Forbid case-after-default, tweak error messages (#4831)

* Forbid case-after-default, tweak error messages

* Update tests

* Fix formatting

* Bring back positive version of default-switch.p4 test

frontends/p4/validateParsedProgram.cpp

@@ -188,11 +188,12 @@ void ValidateParsedProgram::postorder(const IR::SwitchStatement *statement) {
     for (auto c : statement->cases) {
         if (defaultFound != nullptr) {
             if (c->label->is<IR::DefaultExpression>())
-                ::error(ErrorType::ERR_INVALID, "%1% has multiple 'default' labels: %2% and %3%.",
-                        statement, defaultFound->label, c->label);
+                ::error(ErrorType::ERR_INVALID, "%1%switch has multiple 'default' labels:%2%%3%",
+                        statement->srcInfo, defaultFound->label->srcInfo, c->label->srcInfo);
             else
-                warn(ErrorType::WARN_ORDERING, "%1%: label following 'default' %2% label.",
-                     c->label, defaultFound->label);
+                ::error(ErrorType::ERR_INVALID,
+                        "%1%switch label %2% follows 'default' label, which is not allowed.%3%",
+                        statement->srcInfo, c->label, defaultFound->label->srcInfo);
             break;
         }
         if (c->label->is<IR::DefaultExpression>()) defaultFound = c;

testdata/p4_16_errors/default-last-switch.p4

@@ -0,0 +1,16 @@
+control ctrl() {
+    action a() {}
+    action b() {}
+
+    table t {
+        actions = { a; b; }
+        default_action = a;
+    }
+
+    apply {
+        switch (t.apply().action_run) {
+            default:
+            b: { return; }
+        }
+    }
+}

testdata/p4_16_errors/issue3611.p4

@@ -9,11 +9,10 @@ control c()
   }
   apply {
    switch(t.apply().action_run) {
-      default: {}
       1: {} // { dg-error "" }
-      default: {}
       a: {}
       a: {}
+      default: {}
     }
   }
 }

testdata/p4_16_errors_outputs/default-last-switch.p4

@@ -0,0 +1,22 @@
+control ctrl() {
+    action a() {
+    }
+    action b() {
+    }
+    table t {
+        actions = {
+            a;
+            b;
+        }
+        default_action = a;
+    }
+    apply {
+        switch (t.apply().action_run) {
+            default: 
+            b: {
+                return;
+            }
+        }
+    }
+}
+

testdata/p4_16_errors_outputs/default-last-switch.p4-stderr

@@ -0,0 +1,9 @@
+default-last-switch.p4(11): [--Werror=invalid] error: switch label b follows 'default' label, which is not allowed.
+        switch (t.apply().action_run) {
+        ^^^^^^
+default-last-switch.p4(13)
+            b: { return; }
+            ^
+default-last-switch.p4(12)
+            default:
+            ^^^^^^^

testdata/p4_16_errors_outputs/issue2525.p4-stderr

@@ -1,4 +1,4 @@
-issue2525.p4(64): [--Werror=invalid] error: SwitchStatement has multiple 'default' labels: DefaultExpression and DefaultExpression.
+issue2525.p4(64): [--Werror=invalid] error: switch has multiple 'default' labels:
         switch (t.apply().action_run) {
         ^^^^^^
 issue2525.p4(66)

testdata/p4_16_errors_outputs/issue3611.p4

@@ -15,16 +15,14 @@ control c() {
     }
     apply {
         switch (t.apply().action_run) {
-            default: {
-            }
             1: {
             }
-            default: {
-            }
             a: {
             }
             a: {
             }
+            default: {
+            }
         }
     }
 }

testdata/p4_16_errors_outputs/issue3611.p4-stderr

@@ -1,21 +1,9 @@
-issue3611.p4(13): [--Wwarn=ordering] warning: 1: label following 'default' DefaultExpression label.
+issue3611.p4(12): [--Werror=type-error] error: 1: 'switch' label must be an action name or 'default'
       1: {} // { dg-error "" }
       ^
-issue3611.p4(12)
-      default: {}
-      ^^^^^^^
-issue3611.p4(13): [--Werror=type-error] error: 1: 'switch' label must be an action name or 'default'
-      1: {} // { dg-error "" }
-      ^
-issue3611.p4(14): [--Werror=type-error] error: DefaultExpression: multiple 'default' labels DefaultExpression
-      default: {}
-      ^^^^^^^
-issue3611.p4(12)
-      default: {}
-      ^^^^^^^
-issue3611.p4(16): [--Werror=type-error] error: a: 'switch' label duplicates a
+issue3611.p4(14): [--Werror=type-error] error: a: 'switch' label duplicates a
       a: {}
       ^
-issue3611.p4(15)
+issue3611.p4(13)
       a: {}
       ^

testdata/p4_16_samples/default-switch.p4

@@ -9,8 +9,8 @@ control ctrl() {
 
     apply {
         switch (t.apply().action_run) {
-            default:
-            b: { return; }
+            b:
+            default: { return; }
         }
     }
-}
+}

testdata/p4_16_samples_outputs/default-switch-first.p4

@@ -12,8 +12,8 @@ control ctrl() {
     }
     apply {
         switch (t.apply().action_run) {
-            default: 
-            b: {
+            b: 
+            default: {
                 return;
             }
         }

testdata/p4_16_samples_outputs/default-switch.p4

@@ -12,8 +12,8 @@ control ctrl() {
     }
     apply {
         switch (t.apply().action_run) {
-            default: 
-            b: {
+            b: 
+            default: {
                 return;
             }
         }

testdata/p4_16_samples_outputs/default-switch.p4-stderr

@@ -1,9 +1,3 @@
-default-switch.p4(13): [--Wwarn=ordering] warning: b: label following 'default' DefaultExpression label.
-            b: { return; }
-            ^
-default-switch.p4(12)
-            default:
-            ^^^^^^^
 default-switch.p4(1): [--Wwarn=unused] warning: Control ctrl is not used; removing
 control ctrl() {
         ^^^^