fate/v1/lang/instruction/SequenceVariableCall.java
index e834aaf..0e4a654 100644
--- a/src/core/src/tonkadur/fate/v1/lang/instruction/SequenceVariableCall.java
+++ b/src/core/src/tonkadur/fate/v1/lang/instruction/SequenceVariableCall.java
@@ -57,6 +57,10 @@ public class SequenceVariableCall extends Instruction
    {
       final List<Type> signature;
 
+      sequence.expect_non_string();
+
+      // TODO: change this system, since we'd rather use the signature to tell
+      // the parameters what to expect.
       ((SequenceType) sequence.get_type()).propose_signature_from_parameters
       (
          parameters
diff --git a/src/core/src/tonkadur/fate/v1/lang/instruction/SequenceVariableJump.java b/src/core/src/tonkadur/fate/v1/lang/instruction/SequenceVariableJump.java
index 483ff95..f0a0cae 100644
--- a/src/core/src/tonkadur/fate/v1/lang/instruction/SequenceVariableJump.java
+++ b/src/core/src/tonkadur/fate/v1/lang/instruction/SequenceVariableJump.java
@@ -57,6 +57,10 @@ public class SequenceVariableJump extends Instruction
    {
       final List<Type> signature;
 
+      sequence.expect_non_string();
+
+      // TODO: change this system, since we'd rather use the signature to tell
+      // the parameters what to expect.
       ((SequenceType) sequence.get_type()).propose_signature_from_parameters
       (
          parameters
diff --git a/src/core/src/tonkadur/fate/v1/lang/instruction/SetFields.java b/src/core/src/tonkadur/fate/v1/lang/instruction/SetFields.java
index fff2a2b..cb66542 100644
--- a/src/core/src/tonkadur/fate/v1/lang/instruction/SetFields.java
+++ b/src/core/src/tonkadur/fate/v1/lang/instruction/SetFields.java
@@ -21,22 +21,62 @@ public class SetFields extends Instruction
    /***************************************************************************/
    /**** PROTECTED ************************************************************/
    /***************************************************************************/
+   protected SetFields
+   (
+      final Origin origin,
+      final Computation target,
+      final List<Cons<String, Computation>> field_assignments
+   )
+   {
+      super(origin);
+
+      this.target = target;
+      this.field_assignments = field_assignments;
+   }
 
    /***************************************************************************/
    /**** PUBLIC ***************************************************************/
    /***************************************************************************/
    /**** Constructors *********************************************************/
-   public SetFields
+   public static SetFieldsComputation build
    (
       final Origin origin,
       final Computation target,
-      final List<Cons<String, Computation>> field_assignments
+      final List<Cons<Origin, Cons<String, Computation>>> field_assignments
    )
    {
-      super(origin);
+      // A bit of a lazy solution: build field references, then extract the data
+      final List<Cons<String, Computation>> assignments;
 
-      this.target = target;
-      this.field_assignments = field_assignments;
+      target.expect_non_string();
+
+      assignments = new ArrayList<Cons<String, Computation>>();
+
+      for
+      (
+         final Cons<Origin, Cons<String, Computation>> entry: field_assignments
+      )
+      {
+         final FieldAccess fa;
+         final Computation cp;
+
+         fa =
+            FieldAccess.build
+            (
+               entry.get_car(),
+               target,
+               entry.get_cdr().get_car()
+            );
+
+         cp = entry.get_cdr().get_cdr();
+
+         RecurrentChecks.handle_expected_type_propagation(cp, fa.get_type());
+         RecurrentChecks.assert_can_be_used_as(cp, fa.get_type());
+
+         assignments.add(new Cons(fa.get_field_name(), cp));
+      }
+
+      return new SetFields(origin, target, assignments);
    }
 
    /**** Accessors ************************************************************/
diff --git a/src/core/src/tonkadur/fate/v1/lang/instruction/SetValue.java b/src/core/src/tonkadur/fate/v1/lang/instruction/SetValue.java
index 672756a..d077c26 100644
--- a/src/core/src/tonkadur/fate/v1/lang/instruction/SetValue.java
+++ b/src/core/src/tonkadur/fate/v1/lang/instruction/SetValue.java
@@ -46,6 +46,8 @@ public class SetValue extends Instruction
    )
    throws ParsingError
    {
+      value_reference.expect_non_string();
+
       RecurrentChecks.assert_can_be_used_as(element, value_reference);
 
       return new SetValue(origin, element, value_reference);
diff --git a/src/core/src/tonkadur/fate/v1/lang/instruction/SwitchInstruction.java b/src/core/src/tonkadur/fate/v1/lang/instruction/SwitchInstruction.java
index 6c0b021..87a0836 100644
--- a/src/core/src/tonkadur/fate/v1/lang/instruction/SwitchInstruction.java
+++ b/src/core/src/tonkadur/fate/v1/lang/instruction/SwitchInstruction.java
@@ -57,11 +57,15 @@ public class SwitchInstruction extends Instruction
    {
       final Type target_type;
 
+      target.expect_string();
+
       target_type = target.get_type();
 
       for (final Cons<Computation, Instruction> branch: branches)
       {
-         RecurrentChecks.assert_can_be_used_as(branch.get_car(), Type.BOOL);
+         branch.get_car().expect_string();
+
+         RecurrentChecks.assert_can_be_used_as(branch.get_car(), target_type);
       }
 
       return
diff --git a/src/core/src/tonkadur/fate/v1/lang/instruction/TextOption.java b/src/core/src/tonkadur/fate/v1/lang/instruction/TextOption.java
index e612a08..f1479d0 100644
--- a/src/core/src/tonkadur/fate/v1/lang/instruction/TextOption.java
+++ b/src/core/src/tonkadur/fate/v1/lang/instruction/TextOption.java
@@ -31,6 +31,8 @@ public class TextOption extends Instruction
    {
       super(origin);
 
+      text.expect_string();
+
       this.text = text;
       this.effects = effects;
    }
diff --git a/src/core/src/tonkadur/fate/v1/lang/instruction/While.java b/src/core/src/tonkadur/fate/v1/lang/instruction/While.java
index b29b496..14e0c1b 100644
--- a/src/core/src/tonkadur/fate/v1/lang/instruction/While.java
+++ b/src/core/src/tonkadur/fate/v1/lang/instruction/While.java
@@ -49,6 +49,8 @@ public class While extends Instruction
    )
    throws ParsingError
    {
+      condition.expect_non_string();
+
       RecurrentChecks.assert_can_be_used_as(condition, Type.BOOL);
 
       return new While(origin, condition, body);
diff --git a/src/core/src/tonkadur/fate/v1/parser/FateParser.g4 b/src/core/src/tonkadur/fate/v1/parser/FateParser.g4
index 8c5a052..ac3023f 100644
--- a/src/core/src/tonkadur/fate/v1/parser/FateParser.g4
+++ b/src/core/src/tonkadur/fate/v1/parser/FateParser.g4
@@ -845,37 +845,6 @@ returns [Instruction result]
 
    | IMP_SET_FIELDS_KW computation WS* field_value_list WS* R_PAREN
    {
-      /*
-       * A bit of a lazy solution: build field references, then extract the data
-       */
-      final List<Cons<String, Computation>> assignments;
-
-      assignments = new ArrayList<Cons<String, Computation>>();
-
-      for
-      (
-         final Cons<Origin, Cons<String, Computation>> entry:
-            ($field_value_list.result)
-      )
-      {
-         final FieldAccess fa;
-         final Computation cp;
-
-         fa =
-            FieldAccess.build
-            (
-               entry.get_car(),
-               ($computation.result),
-               entry.get_cdr().get_car()
-            );
-
-         cp = entry.get_cdr().get_cdr();
-
-         RecurrentChecks.assert_can_be_used_as(cp, fa.get_type());
-
-         assignments.add(new Cons(fa.get_field_name(), cp));
-      }
-
       $result =
          new SetFields
          (
@@ -885,7 +854,7 @@ returns [Instruction result]
                ($IMP_SET_FIELDS_KW.getCharPositionInLine())
             ),
             ($computation.result),
-            assignments
+            ($field_value_list.result)
          );
    }
 
@@ -2062,17 +2031,33 @@ returns [Computation result]
 :
    WORD
    {
-      $result =
-         new AmbiguousWord
-         (
-            PARSER,
-            PARSER.get_origin_at
+      if ($WORD.text.matches("[0-9]+(\.[0-9]+)?"))
+      {
+         return
+            Constant.build
             (
-               ($WORD.getLine()),
-               ($WORD.getCharPositionInLine())
-            ),
-            ($WORD.text)
-         );
+               PARSER.get_origin_at
+               (
+                  ($WORD.getLine()),
+                  ($WORD.getCharPositionInLine())
+               ),
+               ($WORD.text)
+            );
+      }
+      else
+      {
+         $result =
+            new AmbiguousWord
+            (
+               PARSER,
+               PARSER.get_origin_at
+               (
+                  ($WORD.getLine()),
+                  ($WORD.getCharPositionInLine())
+               ),
+               ($WORD.text)
+            );
+      }
    }
 
    | VARIABLE_KW WORD WS* R_PAREN
@@ -2246,37 +2231,6 @@ returns [Computation result]
 
    | SET_FIELDS_KW computation WS* field_value_list WS* R_PAREN
    {
-      /*
-       * A bit of a lazy solution: build field references, then extract the data
-       */
-      final List<Cons<String, Computation>> assignments;
-
-      assignments = new ArrayList<Cons<String, Computation>>();
-
-      for
-      (
-         final Cons<Origin, Cons<String, Computation>> entry:
-            ($field_value_list.result)
-      )
-      {
-         final FieldAccess fa;
-         final Computation cp;
-
-         fa =
-            FieldAccess.build
-            (
-               entry.get_car(),
-               ($computation.result),
-               entry.get_cdr().get_car()
-            );
-
-         cp = entry.get_cdr().get_cdr();
-
-         RecurrentChecks.assert_can_be_used_as(cp, fa.get_type());
-
-         assignments.add(new Cons(fa.get_field_name(), cp));
-      }
-
       $result =
          new SetFieldsComputation
          (
@@ -2286,7 +2240,7 @@ returns [Computation result]
                ($SET_FIELDS_KW.getCharPositionInLine())
             ),
             ($computation.result),
-            assignments
+            ($field_value_list.result)
          );
    }