Reproduction steps:

1. Add the attached shader "GLES3_GLCore_struct_name_reflection_truncation.shader" to a project
2. Select the shader
3. In the shader's Inspector Window select the dropdown next to "Compile and show code" and tick "Custom" and "OpenGLCore" or "GLES3x"
4. Click the "Compile and show code" button

Expected result:
The "Compile and show code" output for OpenGLCore and GLES3 contains "Vector4 myStruct.m_Float4" in the 'Constant Buffer "NamedCBuffer"' section

Actual result:
The "Compile and show code" output for OpenGLCore and GLES3 contains "Vector4 myStru.m_Float4" in the 'Constant Buffer "NamedCBuffer"' section (2 chars from the struct name are truncated). Also the following error is printed: "Struct 'myStru' is not found." to the Console Window

Note: if the shader constant "anyConstant" is moved from the "NamedCBuffer" to the global scope (as seen in attached "GLES3_GLCore_compiler_crash.shader"), and "Compile and show code" is run for the mentioned GL targets, it will crash the compiler, resulting in an empty output and error:
"Shader compiler: Compile GLES3_GLCore_struct_name_reflection_truncation - <Unnamed Pass>, Vertex Program: Internal error, unrecognized message from the shader compiler process. Please report a bug including this shader and the editor log."

Reproducible in: 2021.2.0a7, 2021.1.0b9, 2020.2.6f1, 2020.1.17f1, 2019.4.21f1
Couldn't reproduce in: 2018.4.32f1