in the middle of changing those compile-time errors to runtime ones.

compiler.rkt

@@ -531,8 +531,10 @@
             [(Prefix? op-knowledge)
              (error 'impossible)]
             [(Const? op-knowledge)
-	     ;; FIXME: this needs to be a runtime error to preserve Racket's semantics.
+	     (make-instruction-sequence `(,(make-AssignImmediateStatement 'proc op-knowledge)
-             (error 'application "Can't apply constant ~s as a function" (Const-const op-knowledge))]))))
+					  ,(make-PerformStatement
+					    (make-RaiseOperatorApplicationError! (make-Reg 'proc)))))]))))
+
 
 
 (: compile-general-application (App CompileTimeEnvironment Target Linkage -> InstructionSequence))
@@ -829,15 +831,16 @@
    (StaticallyKnownLam App CompileTimeEnvironment Target Linkage 
                        -> InstructionSequence))
 (define (compile-statically-known-lam-application static-knowledge exp cenv target linkage)
-  (unless (arity-matches? (StaticallyKnownLam-arity static-knowledge)
+  (let ([arity-check
+	 (cond [(arity-matches? (StaticallyKnownLam-arity static-knowledge)
 				(length (App-operands exp)))
-	  ;; FIXME: this needs to be turned into a runtime error, not a compile-time error, to preserve
+		empty-instruction-sequence]
-	  ;; Racket semantics.
+	       [else
-    (error 'arity-mismatch "~s expected ~s arguments, but received ~s" 
+		(make-instruction-sequence 
-           (StaticallyKnownLam-name static-knowledge)
+		 `(,(make-PerformStatement
+		     (make-RaiseArityMismatchError! 
 		      (StaticallyKnownLam-arity static-knowledge)
-           (length (App-operands exp))))
+		      (make-Const (length (App-operands exp)))))))])])
-  
     (let* ([extended-cenv 
 	    (extend-compile-time-environment/scratch-space 
 	     cenv 
@@ -865,12 +868,13 @@
 	   empty-instruction-sequence)
        proc-code
        (juggle-operands operand-codes)
+       arity-check
        (compile-procedure-call/statically-known-lam static-knowledge 
 						    cenv
 						    extended-cenv 
 						    (length (App-operands exp))
 						    target
-                                                  linkage))))
+						    linkage)))))
 
 
 (: juggle-operands ((Listof InstructionSequence) -> InstructionSequence))

il-structs.rkt

@@ -325,6 +325,22 @@
 (define-struct: RaiseContextExpectedValuesError! ([expected : Natural])
   #:transparent)
 
+
+;; Raises an exception that says that we're doing a
+;; procedure application, but got sent an incorrect number.
+(define-struct: RaiseArityMismatchError! ([expected : Arity]
+					  [received : OpArg])
+  #:transparent)
+
+
+;; Raises an exception that says that we're doing a
+;; procedure application, but got sent an incorrect number.
+(define-struct: RaiseOperatorApplicationError! ([operator : OpArg])
+  #:transparent)
+
+
+
+
 ;; Changes over the control located at the given argument from the structure in env[1]
 (define-struct: RestoreControl! ([tag : (U DefaultContinuationPromptTag OpArg)]) #:transparent)
 
@@ -351,6 +367,8 @@
                                UnspliceRestFromStack!
                             
                                RaiseContextExpectedValuesError!
+                               RaiseArityMismatchError!
+			       RaiseOperatorApplicationError!
                                
                                RestoreEnvironment!
                                RestoreControl!))