Improve type deduction

Create a new T_UNKNOWN type code and use this for the cases where
we previously abused T_INT.  This means we can now reliably deduce
`int` when we see T_INT.

Fix the deduced result types of unary plus and unary minus which weren't
getting integer promotion applied to them.

Fix the deduced result type of the C++ logical not operator which was
`int` but should be `bool`.

CHANGES.current

@@ -548,8 +548,6 @@ Version 4.2.0 (in progress)
 2023-05-25: olly
 	    C++11 `auto` variables and `decltype()` can now deduce the
 	    type of some expressions which involve literals of built-in types.
-	    Currently int is not supported due to the parser misusing T_INT
-	    for situations where the type isn't actually known.
 
 2023-05-25: olly
 	    #1125 Support parsing C++11 auto variables.  This uses the

Examples/test-suite/cpp11_auto_variable.i

@@ -5,6 +5,9 @@
 static auto t = true;
 static constexpr auto f = false;
 
+static auto zero = 0;
+static constexpr auto one = 1;
+
 static auto la = 1.0L;
 static auto da = 1.0;
 static auto fa = 1.0f;

Examples/test-suite/cpp11_decltype.i

@@ -35,6 +35,15 @@
     DECLARE(a, false);
     DECLARE(b, true);
 
+    // SWIG < 4.2.0 failed to perform type promotion for the result of unary
+    // plus and unary minus, so these would end up wrapped as bool and char.
+    decltype(+true) should_be_int;
+    decltype(-'x') should_be_int2;
+
+    // SWIG < 4.2.0 incorrectly used int for the result of logical not in C++
+    // so this would end up wrapped as int.
+    decltype(!0) should_be_bool;
+
     auto get_number_sum(decltype(i+j) a) -> decltype(i+j) {
       return i+j;
     }

Examples/test-suite/php/cpp11_auto_variable_runme.php

@@ -5,16 +5,28 @@ require "tests.php";
 // No new functions
 check::functions(array());
 check::classes(array('cpp11_auto_variable'));
-check::globals(array('f', 't', 'la', 'da', 'fa', 'lc', 'dc', 'fc', 'pi_approx', 'Bar', 'Bar2', 'Foo', 'Foo2'));
+check::globals(array('f', 't', 'zero', 'one', 'la', 'da', 'fa', 'lc', 'dc', 'fc', 'pi_approx', 'Bar', 'Bar2', 'Foo', 'Foo2'));
 
 check::equal(f_get(), false);
+check::equal(gettype(f_get()), "boolean");
 check::equal(t_get(), true);
+check::equal(gettype(t_get()), "boolean");
 
 t_set(false);
 check::equal(t_get(), false);
 
 check::equal(function_exists('f_set'), false, "f should be constant but f_set() exists");
 
+check::equal(zero_get(), 0);
+check::equal(gettype(zero_get()), "integer");
+check::equal(one_get(), 1);
+check::equal(gettype(one_get()), "integer");
+
+zero_set(42);
+check::equal(zero_get(), 42);
+
+check::equal(function_exists('one_set'), false, "one should be constant but one_set() exists");
+
 check::equal(fa_get(), 1.0);
 check::equal(da_get(), 1.0);
 // PHP doesn't have a native "long double" type, so SWIG/PHP doesn't have

Examples/test-suite/php/cpp11_decltype_runme.php

@@ -31,3 +31,7 @@ check::equal($b->b, true);
 check::equal($b->negate(true), false);
 
 check::equal($b->negate(false), true);
+
+check::equal(gettype($b->should_be_int), "integer");
+check::equal(gettype($b->should_be_int2), "integer");
+check::equal(gettype($b->should_be_bool), "boolean");

Source/CParse/parser.y

@@ -1780,12 +1780,8 @@ static SwigType *deduce_type(const struct Define *dtype) {
   Node *n = Swig_symbol_clookup(dtype->val, 0);
   if (n) {
     return Getattr(n, "type");
-  } else if (dtype->type != T_AUTO && dtype->type != T_INT) {
-    /* Try to deduce the type from the T_* type code.
-     *
-     * Sadly we can't trust T_INT because several places in the parser set
-     * .type = T_INT when it may not be (or even definitely isn't).
-     */
+  } else if (dtype->type != T_AUTO && dtype->type != T_UNKNOWN) {
+    /* Try to deduce the type from the T_* type code. */
     return NewSwigType(dtype->type);
   } else {
     return NULL;
@@ -5304,7 +5300,7 @@ def_args       : EQUAL definetype {
 		 if (skip_balanced('{','}') < 0) Exit(EXIT_FAILURE);
 		 $$.val = NewString(scanner_ccode);
 		 $$.rawval = 0;
-                 $$.type = T_INT; /* This may be a lie. */
+                 $$.type = T_UNKNOWN;
 		 $$.bitfield = 0;
 		 $$.throws = 0;
 		 $$.throwf = 0;
@@ -5324,7 +5320,7 @@ def_args       : EQUAL definetype {
                | %empty {
                  $$.val = 0;
                  $$.rawval = 0;
-                 $$.type = T_INT; /* This is a lie. */
+                 $$.type = T_UNKNOWN;
 		 $$.bitfield = 0;
 		 $$.throws = 0;
 		 $$.throwf = 0;
@@ -6549,7 +6545,8 @@ etype            : expr {
 		       ($$.type != T_LONGLONG) && ($$.type != T_ULONGLONG) &&
 		       ($$.type != T_SHORT) && ($$.type != T_USHORT) &&
 		       ($$.type != T_SCHAR) && ($$.type != T_UCHAR) &&
-		       ($$.type != T_CHAR) && ($$.type != T_BOOL)) {
+		       ($$.type != T_CHAR) && ($$.type != T_BOOL) &&
+		       ($$.type != T_UNKNOWN)) {
 		     Swig_error(cparse_file,cparse_line,"Type error. Expecting an integral type\n");
 		   }
                 }
@@ -6561,7 +6558,7 @@ expr           : valexpr
                | type {
 		 Node *n;
 		 $$.val = $1;
-		 $$.type = T_INT; /* This may be a lie. */
+		 $$.type = T_UNKNOWN;
 		 /* Check if value is in scope */
 		 n = Swig_symbol_clookup($1,0);
 		 if (n) {
@@ -6878,11 +6875,11 @@ exprcompound   : expr PLUS expr {
 	       }
                | MINUS expr %prec UMINUS {
 		 $$.val = NewStringf("-%s",$2.val);
-		 $$.type = $2.type;
+		 $$.type = promote_type($2.type);
 	       }
                | PLUS expr %prec UMINUS {
                  $$.val = NewStringf("+%s",$2.val);
-		 $$.type = $2.type;
+		 $$.type = promote_type($2.type);
 	       }
                | NOT expr {
 		 $$.val = NewStringf("~%s",$2.val);
@@ -6890,7 +6887,7 @@ exprcompound   : expr PLUS expr {
 	       }
                | LNOT expr {
                  $$.val = NewStringf("!%s",COMPOUND_EXPR_VAL($2));
-		 $$.type = T_INT;
+		 $$.type = cparse_cplusplus ? T_BOOL : T_INT;
 	       }
                | type LPAREN {
 		 String *qty;
@@ -6903,7 +6900,7 @@ exprcompound   : expr PLUS expr {
 		 }
 		 $$.val = NewStringf("%s%s",qty,scanner_ccode);
 		 Clear(scanner_ccode);
-		 $$.type = T_INT;
+		 $$.type = T_UNKNOWN;
 		 Delete(qty);
                }
                ;

Source/Swig/stype.c

@@ -109,6 +109,10 @@ SwigType *NewSwigType(int t) {
   switch (t) {
   case T_BOOL:
     return NewString("bool");
+  case T_UNKNOWN:
+    /* Handle like T_INT since we used to just use T_INT where we now use
+     * T_UNKNOWN.
+     */
   case T_INT:
     return NewString("int");
   case T_UINT:

Source/Swig/swig.h

@@ -95,6 +95,7 @@ extern "C" {
 #define   T_VARARGS    39
 #define   T_RVALUE_REFERENCE  40
 #define   T_WSTRING    41
+#define   T_UNKNOWN    42
 
 /* --- File interface --- */