Fix type bugs with arrays and pointer subtraction

- Remove superfluous Number cast when the right-hand side is already a numeric
  type.
- Fix pointer subtraction. Force both operands to have bases of equal size.
- Fix alignment of array types.

src/compiler.js

@@ -277,6 +277,8 @@
 
   ArrayType.prototype.lint = function () {
     check(this.base, "array without element type");
+    this.base.lint();
+    this.align = this.base.align;
   };
 
   StructType.prototype.lint = function () {
@@ -294,8 +296,8 @@
       this.fields.push(field = members[i]);
       type = field.type;
 
-      // Recursively lint inline structs.
-      if (type instanceof StructType) {
+      // Recursively lint field types.
+      if (type) {
         type.lint();
       }
 
@@ -843,9 +845,10 @@
       if (rty instanceof PrimitiveType && rty.integral) {
         ty = lty;
       } else if (rty instanceof PointerType && op === "-") {
-        if (lty.assignableFrom(rty)) {
-          ty = Types.i32ty;
-        }
+        check(lty.base.size === rty.base.size,
+              "subtraction with incompatible pointer types " +
+              quote(lty) + " and " + quote(rty));
+        ty = Types.i32ty;
       }
     } else if (BINOP_COMPARISON.indexOf(op) >= 0) {
       if (lty instanceof PointerType && isNull(this.right)) {
@@ -1142,6 +1145,10 @@
       return expr;
     }
 
+    if (rty && rty.numeric) {
+      return expr;
+    }
+
     if (!this.integral) {
       return new CallExpression(new Identifier("Number"), [expr], expr.loc);
     }

src/types.js

@@ -183,7 +183,6 @@
   };
 
   PointerType.prototype.align = u32ty;
-  ArrayType.prototype.align = u32ty;
 
   exports.TypeAlias = TypeAlias;
   exports.PrimitiveType = PrimitiveType;

test/arrays-stack.ljs

@@ -49,22 +49,22 @@ describe('Arrays-Stack', function () {
     assert (arr2[1] === 10);
 
     let ST s;
-    assert (&s - arr === 126);
+    assert (&s - (ST *)(arr) === 126);
   });
 
   it('allocates a struct with an inline array', function () {
     let InlineArrayST s;
     s.arr[5] = 10;
 
     let ST s2;
-    assert (&s2 - &s === 100);
+    assert (&s2 - (ST *)(&s) === 100);
   });
 
   it('allocates a struct with an inline array of structs with arrays', function () {
     let InlineStructArrayST s;
     s.arr[5].arr[5] = 5;
 
     let ST s2;
-    assert (&s2 - &s === 100 * 100);
+    assert (&s2 - (ST *)(&s) === 100 * 100);
   });
-});
+});