Shader warnings show up in latest Unity Editor

I've just upgraded to the latest Unity Editor (2021.1.19f1) and now I'm seeing a bunch of shader warnings which previously didn't show. I tried the "Regenerate Shaders and Materials" button, but it didn't help.

Here's an example of one of the warnings:

Shader warning in 'Shapes/Triangle LinearBurn': use of potentially uninitialized variable (tRadial) at Core.cginc(208) (on d3d11)

Compiling Fragment program
Platform defines: SHADER_API_DESKTOP UNITY_COLORSPACE_GAMMA UNITY_ENABLE_DETAIL_NORMALMAP UNITY_ENABLE_REFLECTION_BUFFERS UNITY_LIGHTMAP_RGBM_ENCODING UNITY_LIGHT_PROBE_PROXY_VOLUME UNITY_PBS_USE_BRDF1 UNITY_SPECCUBE_BLENDING UNITY_SPECCUBE_BOX_PROJECTION UNITY_USE_DITHER_MASK_FOR_ALPHABLENDED_SHADOWS
Disabled keywords: INSTANCING_ON SHADER_API_GLES30 UNITY_ASTC_NORMALMAP_ENCODING UNITY_ENABLE_NATIVE_SHADOW_LOOKUPS UNITY_HALF_PRECISION_FRAGMENT_SHADER_REGISTERS UNITY_HARDWARE_TIER1 UNITY_HARDWARE_TIER2 UNITY_HARDWARE_TIER3 UNITY_LIGHTMAP_DLDR_ENCODING UNITY_LIGHTMAP_FULL_HDR UNITY_METAL_SHADOWS_USE_POINT_FILTERING UNITY_NO_DXT5nm UNITY_NO_FULL_STANDARD_SHADER UNITY_NO_SCREENSPACE_SHADOWS UNITY_PBS_USE_BRDF2 UNITY_PBS_USE_BRDF3 UNITY_PRETRANSFORM_TO_DISPLAY_ORIENTATION UNITY_VIRTUAL_TEXTURING