fix smoothstep validation (#3900)

'values' test:
* Infer result type instead of explicitly specifying it.   If specified,
  it's used as the explicit type of the result variable.  Infer it
  instead.  This fixes cases where the type is abstract.
* low == high is an error
  gpuweb/gpuweb#4616

'partial_eval_errs' test:
* Test function foo() must be called from the entry point so
  that overrides are validated.

'early_eval_errs' test:
* Fix argument order: low and high args are first and second.

Bug: crbug.com/351378281

src/webgpu/shader/validation/expression/call/builtin/smoothstep.spec.ts

@@ -51,16 +51,15 @@ Validates that constant evaluation and override evaluation of ${builtin}() rejec
   .fn(t => {
     const type = kValuesTypes[t.params.type];
 
-    // We expect to fail if low >= high as it results in a DBZ
-    const expectedResult = t.params.value1 >= t.params.value2;
+    // We expect to fail if low >= high.
+    const expectedResult = t.params.value1 < t.params.value2;
 
     validateConstOrOverrideBuiltinEval(
       t,
       builtin,
       expectedResult,
       [type.create(t.params.value1), type.create(t.params.value2), type.create(0)],
-      t.params.stage,
-      /* returnType */ concreteTypeOf(type, [Type.f32])
+      t.params.stage
     );
   });
 
@@ -141,6 +140,7 @@ fn foo() {
         code: wgsl,
         constants,
         reference: ['o_low', 'o_high'],
+        statements: ['foo();'],
       });
     }
   });
@@ -159,10 +159,11 @@ Validates that scalar and vector arguments are rejected by ${builtin}() if not f
   })
   .fn(t => {
     const type = kArgumentTypes[t.params.type];
+    const expectedResult = isConvertibleToFloatType(elementTypeOf(type));
     validateConstOrOverrideBuiltinEval(
       t,
       builtin,
-      /* expectedResult */ isConvertibleToFloatType(elementTypeOf(type)),
+      expectedResult,
       [type.create(0), type.create(1), type.create(2)],
       'constant',
       /* returnType */ concreteTypeOf(type, [Type.f32])
@@ -344,7 +345,7 @@ g.test('early_eval_errors')
       t,
       builtin,
       /* expectedResult */ t.params.low < t.params.high,
-      [f32(0), f32(t.params.low), f32(t.params.high)],
+      [f32(t.params.low), f32(t.params.high), f32(0)],
       t.params.stage
     );
   });