add range constraint type

compiler/types/types.odin

@@ -42,6 +42,7 @@ C_LONGDOUBLE :: Type(28)
 
 BOOL :: Type(29)
 FLOAT :: Type(30)
+RANGE :: Type(31)
 
 DYNAMIC_START :: Type(64)
 
@@ -57,6 +58,7 @@ Kind :: enum u8 {
 	Void,
 	Int_Constraint,
 	Float_Constraint,
+	Range_Constraint,
 	Scalar,
 	Array,
 	Pointer,
@@ -299,6 +301,8 @@ kind :: proc(value: Type, store: ^Store = nil) -> Kind {
 		return .Int_Constraint
 	case FLOAT:
 		return .Float_Constraint
+	case RANGE:
+		return .Range_Constraint
 	case BOOL:
 		return .Scalar
 	}
@@ -338,15 +342,17 @@ is_bool :: proc(value: Type) -> bool {
 }
 
 is_constraint :: proc(value: Type) -> bool {
-	return value == INT || value == FLOAT
+	return value == INT || value == FLOAT || value == RANGE
 }
 
-// constraint_target reports the concrete type a constraint binding takes for an
-// inferred value, or INVALID if the value's numeric family is incompatible.
-// FLOAT accepts integers by defaulting them to f64: a constant integer becomes a
-// float literal in build_constant_expr, while a runtime integer then fails the
-// cross-family f64 coercion in coerce_expr (the intended mismatch error).
-constraint_target :: proc(constraint, inferred: Type) -> Type {
+// constraint_target reports the concrete type a constraint binding (local, or a
+// param/result monomorphized per call site) takes for an inferred value, or
+// INVALID if the value's family is incompatible. FLOAT accepts integers by
+// defaulting them to f64: a constant integer becomes a float literal in
+// build_constant_expr, while a runtime integer then fails the cross-family f64
+// coercion in coerce_expr (the intended mismatch error). RANGE accepts any range
+// type, keeping its inferred element type.
+constraint_target :: proc(constraint, inferred: Type, store: ^Store = nil) -> Type {
 	switch constraint {
 	case INT:
 		return inferred if is_concrete_integer(inferred) else INVALID
@@ -355,18 +361,22 @@ constraint_target :: proc(constraint, inferred: Type) -> Type {
 			return inferred
 		}
 		return F64 if is_concrete_integer(inferred) else INVALID
+	case RANGE:
+		return inferred if is_range(inferred, store) else INVALID
 	}
 	return INVALID
 }
 
-// constraint_accepts reports strict numeric-family membership, used when widening
-// a constraint binding across assignments (no integer-to-float defaulting here).
-constraint_accepts :: proc(constraint, concrete: Type) -> bool {
+// constraint_accepts reports strict family membership, used when widening a
+// constraint binding across assignments (no integer-to-float defaulting here).
+constraint_accepts :: proc(constraint, concrete: Type, store: ^Store = nil) -> bool {
 	switch constraint {
 	case INT:
 		return is_concrete_integer(concrete)
 	case FLOAT:
 		return is_float(concrete)
+	case RANGE:
+		return is_range(concrete, store)
 	}
 	return false
 }
@@ -1175,6 +1185,7 @@ name :: proc(value: Type) -> string {
 	case BOOL:          return "bool"
 	case INT:           return "int"
 	case FLOAT:         return "float"
+	case RANGE:         return "range"
 	case I8:            return "i8"
 	case I16:           return "i16"
 	case I32:           return "i32"