let x = 4 in x+3 end foo.sml:1.5 Error: syntax error: inserting VALThis error message indicates how the parser attempted to "repair" the input (from a file foo.sml), and in this case indicates that the parser thinks that val is needed after the let (at line 1, column 5 of foo.sml).
Syntax errors in expressions typed into the interactive system (instead of taken from files) are not repaired very well, since the parser cannot take advantage of lookahead beyond what you have typed.
If a syntax error is found in a program, then semantic errors will not be reported (and the program will not be executed).
For more detailed discussion of syntax errors generated by the parser, see the explanations of errors [76] through [79] below.
Error: Compiler bug:
indicate that an unexpected situation has been encountered by
the compiler. Example:
Error: Compiler bug: ModuleUtil: getStr: bad entitySuch a message indicates a bug in the compiler, and it should be reported to sml-bugs@research.bell.labs.com, with self-contained code to reproduce the message if possible.
Most such messages will be secondary error messages, meaning that they occur immediately following a normal (i.e. non "Compiler Bug") error message. Secondary errors typically occur when a primary error disrupts the internal state or data structures of the compiler, and the corrupted state then causes further failures. The SML/NJ compiler is pretty good at recovering from errors and failing gracefully, so secondary Compiler Bug errors are rare.
raise keyword should
evaluate to an exception value, i.e. a value of type exn.
In this case, the value has some other, inappropriate type. E.g.:
raise 3;
stdIn:16.7 Error: argument of raise is not an exception [literal]
raised: int
in expression:
raise 3
datatype 'a T = A of 'a; datatype 'a T = A of 'a datatype 'a T1 = datatype T; stdIn:18.1-18.28 Error: argument type variables in datatype replication datatype T1 = datatype T; datatype 'a T = A of 'a
fun declaration, or one of the
formal parameters of an infix function symbol is missing.
fun f = 3; stdIn:1.5 Error: can't find function arguments in clause infix 3 ++; infix 3 ++ fun (x xx) = 3; stdIn:1.5-2.6 Error: can't find function arguments in clause stdIn:1.5-2.6 Error: illegal function symbol in clause
case
keyword. It's type must agree with the type of the lhs patterns in
the rules (pat => exp) following the
of keyword. All the patterns of the rules also have
to agree in type, but that is another error.
case 3
of true => 1
| false => 2;
stdIn:1.1-25.16 Error: case object and rules don't agree [literal]
rule domain: bool
object: int
in expression:
(case 3
of true => 1
| false => 2)
fun definition, the function name must appear in
each clause. If it is omitted from one or more clauses, this error results.
fun f nil = 1
| (x::y) = x;
stdIn:1.5-17.15 Error: clauses don't all have function name
This error is also reported when the function name in two
clauses of the function definition differ, for instance because
of a misspelling.
fun test (SOME s) = true
| teat (NONE) = false;
stdIn:120.5-121.24 Error: clauses don't all have function name
fun declaration, each clause, or rule, separated by
| (vertical bar symbol), has to have the same number of
curried arguments.
fun f x y = 3
| f a b c = 4;
stdIn:1.5-26.16 Error: clauses don't all have same number of patterns
stdIn:24.6-26.16 Error: types of rules don't agree [tycon mismatch]
earlier rule(s): 'Z * 'Y -> int
this rule: 'X * 'W * 'V -> int
in rule:
(a,b,c) => 4
nil can't be applied to an
argument in a pattern.
val nil x = []; stdIn:1.5-24.8 Error: constant constructor applied to argument in pattern:nil
datatype t = A of int;
val A true = A 3;
stdIn:1.1-26.3 Error: constructor and argument don't agree in pattern [tycon mismatch]
constructor: int -> t
argument: bool
in pattern:
A true
datatype t = A of int val A = A 3; stdIn:17.5-17.12 Error: data constructor A used without argument in pattern
signature S =
sig
datatype t = A of int
end;
signature S = sig datatype t = A of int end
structure A : S =
struct
datatype t = A of int | B
end;
stdIn:1.1-27.4 Error: datatype t does not match specification
constructors in actual only: B
datatype t = A | B | A of int; stdIn:1.1-26.5 Error: datatype t has duplicate constructor name(s): A
signature S =
sig
type u
datatype s = A of u
sharing type u = s
end;
stdIn:16.1-21.4 Error: dependency cycle in instantiate
By default, every signature is instantiated when it is declared, to
detect errors as early as possible. However, signature instantiation
is strictly only necessary when a signature is used as a functor
parameter signature or in an opaque (:>) signature constraint.
signature S =
sig
datatype t = A of int
end;
signature S = sig datatype t = A of int end
signature T =
sig
datatype u = A
include S
end;
stdIn:27.3-28.13 Error: duplicate constructor specifications for A caused by include
exception E of int and E of bool; stdIn:17.1-18.14 Error: duplicate exception declaration: ENote that it is ok if the same exception name is declared in different exception declarations, as in the following.
exception E of int; exception E of int exception E of bool; exception E of bool
val rec
declaration, the names of the functions must be distinct.
val rec f = (fn x => x) and f = (fn y => y + 3); stdIn:21.1-22.24 Error: duplicate function name in val rec dec: f
fun
declaration, the names of the functions must be distinct.
fun f x = x and f y = y + 3; stdIn:1.1-23.16 Error: duplicate function names in fun dec: f
{a=3,b=true,a="abc"};
stdIn:1.1-1.21 Error: duplicate label in record: a
fun f {a=x,a=y} = 3;
stdIn:2.2-2.11 Error: duplicate label in record: a
x cannot be specified
twice as a value or constructor, but it can be specified as a
value, as a type, as a structure, and as a functor in the same
signature.
signature S =
sig
val x : int
val x : bool
end;
stdIn:20.3-21.16 Error: duplicate specifications for variable or constructor x in signature
signature S =
sig
type t
type t
end;
stdIn:24.3-25.10 Error: duplicate specifications for type constructor t in signature
signature S =
sig
exception Foo
exception Foo of int
end;
stdIn:28.3-29.24 Error: duplicate specifications for variable or constructor Foo in signature
signature S =
sig
structure A : sig end
structure A : sig end
end;
stdIn:32.3-33.25 Error: duplicate specifications for structure A in signature
signature S =
sig
val x : int
datatype t = x
end;
stdIn:36.3-37.18 Error: duplicate specifications for variable or constructor x in signature
signature S =
sig
val x : int
type x
structure x : sig end
end;
signature S =
sig
val x : int
type x
structure x : sig end
end
include spec. If the
included functor spec comes first, you get error [19] instead.
signature S1 =
sig
functor F () : sig end
end;
signature S1 = sig functor F : (: ) : end
signature S2 =
sig
include S1
functor F(X: sig val x : int end): sig end
end;
stdIn:55.3-56.46 Error: duplicate specifications for functor F in signature
signature S2 =
sig
functor F(X: sig val x : int end): sig end
include S1
end;
stdIn:59.3-60.14 Error: duplicate specifications for functor F caused by include
include spec. If the
included structure spec comes first, you get error [19] instead.
signature S1 =
sig
structure A : sig end
end;
signature S1 = sig structure A : sig end end
signature S2 =
sig
structure A : sig val x : int end
include S1
end;
stdIn:67.3-68.14 Error: duplicate specifications for structure A caused by include
signature S3 =
sig
include S1
structure A : sig val x : int end
end;
stdIn:71.3-72.37 Error: duplicate specifications for structure A in signature
include spec. If the
included structure spec comes first, you get error [19] instead.
signature S1 =
sig
type t
end;
signature S1 = sig type t end
signature S2 =
sig
type 'a t
include S1
end;
stdIn:79.3-80.14 Error: duplicate specifications for type t caused by include
signature S3 =
sig
include S1
type 'a t
end;
stdIn:83.3-84.13 Error: duplicate specifications for type constructor t in signature
and.
If the simultaneous declaration is split into
separate declarations, there is no error.
type t = int and t = bool; stdIn:17.1-18.13 Error: duplicate type definition: t type t = int; type t = int type t = bool; type t = bool
withtype part.
datatype t = A and t = B; stdIn:1.1-19.10 Error: duplicate type names in type declaration: t datatype t = A withtype t = int; stdIn:1.1-20.17 Error: duplicate type names in type declaration: t
type ('a,'a) t = 'a * 'a;
stdIn:21.4-21.11 Error: duplicate type variable name: a
datatype ('a,'a) t = A of 'a;
stdIn:1.1-21.15 Error: duplicate type variable name: a
fun ('a,'a) f(x:'a) = x;
stdIn:1.1-21.10 Error: duplicate type variable name: a
include spec. If the
included structure spec comes first, you get error [19] instead. It
does not matter whether the multiple value specifications give the
same type or not.
signature S1 =
sig
val x : int
end;
signature S1 = sig val x : int end
signature S2 =
sig
val x : bool
include S1
end;
stdIn:29.3-30.14 Error: duplicate value specifications for x caused by include
signature S3 =
sig
val x : int
include S1
end;
stdIn:33.3-34.14 Error: duplicate value specifications for x caused by include
signature S4 =
sig
include S1
val x : int
end;
stdIn:37.3-38.15 Error: duplicate specifications for variable or constructor x in signature
fun f(x,x) = x; stdIn:1.5-2.10 Error: duplicate variable in pattern(s): x fun f x x = x; stdIn:1.5-2.9 Error: duplicate variable in pattern(s): x val (x,x) = (3,3); stdIn:1.1-36.3 Error: duplicate variable in pattern(s): x
val x : 'a list = (fn x => x) nil; stdIn:1.1-37.14 Error: explicit type variable cannot be generalized at its binding declaration: 'a val 'a (x: 'a list) = (fn x => x) nil; stdIn:1.1-38.5 Error: explicit type variable cannot be generalized at its binding declaration: 'a
fun f x = (hd x)+1 handle Empty => true;
stdIn:2.6-38.7 Error: expression and handler don't agree [literal]
body: int
handler range: bool
in expression:
hd x + 1
handle
Empty => true
| exn => raise exn
op keyword.
+(2,3); stdIn:1.1 Error: expression or pattern begins with infix identifier "+" op +(2,3); val it = 5 : int
op keyword.
2 +;
stdIn:40.4 Error: expression or pattern ends with infix identifier "+"
stdIn:40.1-40.4 Error: operator is not a function [literal]
operator: int
in expression:
2 +
(fn x => x) +;
stdIn:40.3 Error: expression or pattern ends with infix identifier "+"
(fn x => x) op +;
val it = fn : int * int -> int
infix 10 ++; stdIn:43.7-43.9 Error: fixity precedence must be between 0 and 9 infix ~2 ++; stdIn:2.2-2.4 Error: fixity precedence must be between 0 and 9
exception Foo = nil; stdIn:17.1-17.20 Error: found data constructor instead of exception
val x = 3; val x = 3 : int exception Foo = x; stdIn:18.1-18.18 Error: found variable instead of exception
handler
keyword, the type of the patterns on the left hand side the rule
must be exn. In the example below, the first error
message is caused by a mismatch with an implicit default rule that
handles exceptions not handled by the explicit rules of the handler.
3 handle nil => 4;
stdIn:1.1-18.7 Error: types of rules don't agree [tycon mismatch]
earlier rule(s): 'Z list -> int
this rule: exn -> 'Y
in rule:
exn => raise exn
stdIn:1.1-18.7 Error: handler domain is not exn [tycon mismatch]
handler domain: 'Z list
in expression:
3
handle
nil => 4
| exn => raise exn
signature S =
sig
datatype 'a t = datatype bool
end;
stdIn:26.3-26.33 Error: ill-formed datatype spec
as
keyword can have a type constraint, but only one. This error also
occurs in other circumstances, as illustrated by the second example.
val x : int list : int list as y::z = [1,2]; stdIn:29.5-29.36 Error: illegal (multiple?) type constraints in AS pattern val (x: int list) as (y::z : int list) = [1]; stdIn:1.5-24.10 Error: illegal (multiple?) type constraints in AS pattern stdIn:1.5-24.10 Error: parentheses illegal around variable in AS pattern val x : int list as (y::z) = [1,2]; stdIn:1.1-24.6 Warning: binding not exhaustive x as y :: z = ... val x = [1,2] : int list val y = 1 : int val z = [2] : int list
fun and the equal sign
must be a well-formed applicative term, and the operator (i.e. the function
part of the top-level application) of this term must be a simple
identifier. If the application has an infix operator, it must
be parenthesized (unless followed immediately by a type constraint
or the equal sign); otherwise it may not be parenthesized.
fun (f x) = 3; (* bad parentheses *) stdIn:1.5-2.5 Error: can't find function arguments in clause stdIn:1.5-2.5 Error: illegal function symbol in clause fun (x+y) = 3; (* ok; redefines infix + operator *) val + = fn : 'a * 'b -> int
signature XSIG = sig
datatype ('a, 'b) t = A of 'a | B of 'b
end
functor F
(type u
structure X: XSIG
sharing type X.t = u) =
struct
end
stdIn:49.11-54.6 Error: inconsistent arities in type sharing t = u : t
has arity 2 and u has arity 0.
signature S =
sig
eqtype t
datatype u = U of int -> int (* not an equality type *)
sharing type t = u
end;
stdIn:17.1-22.4 Error: inconsistent equality properties in type sharing
infix foo; infix foo fun foo (x,y) = x + y; stdIn:34.5-34.8 Error: infix operator "foo" used without "op" in fun decThe correct definition is:
fun op foo(x,y) = x +y; val foo = fn : int * int -> int
fun in
a function declaration is a parenthesized application, implying an
infix application, but the middle subterm is not an infix symbol.
fun (x f y) = (); (* would work if "f" were infix *) stdIn:18.8 Error: infix operator required, or delete parentheses fun x f y = (); (* ok, but maybe not what was intended *) val x = fn : 'a -> 'b -> unit
val rec declaration, the if the
identifier being declared (on the left hand side of the declaration) is
an infix symbol, it must be preceeded by the op
keyword.
infix ++; infix ++ val rec ++ = (fn x => x); stdIn:17.9-17.11 Error: infix symbol "++" used where a nonfix identifier was expected val rec op ++ = (fn x => x); val ++ = fn : 'a -> 'a
Compiler.PPTable.install_pp installs a
user-defined pretty printer function (the second argument) for a
generative (i.e. datatype or abstype) designated by the first
argument, which must be a nonempty list of strings that can be
interpreted as a symbolic path (longTyCon) naming a
datatype or abstract type in the current environment.
This function should only be called at top level.
Compiler.PPTable.install_pp [] (fn x => fn y => ()); Error: install_pp: empty path
Compiler.PPTable.install_pp installs a
user-defined pretty printer function (the second argument) for a
generative (i.e. datatype or abstype) designated by the first
argument, which must be a nonempty list of strings that can be
interpreted as a symbolic path (longTyCon) naming a datatype
or abstype in the current environment. This function should only
be called at top level.
Compiler.PPTable.install_pp ["t"] (fn x => fn y => ()); Error: install_pp: nongenerative type constructor
Option.valOf(Int.minInt) to Option.valOf(Int.maxInt)
val x = 1073741823; val x = 1073741823 : int val x = 1073741824; stdIn:2.4-22.7 Error: int constant too large val x = ~1073741824; val x = ~1073741824 : int val x = ~1073741825; stdIn:30.10-30.21 Error: int constant too large
Compiler.Control.MC.matchNonExhaustiveError
is set to true (the default is false), otherwise it is a warning if
Compiler.Control.MC.matchNonExhaustiveWarn
is set to true. If neither of these flags is true, then
the compiler does not complain about nonexhaustive matches.
fun f 0 = 1
| f 1 = 1;
stdIn:1.1-22.12 Error: match nonexhaustive
0 => ...
1 => ...
val f = fn : int -> int
Compiler.Control.MC.matchRedundantError
is set to false (default is true), only a warning message
is given. If
Compiler.Control.MC.matchRedundantWarn
is also false (default is true), no message is generated.
fun f (0, true) = 1
| f (0, false) = 2
| f (0, _) = 3
| f _ = 4;
stdIn:24.1-27.14 Error: match redundant
(0,true) => ...
(0,false) => ...
--> (0,_) => ...
_ => ...
Compiler.Control.MC.matchNonExhaustiveError
Compiler.Control.MC.matchNonExhaustiveWarn
Compiler.Control.MC.matchRedundantError
Compiler.Control.MC.matchRedundantWarn
Example:
fun f 1 = 1
| f 2 = 3
| f 1 = 4 ;
stdIn:1.1-24.12 Error: match redundant and nonexhaustive
1 => ...
2 => ...
--> 1 => ...
signature S = sig
type t
end
where type t = int
and type t = bool;
stdIn:1.1-72.20 Error: multiple where defs for t
or even:
signature S = sig
type t
end
where type t = int
and type t = int;
stdIn:1.1-76.19 Error: multiple where defs for t
fun f (0 0) = true; stdIn:17.5-17.19 Error: non-constructor applied to argument in pattern
val a = 0; val a = 0 : int fun f (a 0) = true; stdIn:18.5-18.19 Error: non-constructor applied to argument in pattern: a
signature S = sig
structure A : sig end
sharing A = B.C
end;
stdIn:41.11-41.18 Error: nonlocal path in structure sharing: B.C
signature S = sig
type t
sharing type t = B.t
end;
stdIn:44.16-44.23 Error: nonlocal path in type sharing: B.t
fun f true = 0
| f false = 1;
val f = fn : bool -> int
f 3;
stdIn:25.1-25.4 Error: operator and operand don't agree [literal]
operator domain: bool
operand: int
in expression:
f 3
3 true;
stdIn:1.1-19.6 Error: operator is not a function [literal]
operator: int
in expression:
3 true
|), the type
of all the subpatterns must agree.
fun f (0 | 1 | true) = 0;
stdIn:1.1-21.4 Error: or-patterns don't agree [literal]
expected: int
found: bool
in pattern:
(1 | true)
fun f 0w100000000000 = 0
| f _ = 1;
stdIn:1.1-27.12 Error: out-of-range word literal in pattern: 0w100000000000
true + true;
stdIn:19.5 Error: overloaded variable not defined at type
symbol: +
type: bool
fun declaration, each clause, or rule, separated by
| (vertical bar symbol), has to have the same type (both
in the type accepted by the clauses, and the type returned by the clauses).
datatype typeA = A;
datatype typeA = A
datatype typeB = B;
datatype typeB = B
fun f A = 0
| f B = 0;
stdIn:36.1-37.12 Error: parameter or result constraints of clauses don't agree [tycon mismatch]
this clause: typeB -> 'Z
previous clauses: typeA -> 'Z
in declaration:
f =
(fn A => 0
| B => 0)
pat as pat, where the pattern to the left
of the "as" is a simple variable, the variable must not be wrapped in parentheses.
val ((a) as (b,c)) = (4,5); stdIn:19.5-31.2 Error: parentheses illegal around variable in AS pattern
fun f (0:bool)=0;
stdIn:38.1-38.17 Error: pattern and constraint don't agree [literal]
pattern: int
constraint: bool
in pattern:
0 : bool
val pat = exp, the type of
pat must match the type of exp.
val s:string = 6;
stdIn:1.1-18.6 Error: pattern and expression in val dec don't agree [literal]
pattern: string
expression: int
in declaration:
s : string = 6
val pat = exp, the type of
pat must match the type of exp.
val s:string = 6;
stdIn:1.1-18.6 Error: pattern and expression in val dec don't agree [literal]
pattern: string
expression: int
in declaration:
s : string = 6
pat as pat, the first pattern
must be a simple variable, not a more complex pattern using tuples
or data constructors.
val (a,_) as (_,b) = (7,5); stdIn:1.5-18.8 Error: pattern to left of AS must be variable
val (a,_) as (_,b) = (7,5); stdIn:1.5-18.8 Error: pattern to left of AS must be variable
signature SIG =
sig
structure A : sig end
structure B : sig structure Z : sig end
end where Z = A
structure C : sig structure Z : sig end
end where Z = A
sharing B = C
end;
stdIn:1.1-38.4 Error: possibly inconsistent structure definitions at: B.Z
2e309;
uncaught exception BadReal
raised at: bignums/realconst.sml:228.54-228.63
At present, a bug in the compiler raises an exception instead of
printing the appropriate error message.
fun nil x = x; stdIn:1.5-2.9 Error: rebinding data constructor "nil" as variable
4 handle Match => 5 | e => 6 | Bind => 7;
stdIn:1.1-20.15 Error: redundant patterns in match
Match => ...
e => ...
--> Bind => ...
signature S1 =
sig
structure A : sig type t end
end
where A=Int and A=Real;
stdIn:32.1-36.23 Error: redundant where definitions
datatype id1 = datatype id2that binds the name id1 to the existing datatype id2, requires that id2 must be a datatype, and not an ordinary type.
datatype myint = datatype int; stdIn:38.1-38.30 Error: rhs of datatype replication not a datatype
datatype id1 = datatype id2that binds the name
id1 to the existing datatype
id2, requires that id2 must be
a datatype, and not an ordinary type.
signature S = sig type t
datatype d = datatype t
end;
stdIn:37.18-40.17 Error: rhs of datatype replication spec not a datatype
fun f(x) : int = "hello";
stdIn:1.1-37.24 Error: right-hand-side of clause doesn't agree with function result type [tycon mismatch]
expression: string
result type: int
in declaration:
f = (fn x => "hello": int)
signature S = sig structure A : sig structure B : sig end end
sharing A = A.B
end;
stdIn:1.1-44.20 Error: Sharing structure with a descendent substructure
functor F()() = struct end; functor F :structure S = F(); stdIn:45.15-45.18 Error: structure S defined by partially applied functor
x andalso val y orelse z; stdIn:1.6 Error: syntax error found at VALNote: Error correction in the parser relies on lookahead. Different amounts of lookahead are used depending on whether input is taken from the interactive toplevel or from a source file. Therefore, error messages for the same program can vary depending on circumstances. (See also the note on error [78].)
For example, let's assume that file delete.sml contains the following code:
structure 99 X =
struct
val x = 1
end
Compiling this file produces:
- use "delete.sml"; [opening delete.sml] delete.sml:1.11-1.13 Error: syntax error: deleting INTNote: Error correction in the parser relies on lookahead. Different amounts of lookahead are used depending on whether input is taken from the interactive toplevel or from a source file. Therefore, error messages for the same program can vary depending on circumstances. (See also the note on error [78].)
For example, let's assume that file insert.sml contains the following code:
let
val x = 1; y = x + x
in
x * y
end
Compiling this file produces:
- use "insert.sml"; [opening insert.sml] insert.sml:2.16 Error: syntax error: inserting VALNote: Error correction in the parser relies on lookahead. Since the interactive parser cannot use lookahead, it is likely that its syntax error messages differ from those that are generated when compiling files. For example, typing the contents of insert.sml directly into the interactive toplevel produces:
let
val x = 1; y = x + x
in
x * y
end;
stdIn:2.14-2.19 Error: syntax error: deleting ID EQUALOP ID
stdIn:2.20-3.3 Error: syntax error: deleting ID ID IN
stdIn:4.3-4.8 Error: syntax error: deleting ID ASTERISK ID
For example, let's assume that file replace.sml contains the following code:
fn x = xCompiling this file produces:
- use "replace.sml"; [opening replace.sml] replace.sml:1.6 Error: syntax error: replacing EQUALOP with DARROWNote: Error correction in the parser relies on lookahead. Different amounts of lookahead are used depending on whether input is taken from the interactive toplevel or from a source file. Therefore, error messages for the same program can vary depending on circumstances. (See also the note on error [78].)
Example:
signature S = sig type ('a, 'b) t end;
signature S = sig type ('a,'b) t end
structure S : S = struct
type 'a t = 'a list
end;
stdIn:75.1-77.4 Error: tycon arity for t does not match specified arity
Example:
signature S = sig datatype t = A | B end; signature S = sig datatype t = A | B end structure S : S = struct type t = int end; stdIn:80.1-82.4 Error: type t must be a datatype stdIn:80.1-82.4 Error: unmatched constructor specification: A stdIn:80.1-82.4 Error: unmatched constructor specification: B
Example:
signature S = sig eqtype t end;
signature S = sig eqtype t end
structure S : S = struct
type t = int -> int
end;
stdIn:86.1-88.4 Error: type t must be an equality type
Example:
val rec f : int = fn x => x;
stdIn:1.1-79.26 Error: type constraint of val rec dec is not a function type [tycon mismatch]
constraint: int
in declaration:
f = (fn x => x)
val rec id : ty1 = exp : ty2and the types
ty1 and ty2 disagree.
val rec f : int -> int = (fn x => x) : bool -> bool;
stdIn:1.1-29.30 Error: type constraints on val rec declaraction disagree [tycon mismatch]
this constraint: bool -> bool
outer constraints: int -> int
in declaration:
f = (fn x => x): bool -> bool
Example:
type ('a, 'b) t = 'a * 'b;
type ('a,'b) t = 'a * 'b
type u = (int, bool, real) t;
stdIn:103.28 Error: type constructor t given 3 arguments, wants 2
Example:
fun f (x: 'a, y: ''a) = (x, y); stdIn:118.2-119.12 Error: type variable a occurs with different equality properties in the same scopeBut:
fun 'a f (x: 'a) = let
fun ''a g (y: ''a) = y = y
in x end;
val f = fn : 'a -> 'a
Example:
signature S = sig
exception E of 'a list
end;
stdIn:135.3-135.26 Error: type variable in exception spec: E
Example:
exception E of 'a list; stdIn:1.1-135.4 Error: type variable in top level exception type
case- and in
fn-expressions.
Examples:
fn true => false
| false => 1;
stdIn:144.1-144.30 Error: types of rules don't agree [literal]
earlier rule(s): bool -> bool
this rule: bool -> int
in rule:
false => 1
fn x =>
case x
of true => false
| false => 1;
stdIn:144.6-144.42 Error: types of rules don't agree [literal]
earlier rule(s): bool -> bool
this rule: bool -> int
in rule:
false => 1
Example:
signature S = sig
functor F: FS
end;
stdIn:145.3-145.17 Error: unbound functor signature: FS
Example:
structure S = F (); stdIn:147.15-147.19 Error: unbound functor: F
Example:
structure A = struct end; structure A : sig end signature S = sig end; signature S = sig end signature S' = S where B = A; stdIn:158.1-158.29 Error: unbound left hand side in where (structure): BBut:
signature S = sig structure B : sig end end; signature S = sig structure B : sig end end signature S' = S where B = A; signature S' = sig structure B : sig end end
where type specification refers to a type inside a
signature that was not declared there.
Example:
type t = int; type t = int signature S = sig end; signature S = sig end signature S' = S where type u = t; stdIn:169.1-169.34 Error: unbound left hand side in where type: uBut:
signature S = sig type u end; signature S = sig type u end signature S' = S where type u = t; signature S' = sig type u = t end
S in the following example:
structure A : S = struct end; stdIn:16.15 Error: unbound signature: S
B in the following example:
- structure A = B; stdIn:2.10 Error: unbound structure: B
t in the following example:
val x : t = (); stdIn:2.4 Error: unbound type constructor: t
type t = 'a list; stdIn:2.5-2.12 Error: unbound type variable in type declaration: 'a datatype 'a t = A of 'b; stdIn:1.1-18.2 Error: unbound type variable in type declaration: 'b
x; stdIn:1.1 Error: unbound variable or constructor: x fun f x = x+y; stdIn:2.8 Error: unbound variable or constructor: y
...)
is used, the context must provide enough type information to determine
what all the fields are (though not necessarily their types).
fun f {x,...} = x;
stdIn:37.1-37.18 Error: unresolved flex record
(can't tell what fields there are besides #x)
fun f ({x,...} : {x: int, y:bool}) = x;
val f = fn : {x:int, y:bool} -> int
If more than one field occurs in the flexible record pattern, then
a different variant of this error message is generated. See error [100].
fun f {x,y,...} = (x,y);
stdIn:118.1-118.24 Error: unresolved flex record (need to know the names of ALL the fields
in this context)
type: {x:'Y, y:'X; 'Z}
signature S =
sig
val x : int
end;
signature S = sig val x : int end
structure A : S =
struct
val x = true
end;
stdIn:21.1-24.4 Error: value type in structure doesn't match signature spec
name: x
spec: int
actual: bool
| symbol. The
component patterns of an or-pattern are required to have exactly the
same variables with the same types.
fun f(nil | x::_) = 1; stdIn:1.5-2.18 Error: variable x does not occur in all branches of or-patternHere the component patterns are
nil and
x::_, and the variable x doesn't
occur in the first pattern.
fun f(Int.+) = 3; stdIn:1.5-2.12 Error: variable found where constructor is required: Int.+
#[exp1,exp2,...],
all the vector element expressions must be of the same type.
#[1,true]; stdIn:1.1-2.5 Error: vector expression type failure [literal] fun f(x:int) = #[x,true]; stdIn:2.11-2.20 Error: vector expression type failure [tycon mismatch]
#[pat1,pat2,...],
all the vector element patterns must be of the same type.
fun f(#[x:int,y:bool]) = (x + 1; not y); stdIn:1.1-2.35 Error: vector pattern type failure [tycon mismatch]
where clause).
structure A = struct end;
structure A : sig end
signature S =
sig
structure X : sig end = A
end
where X = A;
stdIn:27.1-31.12 Error: where defn applied to definitional spec
where type
definition must agree with the arity in type specification that
it applies to.
signature S =
sig
type 'a t
end
where type t = int;
stdIn:1.1-26.19 Error: where type definition has wrong arity: t
where type clause).
signature S =
sig
type t = int
end
where type t = int;
stdIn:1.1-22.19 Error: where type defn applied to definitional spec: t
withtype clause to a
datatype replication declaration or specification.
datatype t = A; datatype t = A datatype s = datatype t withtype u = s list; stdIn:37.1-38.20 Error: withtype not allowed in datatype replication
0w2147483648 (0wx80000000). Similarly
for word literals of type Word32.word (bound 0w4294967296)
and Word8.word (bound 0w256).
0w2147483648; stdIn:1.1-18.3 Error: word constant too large 0wx80000000; stdIn:1.1-18.2 Error: word constant too large 0w4294967296 : Word32.word; stdIn:25.1-25.13 Error: word constant too large 0wx100000000 : Word32.word; stdIn:23.1-23.13 Error: word constant too large 0w256: Word8.word; stdIn:1.1-1.6 Error: word constant too large 0wx100 : Word8.word; stdIn:1.1-24.2 Error: word constant too large
Compiler.Control.MC.matchNonExhaustiveError
is set to false (the default),
Compiler.Control.MC.matchNonExhaustiveWarn
is set to true. If neither of these flags is true, then
the compiler does not complain about nonexhaustive matches.
fun f 0 = 1
| f 1 = 1;
stdIn:1.1-22.12 Warning: match nonexhaustive
0 => ...
1 => ...
val f = fn : int -> int
Compiler.Control.MC.matchRedundantError
is set to false (default is true) and
Compiler.Control.MC.matchRedundantWarn
is true (the default).
fun f (0, true) = 1
| f (0, false) = 2
| f (0, _) = 3
| f _ = 4;
stdIn:24.1-27.14 Warning: match redundant
(0,true) => ...
(0,false) => ...
--> (0,_) => ...
_ => ...
Compiler.Control.MC.matchNonExhaustiveError
Compiler.Control.MC.matchNonExhaustiveWarn
Compiler.Control.MC.matchRedundantError
Compiler.Control.MC.matchRedundantWarn
If the first two are set to false and the latter
two are set to true, then this warning is generated.
fun f 1 = 1
| f 2 = 3
| f 1 = 4 ;
stdIn:1.1-24.12 Warning: match redundant and nonexhaustive
1 => ...
2 => ...
--> 1 => ...
aexp id1 aexp id2 aexpinvolves two infix operators
id1 and
id2 of the same precedence but opposite
associativity, the SML '97 Definition states that the expression is illegal.
But SML/NJ only issues this warning message and associates the
two operators to the left.
- infix 4 <<; infix 4 << - infixr 4 >>; infixr 4 >> - fun (x>>y) = "right"; val >> = fn : 'a * 'b -> string - fun (x<<y) = "left"; val << = fn : 'a * 'b -> string - 1 << 2 >> 3; stdIn:21.8-21.10 Warning: mixed left- and right-associative operators of same precedence val it = "right" : string - 1 >> 2 << 3; stdIn:22.8-22.10 Warning: mixed left- and right-associative operators of same precedence val it = "left" : string
val x = (fn x => x) nil;
stdIn:17.1-17.24 Warning: type vars not generalized because of
value restriction are instantiated to dummy types (X1,X2,...)
val x = [] : ?.X1 list
In this example, the right hand side of the declaration of x
has type 'X list, where 'X is a free type
variable. This type variable cannot be generalized to form a
polymorphic type for x because the right hand expression
is expansive (a function call in this case). So the compiler
eliminates the free type variable 'X be inventing a new
dummy type named X1 and instantiates 'X to
X1. Since X1 won't match any other type,
there is little one can do with x now (one could take
its lenght (0), but one cannot cons any values onto x).