Avoid error cascades when casting out-of-range scalar values.

Previously, when attempting to cast a huge value to an int, SkSL would
report an error, then return the IR for
`ScalarCast(Int, FloatLiteral(huge-value))` . Now, to minimize the blast
radius of the error, we report the error but return `IntLiteral(0)`.
We've already reported an error, so there's no need to preserve the
value, and zero is less likely to produce follow-up errors.

(A similar approach is used here and worked well: https://osscs.corp.google.com/skia/skia/+/main:src/sksl/ir/SkSLConstructorCompoundCast.cpp;l=57-59)

Change-Id: Ie8e8d48380cb963466d1f47d123d64e3301cf87c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/499563
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>

src/sksl/ir/SkSLConstructorScalarCast.cpp

@@ -70,12 +70,15 @@ std::unique_ptr<Expression> ConstructorScalarCast::Make(const Context& context,
     arg = ConstantFolder::MakeConstantValueForVariable(std::move(arg));
 
     // We can cast scalar literals at compile-time when possible. (If the resulting literal would be
-    // out of range for its type, we report an error and return the constructor. This can occur when
-    // code is inlined, so we can't necessarily catch it during Convert. As such, it's not safe to
-    // return null or assert.)
-    if (arg->is<Literal>() &&
-        !type.checkForOutOfRangeLiteral(context, arg->as<Literal>().value(), arg->fLine)) {
-        return Literal::Make(line, arg->as<Literal>().value(), &type);
+    // out of range for its type, we report an error and return zero to minimize error cascading.
+    // This can occur when code is inlined, so we can't necessarily catch it during Convert. As
+    // such, it's not safe to return null or assert.)
+    if (arg->is<Literal>()) {
+        double value = arg->as<Literal>().value();
+        if (type.checkForOutOfRangeLiteral(context, value, arg->fLine)) {
+            value = 0.0;
+        }
+        return Literal::Make(line, value, &type);
     }
     return std::make_unique<ConstructorScalarCast>(line, type, std::move(arg));
 }

tests/sksl/errors/ArrayOfInvalidSize.glsl

@@ -5,7 +5,7 @@ error: 2: array size must be positive
 error: 3: array size must be positive
 error: 4: expected 'int', but found 'float'
 error: 5: integer is out of range for type 'int': 4000000000
-error: 5: array size must be an integer
+error: 5: array size must be positive
 error: 6: expected 'int', but found 'bool'
 error: 7: expected 'int', but found 'bool'
 error: 8: expected 'int', but found 'int2'

tests/sksl/errors/Ossfuzz40660.glsl

@@ -4,7 +4,6 @@ error: 1: unknown identifier 'f'
 error: 1: expected ')' to complete function arguments, but found '`'
 error: 1: expected ')' to complete expression, but found '`'
 error: 1: integer is out of range for type 'int': 3689348940
-error: 1: integer is out of range for type 'int': 3689348940
 error: 2: expected ']' to complete array access expression, but found ''
 error: 2: expected ';', but found ''
-7 errors
+6 errors

tests/sksl/errors/Ossfuzz44045.glsl

@@ -1,6 +1,5 @@
 ### Compilation failed:
 
 error: 1: integer is out of range for type 'int': 3976000000
-error: 1: integer is out of range for type 'int': 3976000000
-error: 1: array size must be an integer
-3 errors
+error: 1: array size must be positive
+2 errors