Reject string operands in binary and select ops (KhronosGroup#4077) (KhronosGroup#4079)

Reject string operands in binary and select ops (KhronosGroup#4077). This would previously cause a segfault during SPIR-V codegen

Author: tnibler

Test/baseResults/stringInvalidOps.frag.out

@@ -0,0 +1,40 @@
+stringInvalidOps.frag
+ERROR: 0:5: ':' :  wrong operand types: no operation ':' exists that takes a left-hand operand of type ' const string' and a right operand of type ' const string' (or there is no acceptable conversion)
+ERROR: 0:6: '+' :  wrong operand types: no operation '+' exists that takes a left-hand operand of type ' const string' and a right operand of type ' const string' (or there is no acceptable conversion)
+ERROR: 0:7: '*' :  wrong operand types: no operation '*' exists that takes a left-hand operand of type ' const string' and a right operand of type ' const string' (or there is no acceptable conversion)
+ERROR: 0:7: '+' :  wrong operand types: no operation '+' exists that takes a left-hand operand of type ' const string' and a right operand of type ' const string' (or there is no acceptable conversion)
+ERROR: 4 compilation errors.  No code generated.
+
+
+Shader version: 450
+Requested GL_EXT_debug_printf
+ERROR: node is still EOpNull!
+0:4  Function Definition: main( ( global void)
+0:4    Function Parameters: 
+0:5    Sequence
+0:5      Constant:
+0:5        "def"
+0:6      Constant:
+0:6        "o"
+0:7      Constant:
+0:7        "o"
+0:?   Linker Objects
+
+
+Linked fragment stage:
+
+
+Shader version: 450
+Requested GL_EXT_debug_printf
+ERROR: node is still EOpNull!
+0:4  Function Definition: main( ( global void)
+0:4    Function Parameters: 
+0:5    Sequence
+0:5      Constant:
+0:5        "def"
+0:6      Constant:
+0:6        "o"
+0:7      Constant:
+0:7        "o"
+0:?   Linker Objects
+

Test/stringInvalidOps.frag

@@ -0,0 +1,8 @@
+#version 450
+#extension GL_EXT_debug_printf : require
+
+void main() {
+    true ? "abd" : "def";
+    "o" + "k";
+    "o" + "k" * "l";
+}

glslang/MachineIndependent/Intermediate.cpp

@@ -118,7 +118,8 @@ TIntermSymbol* TIntermediate::addSymbol(const TType& type, const TSourceLoc& loc
 TIntermTyped* TIntermediate::addBinaryMath(TOperator op, TIntermTyped* left, TIntermTyped* right, const TSourceLoc& loc)
 {
     // No operations work on blocks
-    if (left->getType().getBasicType() == EbtBlock || right->getType().getBasicType() == EbtBlock)
+    if (left->getType().getBasicType() == EbtBlock || right->getType().getBasicType() == EbtBlock ||
+        left->getType().getBasicType() == EbtString || right->getType().getBasicType() == EbtString)
         return nullptr;
 
     // Convert "reference +/- int" and "reference - reference" to integer math
@@ -2382,7 +2383,8 @@ TIntermTyped* TIntermediate::addSelection(TIntermTyped* cond, TIntermTyped* true
     trueBlock = std::get<0>(children);
     falseBlock = std::get<1>(children);
 
-    if (trueBlock == nullptr || falseBlock == nullptr)
+    if (trueBlock == nullptr || falseBlock == nullptr ||
+        trueBlock->getBasicType() == EbtString || falseBlock->getBasicType() == EbtString)
         return nullptr;
 
     // Handle a vector condition as a mix

gtests/AST.FromFile.cpp

@@ -215,6 +215,7 @@ INSTANTIATE_TEST_SUITE_P(
         "runtimeArray.vert",
         "simpleFunctionCall.frag",
         "stringToDouble.vert",
+        "stringInvalidOps.frag",
         "struct.error.frag",
         "structAssignment.frag",
         "structDeref.frag",